Global Warming?

I happen to work with several vehement, well-spoken neo-conservatives who are able to trot out lots of nice sounding facts about the non-existence of global warming. The thing is, the pro-global warming group seems to be able to do the same thing. As a layperson who hasn't read a great deal about climate and atmospherics, I'm curious to hear the arguments about who is right. Is human caused global warming fact or farce?

Hi Badger

Yes, global warming is a big issue. There have been some good books written on the subject & you might want to start there.

Winds of Changeby Eugene Linden
The Weather Makers by Tim Flannery & The Weather by Anthony Smith all concentrate on presenting the facts without sensationalism.

There are more out there. this is a popular topic.

When people talk about "global warming", they can mean three different things:

1) Is the overall atmospheric temperature of the Earth increasing?

2) Are human activities solely or mostly responsible for this?

3) Should "we" do anything about it?

Extremists on either end of the spectrum only accept a "yes" or "no" answer for all three, else you're a greed-driven denier unwilling to accept settled science or an enviroloon that wants to force the entire planet into a socialist Stone Age. My personal answers are 1 - yes, 2- maybe, 3 - no, which allows me to get into enjoyable screaming arguments with almost anybody.

One could argue from almost any viewpoint about whatever's causing major earth/climate changes or how much is due to human industry etc. It's complex enough to pick any side of an argument and make it sound good. But it's ironic to me that people would argue about the whys rather than to cooperate in such a way as to seek solutions. Like arguing about the color of the locomotive that's bearing down on those tied to the tracks.
Nature has a way of self-healing though it has to be let alone to do so. Heavily polluted lakes can clear up in time IF all polluting is halted. But most efforts to halt polluting seem token and too little in the face of industrialization's history and status.

The fundamental atmospheric chemistry is very very simple.

CO2 (and various other gases methane etc) are transparent to solar radiation. (ie you can see the sun). When this sunlight hits the earth some of it is converted to IR radiation (known as heat). CO2 and the other gases are not transparent to IR radiation. hence the heat can't escape. If you increase the amount of CO2 in the atmosphere then the amount of heat trapped on earth will increase.

You can test this in a school physics or chemistry laboratory yourself.

However, life is not as simple, and weather systems even less so. The proportion of CO2 (and equivalents) in the atmosphere is small, and the human contribution smaller still. There is no doubt that the human contribution has increased. However it is less clear if this is significant. The IPCC concludes it is highly likely that it is.

The IPCC reports are quite accessible to lay readers, and about as unbiased source as you will find these days.

How and on what timescale the future weather will respond to a significant change in atmosphere chemistry is open to complex argument, BUT if you are used to weather systems x, then you will undoubtably find life harder if the weather changes to y! So act today to make tomorrow less hard for everybody!

The fundamental problem to me is not if global warning is happening, or if it's anthropogenic, but the idea that it's a "problem" that must be "solved". Archaeology and paleontology reveal lots of evidence that the planet was once a lot warmer - or colder - than it is now. Yes, these events caused organisms to go extinct and changed ecosystems, but others moved into those places.

A particular item in the litany that gripes me the most is the repeated claim that "we" must take action to "save the planet". Save it from what? This is the same sort of hubris that once allowed rampant destruction of natural features - but now being applied in the opposite direction. The planet is 4.5Gy or so old, and we've been around for at most about 0.007% of that time. Why would anybody think that this vanishingly small fraction of Earth history is the "definitive" planet that has to be "saved"? I'm all for a lot of environmentalism, but I'm for it for entirely selfish purposes - because I might want to see a grizzly bear or walk through a wilderness, not because some abstract semireligious Mother Nature requires grizzly bears and wilderness and I'm just devoting myslef to Her cause.

If we really wanted to "save the planet, we should be doing are best to restore it to what it's been for most of its history - a reducing atmosphere, sterile continents, and an ocean inhabited only by procaryotes.

Yep, we don't need to save the planet. We just need to keep it reasonably habitable. As weather patterns change, it won't be reasonably habitable for many many people. Lots of Bangladeshis and Africans will be displaced and many will die. Also plenty of species will go extinct, which some of us do find objectionable. So, I do think we should take action to stop or slow global warming.

The folks in Greenland are OK with global warming right now. They are able to grow crops that wouldn't grow in Greenland for centuries.

As for the non-existence of global warming -- Hah. The evidence is very very strong, and the naysayers are mostly paid shills of the energy companies. Among climatologists, there is an overwhelming consensus that global warming is underway, and that human emitted CO2 is the main cause. That said, most of the effects until now have been on the northern polar region -- with resulting disruptions to produce unusual weather. The average temperature increase in temperate zones has been a fraction of a degree. But the effect on the Arctic has been much faster than scientists predicted. La Nina is moderating the temperature change in temperate zones, but it will go away one of these days.

I think I should clarify my question: Even the people I work with agree that it's getting warmer. The question mainly is: are humans the cause of global warming, and if so should we do anything?

Thanks for all the different answers!

Well, let's see:

Humans, rats and cockroaches are pretty good a finding places on the planet that are habitable. I would note that the Bangladeshis and Africans are already living in the warmest parts of the planet, and seem to be doing quite well there (at least in terms of population); in fact, human population (although not quality of life) is postively correlated to average temperature.

So far, attempts to "stop global warming" have, thankfully, been mostly talk and no action. However, some of the suggestions made are potentially pretty diasastrous. It's interesting that both economists and environmentalists have been predicting disaster for decades: the environmentalists if we don't take all sorts of economically relevant actions, and the economists if we do. So far, both sides have been wrong. The environmental horrors predicted by Paul Ehrlich and the like (IIRC, the Earth was supposed to be uninhabiable by 1985) have not come to pass; however, neither has the collapse of world economy predicted if various environmental laws were put into effect. Apparently both the environment and the economy are more robust than the experts thought. However, I do agree that there are "tipping points" for both environment and economy beyond which they will collapse (collapse as far as humans are concerned; lots of other species will be perfectly happy); I just happen to think that that the economic tipping point is closer than the environmental one. My reason for believing this is that lots of people - the climatologists mentioned, for example - are perfectly confident that they can predict the state of the global climate 50 years from now, but nobay has a clue what the international markets are going to do tomorrow. Therefore, by proposing various measure to deal with global warming by affecting the economy, we're messing around with something we don't understand. It's not just that I'm in knee-jerk opposition to any environmental measures - I'm a professional in the environmental field. It's just that I've seen too many environmental regulations that actually make things worse instead of better because the consequences were unknown. We're already seeing this to a certain extent; food prices for American corn (that's maize if you happen to be from the Old World) have gone through the roof because much of the crop that was formerly sold on the world market is now going to make ethanol. That's causing hunger - and perhaps famine in the future - to those same Bangladeshis and Africans we're trying to "save" from global warming.

"Species extinction" is also a debatable concept. For one thing, "species" is a human concept, not a natural one - a lot of animals and plants we think of as distinct species are quite willing to interbreed and hybridize in the wild. Further, species are supposed to go extinct - that's the only reason we're here to worry about them in the first place. Again, I'm sorry we lost passenger pigeons and Carolina parakeets - but that's a personal feeling on my part, not some sort of quasi-religious belief in the sanctity of Nature. I'm sorry we lost wooly mammoths and American lions and short-faced bears and titanotheres and carnosaurs, too - but I would want any of those things turning up in my back yard. I'd also note that since the end of the Pleistocene the North American climate has warmed by somewhere between 5 and 16 degrees F, depending on whose data you believe, but those animals that went extinct were not done in by the climate change - they had survived as many as sixteen similar episodes - but by human predation. The ones that didn't go extinct are doing just fine in the warmer climate - pronghorns and elk/wapiti and grizzly bears were all once wandering around in the same climate that supported mammoths. Even polar bears, the poster child of a lot of environmental extremists, are adapted to a warmer climate; they appear to have evolved as recently as 10000 years ago (there are many paleomammalogists that would disagree with that, though, and put polar bear speciation as far as 100000 years ago; polar bear fossils are awfully hard to distinguish from grizzly bears and the animals will hybridize, even in the wild, so it's unclear when the lineages split). They never would have been able to make a go of it at the height of the Pleistocene glaciation.

As far as being a paid shill of the energy companies - I'm still waiting for my check from Exxon. (I realize that you were not speaking of me personally). However, just as when one species goes extinct there's alwasy another one ready to move into the niche, regulations that are bad for one corporation are generally good for another. I don't know if you're old enough, but when I was growing up there were plenty of "Mom and Pop" gas stations that were able to make a living. Environmental regulations to prevent leaking underground tanks put all of them out of business - they couldn't afford the compliance upgrades necessary. The petroleum market is now dominated by a few large corporations. Similarly the move to use more ethanol in fuel has been a windfall for large agribusiness.

At any rate, I won't live long enough to see the predicted dire effects of global warming - but while I last things ought to be interesting no matter what happens.

Seknahkt, I am trying to understand your position, here, but it isn't looking too appealing. I sum it up this way: We don't need to do anything about global warming because (a) you won't be around when it really hits, and (b) a bunch of species goes extinct, so what, stuff happens, and (c) it would be utter disaster to try to do anything about it. This might not be a fair summary, but, hey, what am I missing?

I will answer (c): Scientific American recently gave a pretty good analysis on how a 45 year transition to solar power could be financed with about a $450B subsidy over those years (about 1/4 the eventual total cost of the Iraq war, for comparison). That isn't an utter disaster. Of course, other nations would have to take similar measures, but right now the US is laggard number 1 in doing something about global warming.

BTW, I wouldn't be too sure that global warming won't affect you in your lifetime. I see you are from Colorado. Expect big droughts.

Addendum: The way to combat global warming is actually pretty simple, and we ought to do most of these things for other reasons.

(1) Burn less coal and oil, and produce more energy from solar, wind, and possibly nuclear.
(2) Use energy more efficiently. No hummers. Lots of commuter trains.
(3) Plant lots of trees, and stop deforestation.

There are other approaches, which are a little more controversial:

-- Fertilize the ocean so it can soak up more CO2
-- Shoot certain reflective particulates into the upper atmosphere with rockets

We might need to try these, but I wouldn't want to count on them.

Other way around; most climate models predict increased rain and snowfall in Colorado due to global warming - greater temperatures bring more evaporation in the Pacific and end up dumping more precipitation on the Rockies. Not that more precipitation won't potentially make things different, as well - might end up with forest taking over the Great Plains again.

I don't know that attempts to "fix" global warming will be an utter disaster; they might work out just fine. However, I don't think anyone else really knows, either. We're already seeing relatively minor attempts to do things having unintended consequences - like increased corn production for ethanol in the US raising food prices in Africa. The history of the US is full of examples where things that seemed like a good idea at the time - supressing forest fires, killing off predators in national parks, turning Tulsa into a seaport - ended up being not such a good idea after all. But the best and brightest of the time were all in favor of them.

As far as species going extinct - well, yes, stuff does happen. I was originally trained as a paleontologist and tend to take a long view on things like that. There's a lot of paleoclimatological and archaeoclimatological evidence for entirely natural atmospheric and climate fluctuations way larger than even the worst global warming predictions (for example, the atmosphere seems to have been about 4% carbon dioxide in the Devonian - one presumes that wasn't due to Icthyosteaga driving around the swamps in SUVs). Yep, some things go extinct, and others take their place. Thats the way things work.

The idea that we are supposed to save every single species that just happens to exist during our own insignificant tenure on the planet is sort of a reverse hubris from the old belief that everything out there was ours to kill in whatever quantity we wanted. I also note that people's desire to "save" species is directly proportional to how cute they are. I wonder if there's enough of that to actually exert selection pressure - maybe in the future all mice will look like Mickey; we're the dominant force in their environment and it would make sense for them to adapt that way so they would be too cute to trap. I'm not so sure about the little white gloves, though. :)

> 12 Let's admit that whatever we do to solve the global warming problem should be thought through. Corn ethanol for cars was not thought through, and it is a bad idea. However, banning freon was a very good and successful idea, and over time it will allow the ozone layer to recover. This is a good thing. It was achieved through international cooperation and legal regulation, so such things can happen and succeed. We need to repeat that success for the emissions of CO2 and other greenhouse gases.

I think conversion to solar and wind, and increased conservation, will work well and will have a lot of positive side effects, like less mercury in water, less acid rain, less massive destruction of the local environment as currently occurs with most strip mining operations, fewer carcinogens in the atmosphere, and less money exported to petroleum potentates. I think there is plenty of evidence that if we don't take some of these actions, the result will be very bad indeed.

You seem to elide over the difference between saying we must save every species and saying that we should not cause, by our own actions, the extinction of a great many species. There is a difference, I think. True, mass extinctions have occurred in the past, due to natural causes. That does not make it any more tolerable for us to cause one ourselves.

I kind of think the global warming issue is ironically similar to the war in Iraq. I both cases we had experts warning us of disaster if we didn't do something. In both cases negative or skeptical voices were silenced or disregarded by calling them "unpatriotic" or "shills of the energy industry". In both cases, the "experts" were very reluctant to share the data that they used to draw their conclusions.

Then, on the flip side, some of the results of the war in Iraq were, seemingly, positive. Saddam Hussein really was a mass murderer and the desert really was full of mass graves (of course there are fanatics who insist that all of that is faked, just as there are fanatics that insist that all of global warming is faked).

The problem, of course, is how can we tell how much good, if any, we actually did in Iraq, and how much good, if any, global warmings measures are working. We have no statistical controls; there's no second Iraq that we didn't invade that we can compare to the one that we did, and no second climate that we can compare to the one we've got. Thus, it can be argued that Iraq would be much worse off if we hadn't went to war, and the climate would be much worse if we hadn't issued control measures, but we can never really be sure; we might have made things worse for Iraq by what we did, and measures intended to ameliorate climate change might make things worse.

It's that last point that is the telling one, in my opinion. It's not that I object to anti-global warming measures out of philosophical principles, it's that I am not at all sure that they will actually work, and not even that they will work, but that they won't make things worse. Many of these things sound foolproof - what possible harm could increased use of solar energy do (as one example)? Well, I don't know, and I don't think anyone else has really thought it out. As I said, history is full of things that seemed like great ideas at the time, and yet had all sorts of unforseen consequences. We see the European Union enthusiastically accepting what they call the "precautionary principle", when any new technology is considered guilty until proven innocent (and often not even then), but nobody ever applies the precautionary principle to economics or regulation, which have the potential to harm many more people than trace amounts of phthalates in water bottles.

I've been in the environmental field for decades now, and I started out as a knee-jerk/tree-hugging/Save the Whales/Baby Seals/Furbhish Lousewort enthusiast. Actual experience with the was environmental issues are handled has left me fairly cynical - perhaps too cynical, I suppose. One of the problems with environment work is that it's always your job to imagine the worst thing that could happen and act to prevent it; I am soundly hated by many in my organization because I've caused them to go over budget on projects to deal with environmental issues that turned out to be insignificant.

I suppose that might be the worst case scenario in the global warming situation; if climate change doesn't turn out to be as bad as the most extremist climate modelers have predicted, and burdensome and expensive regulations are introduced, people will lose faith in the ability of scientists to correctly predict any environmental problems.

On to species - well, we are natural. We evolved right here, just like all the species that we want to protect. Again, I have no objections at all to keeping marginal species intact - but in many cases that's just as artificial as killing them off. I don't like it when the preservation of species is treated as some sort of sacred duty, rather than being part of an economic give-and-take like any other human activity.

The time perspective is also important. When people think about the "natural" environment of North American, they always seem to mean the way it was in 1492. That, in fact, was a very unnatural environment (if you use "unnatural" in the sense of "unmodified by humans", which is the way most people seem to). Native Americans had already killed off a lot of the large mammal fauna and extensively modified native vegetation on most of the continent by seasonal burning. My question is why is any particular year the standard for "natural"? Why not 1300, or 600, or -1000, or -8000, or -12000? Again, I see it as reverse environment hubris; we used to imagine we were a special part of Creation; now we imaging we are specially outside the natural system.

On another note - I'm relatively new here so I'm not up to speed on LibraryThing social conventions. Is this sort of discussion appropriate for this site and forum? Should it go off-line? Is anybody else reading this, or are is it just boring people and using up bandwidth?

>14 setnahkt: I don't know if anyone else is reading. The discussion might get a little more action over in the Pro & Con group, or else maybe not. Or maybe you and I should just go quiet to see if anyone else cares.

BTW, a UN study group just found that 70% of all plant species and 25% of all animal species were threatened with extinction, primarily from human activity. IMHO, that's bad. We can't return to a primeval state of nature, but if we lose some large percentage of threatened species, we will have destroyed quite a lot.

I think your analogy of global warming and the Iraq war is a real stretch. The Iraq war wasn't thought through and was based for the most part on lies. If you really think we can keep burning coal and oil at an ever accelerating rate, and that measures to change this would make things worse, you need to make a good argument. Your argument so far just seems to be that any conscious step in any situation can make things worse -- true so far as it goes, but at most a thin excuse for inaction.

>15 jmcgarve:...Or maybe you and I should just go quiet to see if anyone else cares....

deal

I would say this sort of discussion is appropriate here.
We're dealing with literature after all, and really this discussion should be appropriate anywhere considering its importance ( if you consider the future of mankind important)

Setnahkt, I agree extinction is a natural phenomenon. I have a question: Have humans had to cope with a rate of loss of biodiversity as high as at present at any time throughout human history?

Can humans cope with a rapid rate of change? Can we adapt to it?

Call me selfish, but I don't like the effects of overpopulation, pollution and loss of biodiversity. I will do all I can to alleviate these effects. I guess we can play scientific catchup in debating greenhouse, but if we're wrong do we really want to miss the bus?

"Is this sort of discussion appropriate for this site and forum? Should it go off-line? Is anybody else reading this, or are is it just boring people and using up bandwidth"

the group has 58 memebers, well above the mean for an LT group even if it's small compared to the big groups. Most of these are likely to read the topic, and there'll be a few drive readings too. But don't kid yourself that this discussion is reaching a wide audience. It absolutely is appropriate for the forum, though a few touchstones to sources* wouldn't go amiss.

"nobody ever applies the precautionary principle to economics" I'm sure is wrong.

There are a lot of estimates out there to the cost of global warming, and the cost of many of hte solutions is far cheaper, which should be a no-brainer. However they are borne by different parties. And for many other solutions they are a good idea anyway even if there wasn't global warming. Solar/wind power, public transport, reducing and recycling are all sensible from a resources consumption point of view and a household economic point of view.

*yes I know I haven't included any either ;-)

Setnahkt, I agree extinction is a natural phenomenon. I have a question: Have humans had to cope with a rate of loss of biodiversity as high as at present at any time throughout human history?

We don't know what the rate of loss of biodiversity is. There are all sorts of "studies" that quote immense numbers for species extinction. But I'm somewhat dubious of the numbers. The US Endangered "Species" Act, as an example, protects not just species (which at least have a biological definition - not a very good one, but still a definition) but "subspecies" and "populations" (for vertebrates) as well. "Subspecies" hasn't actually been used by serious taxonomists for years, and "population" is even more speculative. Many of the things that are claimed to be "species" probably aren't. (As a local example - there is a huge effort to protect the Preble's Meadow Jumping Mouse (known as PIMJIM) which turns out to be a "subspecies" of a common mouse. The subspecies designation was based on five skins - not even whole animals - collected in the 1950's).

I'm all for protection of nature - I like the outdoors as much as the next guy, although I happen to think we should be protecting endangered habitats rather than endangered species. What I object to the is quasireligious tone it sometimes takes. When we "protect" a species, we are interfering with a natural process just as if we deliberately drove it to extinction. That's fine - but it should be understood that we are doing something for human purposed, not for "Mother Nature".

Nobody claiming biodiversity loss is actually counting extinct species - they're making estimates based on biogeography and habitat loss.

Can humans cope with a rapid rate of change? Can we adapt to it?

Well, depending on whose data you accept, the planet warmed between 8 and 16 degrees (F) at the end of the Pleistocene. Humans seemed to do just fine with that. In general, we seem to have a much greater difficulty dealing with sociological change than environmental change; if you consider the difference between human society (in terms of, say, lifespan, attitude toward race and gender, etc.) in 1900 and 2000 that way more of a change than is expected to come from global warming.

Call me selfish, but I don't like the effects of overpopulation, pollution and loss of biodiversity. I will do all I can to alleviate these effects. I guess we can play scientific catchup in debating greenhouse, but if we're wrong do we really want to miss the bus?

I'm not especially fond of "overpopulation" myself; however, I note cynically that almost everybody considers that the Earth wasn't overpopulated until after they were born, and that there's always the option to reduce the population by one but very few people seem to be taking that route. In short, overpopulation is a problem with "other people" that they have to solve. Historically, the best way to deal with overpopulation is economic development - when people realize that having lots of children hampers their life style rather than enhancing it.

The elimination of "pollution" is something that can also go to far. Ever since we invented control of fire - which probably happened when we were a different species - humans have adapted to air pollution. Although we tend to think of our Neolithic ancestors as living out in the wide open spaces, they probably actually spent most of their time in yurts or teepees or caves or whatever, breathing fumes from animal dung fires. Almost all preserved bodies (mummies) from ancient times that have lung tissue show some degree of anthracosis, and many skulls show pitting of the palate characteristic of a lifetime of smoke inhalation. There is evidence that the increasing incidence of asthma is caused by insufficient exposure to "pollutants" at a young age - the immune system doesn't get a change to develop. (It is, of course, possible to go to far - I wouldn't want to live in a city that used brown coal for power).

I'm not opposed to many proposed or actual environmental measure, but it seems like too often these measures are actually worse than useless - they exacerbate environmental problems, usually in unsuspected ways, rather than solving them. In the American West, killing large predators was once sanctioned as a "conservation" measure, as was elimination of forest fires. Both those decision came back to haunt us latter.

"nobody ever applies the precautionary principle to economics" I'm sure is wrong.

People certainly attempt to, arguing that particular measures for some presumed public benefit will cost too much. However, to the best of my knowledge, there isn't a formal proposal anywhere to introduce a sort of "Enconomic Impact Statement" that attempts to follow the same sort of analysis that environmental impact statements do. Economics has an environmental impact of its own; there's no particular secret that the poorest countries usually have the most screwed-up environments.

There are a lot of estimates out there to the cost of global warming, and the cost of many of hte solutions is far cheaper, which should be a no-brainer.

People certainly claim various things are cheaper. But those claims often ignore all sorts of hidden costs (I mentioned the hidden costs of using corn for ethanol production above).

However they are borne by different parties. And for many other solutions they are a good idea anyway even if there wasn't global warming. Solar/wind power, public transport, reducing and recycling are all sensible from a resources consumption point of view and a household economic point of view.

Are they? I've seen it suggested lots of times that recycling is more expensive - and consumes more energy - than just discarding things. It depends on what's being recycled and where you're doing it, of course. Metal recycling almost always makes sense; glass and paper are dubious. It makes sense to use disposable products in the American west, where landfill space is abundant but water (for washing things for resuse) is scarce; the reverse is true east of the Mississippi. The general problem with recycling in the US is that it's labor intensive, and labor's expensive here. A lot of what we think of as "recycled" is shipped to Asia. Does the cost - economic and energy wise - of transporting a freighter full of waste to China really justify the effort to recycle it? I'm skeptical of the numbers.

I'm all for public transit - I work for a transit district. However, if we had to charge what it actually costs us to operate, nobody would ride. Instead we're subsidized by sales tax. When the economy goes bad - like now - our sales taxes revenue goes down. And each $0.01 increase in the cost of a gallon of Diesel fuel is $100K/yr for us.

Sounds like human activities have already caused enough extinctions to be noticeable in the fossil record, though this is the first time we will have done it via climate change, which is a big factor historically (usually due to natural causes, including relatively short-lived changes due to volcano eruption or asteroid impact): http://uk.encarta.msn.com/encyclopedia_761570369/Extinction.html

Seven Great Lakes fish species became extinct in the 20th c, I think, plus many more subspecies such as Lake Erie's blue pike, a kind of walleye. Overfishing, pollution, and exotics were probably responsible for the extinctions, but climate may now be playing a part. For example, small changes in temperature (such as Mt Pinnatubo's eruption causing colder winters for one or two years) can noticeably change the fortunes of remaining populations. And the demise of Lake Ontario's American Eel may be due in part to ice-melt changes in ocean salinity and thus in prey items available to elvers migrating to Lake Ontario from their birthplace in the Sargasso Sea--scientists are just beginning to tease out the climate factor (in addition to pollution, overfishing, hydrodams, etc.).

One wag has named our period the "Homogecene" because global commerce has introduced "weedy" species widely, allowing them to compete with previously sheltered native species. For example, the Eurasian zebra mussel was introduced in ships' ballast to the Great Lakes where it outcompeted native clams and quickly accessed the Mississippi River, one of the richest repositories of bivalve/clam species in the world.

It is thought that the stress of climate change will speed along this homogenization process, leaving our kids with a much reduced natural heritage.

Seven Great Lakes fish species became extinct in the 20th c, I think, plus many more subspecies such as Lake Erie's blue pike, a kind of walleye.

Again, I'm pretty dubious about "subspecies". A subspecies is whatever a sufficiently convincing taxonomist thinks is a subspecies. It is entirely a human concept and has no natural meaning.

Overfishing, pollution, and exotics were probably responsible for the extinctions, but climate may now be playing a part.

The Great Lakes are extremely recent (the Great Lake basins are probably older). It's quite possible there were humans on the continent before the Great Lakes existed. Since the lakes were scoured down to the bedrock (and presumably sterilized) by Pleistocene glaciation, all the animals in them are "exotic". To describe a particular organism as "exotic" is rather anthropocentrist. Why should we consider zebra mussels "exotics" just because they developed adaptations that made them especially good at hitching rides on ships? Like any other organism, they evolve to expand their niche as much as possible. Wanting to kill off zebra mussels to preserve native species is fine, but it's not "preserving a natural environment" - it's preserving an environment that humans happen to like, and which is no more "natural" or "unnatural" than any other.

For example, small changes in temperature (such as Mt Pinnatubo's eruption causing colder winters for one or two years) can noticeably change the fortunes of remaining populations.

Agreed. Lots of species are hanging on by the skin of their teeth. Cave-dwelling organisms might vanish if their microclimate changed by a degree. Others - like rats, cockroaches, and people - are pretty resiliant.

And the demise of Lake Ontario's American Eel may be due in part to ice-melt changes in ocean salinity and thus in prey items available to elvers migrating to Lake Ontario from their birthplace in the Sargasso Sea--scientists are just beginning to tease out the climate factor (in addition to pollution, overfishing, hydrodams, etc.).

What about just bad luck in the genetic sweepstakes? There are certainly species made extinct by humans. However, a whole lot of species - most of them - went extinct long before anything even vaguely resembling a human existed.

Life on the planet has been around for maybe 3.5Gy. Recorded history is about 5K years. Basing decisions on what the "normal" climate and "normal" species diversity is from our history is equivalent to deciding a US presidental election based on the votes of 4 people. (Well, maybe in Florida.... ;)) We have a hubristic tendency to believe that the environment we happen to live in right now is the "correct" one, even though on a geological time scale we are no more than an eyeblink.

There are already organisms that have adapted to our "pollutants"; one species pollutant is another's windfall. In the environmental field there are bacteria and fungi that eat or respire Diesel fuel, tetrachloroethene, pentachlorophenol, arsenic, and nylon.

It strikes me that a lot of the activism surrounding supposedly environmentally deleterious human activites comes from people who are not quite comfortable with the age of the Earth and organic evolution through natural selection. The fixation on individual species and subspecies is reminiscent of the Creationist fixation with immutable "kinds" rather than evolving organisms, and the idea that things that happen during our tenure on the planet is of vital importance is parallel to Archbishop Usher and his Creation on October 23, 4004 BC.

There's a pretty good article on assessing the economic value, or lack of it, in combating global warming in the latest Scientific American:

http://www.sciam.com/article.cfm?id=the-ethics-of-climate-change

There are several problems with trying to figure this out. The first is to figure out how much to discount the value of the future. In general, wealth has been growing, and if these trends continue, we may expect our descendants to be more wealthy than we are, so they are therefore better able to pay for global warming abatement than we are. One economist basically says that we should discount the future at prevailing interest rates of about 6%, which basically means that assets 50 years in the future aren't worth diddly today, so we shouldn't worry about global warming. (I find his opinion silly. Real interest rates, not including inflation, are near 0 worldwide. It doesn't make sense to use nominal interest rates -- you have to take out inflation.)

In my opinion, we should not expect the average individual of the future to be wealthier than at present, especially if global warming continues.

Another problem has to do with how much damage is expected from global warming and how fast it is expected to happen. So far, some events like the rise in the oceans and arctic thaw are happening much faster than expected.

Frankly, it's not obvious to me that an aggressive program to combat global warming wouldn't have positive economic impacts in the near term instead of negative ones. The things we need to do, using more solar and wind, using less coal and oil, and reducing deforestation, should make most people better off in the near term, even leaving aside the effects on the atmosphere. But such changes would also cut business returns for the owners of our current energy infrastructure, and so they will fight it every step of the way. We are going to use less oil no matter what is decided, simply because the cost of finding more continues to rise.

There's a pretty good article on assessing the economic value, or lack of it, in combating global warming in the latest Scientific American...

Read that article. Wasn't very impressed either.

Another problem has to do with how much damage is expected from global warming and how fast it is expected to happen. So far, some events like the rise in the oceans and arctic thaw are happening much faster than expected.

It's not clear to me that there will be any net damage at all. there will certainly be some places where things are different. However, humans - and almost everything else that lives, even penguins - do better in warm climates.

Frankly, it's not obvious to me that an aggressive program to combat global warming wouldn't have positive economic impacts in the near term instead of negative ones.

Well, I agree that's possible. However, it's not clear that an aggressive program to combat global warming won't have negative environmental impacts. The recent proposal - also in Scientific American - to cover a good chunk of the American Southwest with solar cells is a possible case in point.

The things we need to do, using more solar and wind, using less coal and oil, and reducing deforestation, should make most people better off in the near term, even leaving aside the effects on the atmosphere.

One problem with solar and wind is that the places where you get a lot of sun and wind are also usually places of considerable natural beauty - and also often quite far from where the power will be used. The recent conflict over placing wind generators off Cape Cod is a case in point. I happen to like watching wind turbines work; however, seeing hundreds of them across the landscape of central Wyoming might turn some people off. (If you think about it, a wind turbine is more of less the equivalent of a dam for air, and a solar array is one for sunlight).

But such changes would also cut business returns for the owners of our current energy infrastructure, and so they will fight it every step of the way.

I'm dubious. Environmental regulations have usually profitted large corporations, because they have the staff and resources to deal with them. Solar cells and wind turbines are not garage hobbyist items. They are also maintenance intensive, especially wind turbines (I once read a description of a small wind turbine as a useful way to provide modest amounts of power to an isolated building, and a large wind turbine as a useful way to do destructive testing of structural materials). And no matter what you do for power, you still need a way to get it from where it's being generated to where people want to use it, which will not bother energy transmission firms at all.

We are going to use less oil no matter what is decided, simply because the cost of finding more continues to rise.

I don't find much to disagree with there. You can certainly make oil out of oil shale or coal liquification, and the US has more than enough of those, but the costs would be about what we're paying now. While the era of oil may not be over, the era of cheap oil certainly is.

Slightly contradictory there: You claim any given species has no particular right to continue existing if it can't adapt to human lifestyle, cuddly species not being exempt from this; and then go on to say you don't like wind/solar because it might destroy some "natural" beauty.

"any net damage at all. there will certainly be some places where things are different. However, humans - and almost everything else that lives, even penguins - do better in warm climates.
"
no net damage???? read the IPCC report on impacts. Increased sea levels, flooding, and more intense weather systems have a very very expensive and real physical damage to people's livlihoods.

We aren't talking about a warmer climate. We're talking about a changed climate. Many areas of the world may become colder, and/or dryer. ie less habitable to humans and to penguins.

Yes you could describe all these changes as mere differences. But adapting to living in a different environment to the one you are used to costs. It costs money, time and effort.

"it's not clear that an aggressive program to combat global warming won't have negative environmental impacts"

No-one ever said it would be easy. Like all real world problems and solutions it is a matter or trading off competing concerns. If an environment is going ot be radically altered by changing weather than maybe it's worthwhile to radically alter some of it pre-emptively to reduce the alteration of the rest of it: but how much are we prepared to pay for doing so.

#20 and hidden costs. Of course the status quo has many hidden costs too - climate change being only one of them. A true cradle to grave comparative analysis of all inputs and outputs is extremely difficult for any process and I've not seen one.

Slightly contradictory there: You claim any given species has no particular right to continue existing if it can't adapt to human lifestyle, cuddly species not being exempt from this; and then go on to say you don't like wind/solar because it might destroy some "natural" beauty.

As an individual I find many places beautiful, but I don't wish to force my taste on others - or have them force theirs on me. I did not explain myself clearly enough; I don't have much objection to building power plants, whether they be solar or wind or coal or nuclear, but I fear some of the proponents of "renewable" energy have not really thought through all the implications.

As far as species go, the whole concept is largely a human one, rather than a "natural" one - since we're interested in touchstones, see Systematics and the Origin of Species from the Viewpoint of a Zoologist. Again, I personally have no objection to "rescuing" species that humans find attractive - I would certainly contribute to the "rescue" of many vertebrate species; but I can't get to worked up over the fact that every time I make a loaf of bread billions of yeast are baked alive.

"any net damage at all. there will certainly be some places where things are different. However, humans - and almost everything else that lives, even penguins - do better in warm climates.
"
no net damage???? read the IPCC report on impacts. Increased sea levels, flooding, and more intense weather systems have a very very expensive and real physical damage to people's livlihoods.

The climate has changed considerably more than the worst projections of the IPCC in the past million years or so. Just as a minor example, there are Pleistocene wave-cut beaches in Maine many feet above current sea level (see Atlantic Coast Beaches: A Guide to Ripples, Dunes, and Other Natural Features of the Seashore.

The supposed increased intensity of weather systems has been pretty thoroughly debunked and is an example of the armwaving approach that I find annoying. Weather intensity depends on temperature difference, not on absolute temperature; if the entire planet gets uniformly warmer weather intensity can't change. (For example, there's certainly no evidence of decreased weather intensity during the Pleistocene, or the "Little Ice Age" (The Little Ice Age: How Climate Made History, 1300-1850), and I haven't seen anyone claim increased weather intensity during the Medieval Climate Optimum. Weather patterns might change, so that parts of the world my get different weather from what their used to; but again, deciding that the weather that happened during a particular human lifetime is somehow "normal" is the height of anthropocentric arrogance.

We aren't talking about a warmer climate. We're talking about a changed climate. Many areas of the world may become colder, and/or dryer. ie less habitable to humans and to penguins.

And more habitable to other things.

Yes you could describe all these changes as mere differences. But adapting to living in a different environment to the one you are used to costs. It costs money, time and effort.

Think of the seasonal difference in climate in a city like (for example) Chicago. The average temperature in a Chicago July is 55 degrees F warmer than the average January temperature. But Chicagoans are somehow not going to be able to adapt to an average July and an average January 1 degree warmer?

"it's not clear that an aggressive program to combat global warming won't have negative environmental impacts"

No-one ever said it would be easy. Like all real world problems and solutions it is a matter or trading off competing concerns. If an environment is going ot be radically altered by changing weather than maybe it's worthwhile to radically alter some of it pre-emptively to reduce the alteration of the rest of it: but how much are we prepared to pay for doing so.

#20 and hidden costs. Of course the status quo has many hidden costs too - climate change being only one of them. A true cradle to grave comparative analysis of all inputs and outputs is extremely difficult for any process and I've not seen one.

So we're willing to change the world economy - something which nobody claims to understand - to combat a presumed climate change - something that a lot of people claim to understand. I may be cynical, but it seems that the same people who want dramatic changes in human lifestyle are often vehemently opposed to changes elsewhere - genetic engineering or nuclear power are examples. (This may be unfair - I have no idea of your personal opinions on these matters).

"We aren't talking about a warmer climate. We're talking about a changed climate. Many areas of the world may become colder, and/or dryer. ie less habitable to humans and to penguins.

And more habitable to other things." Also "The climate has changed considerably more than the worst projections of the IPCC in the past million years or so. Just as a minor example, there are Pleistocene wave-cut beaches in Maine many feet above current sea level "

Those being non-human!

I completely accept your premise that humans are unlikely to destroy or in anyway significantly alter Earth. However we are beginning to badly fowel our own nest, and currently lack another to move to. Human society and culture is set to the current climate. If we want to continue living as close as we can to today's standards and even improve them we need to take some steps to minimise the changes in climate.

"Think of the seasonal difference in climate in a city like (for example) Chicago. The average temperature in a Chicago July is 55 degrees F warmer than the average January temperature. But Chicagoans are somehow not going to be able to adapt to an average July and an average January 1 degree warmer? "

You are (deliberately?) confusing climate and weather. The difference is huge. Of course 1-3 degree increase in temperature on its own wouldn't be too troublesome: there would be shifts in plants growing and haesting cycles, pests and predators may get out of sync, but we could probably cope. However this temperature change triggers other changes in rainfall and cloud patterns, which trigger yet further changes.

You are (deliberately?) confusing climate and weather.

I don't think so. Daily variation is weather; seasonal variation is climate. The July and January temperatures in Chicago (again, just as an example) are multiple-year averages - which would be climate - not what happens on particular days in particular Januarys and Julys - which would be weather. Today in Denver it's a little cool for the 11th of June, but I don't presume that it means global warming is mythical.

Human society and culture is set to the current climate. If we want to continue living as close as we can to today's standards and even improve them we need to take some steps to minimise the changes in climate.

I suppose it depends on what you mean by "current"; in my opinion there isn't really a "current" climate; it's been surprisingly variable even before times where there was significant human impact (although human impact may go back further than is usually thought). I recently read - just as an example, I'm not pretending these are definitive works on the subject - both The Ice-Age History of Southwestern National Parks and The Prehistory Of Colorado and Adjacent Areas. Both of these document fairly extensive variation in local ecosystems since the end of the Pleistocene - insofar as that can be done with the archaeological and paleontological records. Not only were there considerable variations in things like the location of the tree line (bouncing up and down by hundereds of feet) but also repeated instances of "novel" ecosystems - combinations of insects (the author of the first book is a paleoentomologist) and plant associations (from pollen in pack-rat nests) that not only don't occur today, but hadn't occured before or since. Similarly, I was suprised to find from the second book that the bison population of Colorado apparently entirely disappeared during archaeological time, and then reappeared before European contact. Climatic change? Just a culture change (the natives stopped using bison for some unknown reason)? Something else?

The general trend in human history seems to be that things improve with warming; the case of Greenland was mentioned in #7 above. Of course, there could be a historical and ethnic bias here - when things were good for Norse settlers in Greenland during the Medieval Climate Optimum, they may have been terrible for Mbuti in the Congo basin, but we happen to have historical and archaeological records from Greenland but not the Congo. In this context, despite talk about "global climate change", there isn't a meaningful "global climate"; people and other organisms find a way to live in climates as different as central Siberia and the central Sahara. Right now I'm in Koppen BSk - steppe (well, actually I'm in an air-conditioned office, but at least outside it's BSk). A hour's drive away I can be in Dfc. (Hmm. I wonder if that might be why North Americans are less enthusiastic about "combatting" climate change than - say - Northern Europeans; we already have quite a bit of climate variability). I also note that historically - and especially in the last few decades - Americans and Canadians have been rather enthusiastic about warmer climates - you see a lot more people moving to Miami and Phoenix than to Minot and Moose Jaw.

28> "The general trend in human history seems to be that things improve with warming" -- I don't buy that. Things got better in Greenland to be sure. They are getting better in Greenland right now. For your typical Narsaq resident, global warming is just fine, at least if his/her house is not too close to the shoreline.

However, the Medieval Climate Optimum was a time of drought in a number of places. This drought may have ended the Chaco Canyon culture, the Maya empire, and so on, with subsequent population collapse. "Population collapse" is a gruesome process -- lots of people starving to death. Global warming is likely to have exactly that result, as food producing areas are submerged beneath rising oceans, or become desertified, or are subjected to severe flooding. Maybe we will make up for this destruction of farmland by all the bananas we'll be able to grow in Canada, the oranges of Siberia, and the amber waves of grain on Greenland and Baffin Island, but I suspect things won't balance out quite that happily.

29> However, the Medieval Climate Optimum was a time of drought in a number of places. This drought may have ended the Chaco Canyon culture, the Maya empire, and so on, with subsequent population collapse.

Granted for the Anasazi. I'm not sure about the Maya. The relationship between temperature and precipitation seems too complicated for the climate modelers; the Medieval Climate Optimum was a time of increased preciptation in Europe followed by drought in the Little Ice Age.

Maybe we will make up for this destruction of farmland by all the bananas we'll be able to grow in Canada, the oranges of Siberia, and the amber waves of grain on Greenland and Baffin Island, but I suspect things won't balance out quite that happily.

Well, let's see. In order to be able to grow bananas (temp range 10-40 C, 100mm rain/month) in, say, Winnipeg (Koppen Dfb, July avg 20 C, Jan avg -16 C, total annual precip 514 mm), we would have to get the January average temperature to rise 26 C, and more than double annual precipitation. I believe the worst case IPCC prediction is what, 4.5 degrees for 2050?

As I posted way back in #3, I do think there is probably on ongoing change in climate - archaeological and paleontological records indicate that climate has been constantly changing; why should it stop now? Whether human activities have a significant influence on that change - maybe. Will the extreme predictions of disaster will come true? No way; we've seen much larger temperature fluctuations in the archaelogical and paleontological record and nothing even remotely resembling these scenarios happened - biological and human populations rearranged a little, same species went extinct, some thrived - same as always.

I wonder sometimes if any of the climate theorists and modelers ever read any history or archaeology or paleontology. What I see is not just crying "Wolf!", it's crying "HUGE WOLVES!!! GREAT SLAVERING PACKS OF MANEATERS!!! WITH ACID FOR BLOOD AND ARMED WITH DEATH RAYS!!!"

I feel the real worst case scenario for anthropological global climate change is that when the dire predictions don't come true people will lose confidence in all scientific judgement (although perhaps I shouldn't be too pessimistic; it hasn't slowed Paul Ehrlich down any).

You've convinced me that I won't be able to grow bananas in Winnipeg in my lifetime. I guess I shouldn't have bought shares in Canadian Banana Ventures from that salesman last week.

And here I was thinking that AGW activists didn't have a sense of humor. I'm ashamed of my stereotyping. :)

On the question of whether humans are causing climate change, there seem to be 2 hurdles:

1. Do you have trouble explaining the Greenhouse Effect to people? Do skeptics not believe that our atmosphere is responsible for the Earth being warmer than the dead of space?

If people understand that our atmosphere is responsible for our habitable temperatures here on Earth, it is no stretch for them to see that the amount of those gases is important. Right?

2. Now, the only hurdle is making them understand what those gases are and how many new tons of those gases humans put into the atmosphere every day.

The climate is EXTREMELY complicated. But understanding that we are constantly putting more greenhouse gases into the Earth's atmosphere is not rocket science.

1. Do you have trouble explaining the Greenhouse Effect to people? Do skeptics not believe that our atmosphere is responsible for the Earth being warmer than the dead of space?

The temperature of a black body in equilibrium with solar radiation at the Earth's orbital distance is about 280K. The average surface temperature of the Earth varies depending on who's measuring, but a middle-of-the-road value is around 287K. The average surface temperature was 7-10 C cooler - i.e., more or less the same average temperature it would have if there was no atmosphere at all and it was in equilibrium with solar radiation - as recently as the Late Pleistocene (and maybe even the Younger Dryas). The Earth was perfectly habitable then, as long as you stayed off the continental ice sheets.

If people understand that our atmosphere is responsible for our habitable temperatures here on Earth, it is no stretch for them to see that the amount of those gases is important.

The atmosphere is certainly responsible for the planet being habitable, but not because of the "greenhouse effect". As demonstrated above, if there were no greenhouse gases at all the planet would be a little cooler but still in the habitable range. (Now, if there were no atmosphere at all, that of course would be different. It doesn't do you much good to have an average temperature of 280K if one side of the planet is 200 degrees cooler and the other is 200 degrees warmer because there's no atmosphere to allow heat transfer).

Now, the only hurdle is making them understand what those gases are and how many new tons of those gases humans put into the atmosphere every day.

The current atmosphere has the lowest concentration of carbon dioxide since the Permian, when it got down to about 350 ppm. In the Cambrian, it was up around 7000 ppm. I don't think trilobites had a lot of fossil fuel emissions.

I'm not opposed to the idea that the global climate is changing, or that humans might be having an effect on it. From a geological perspective, however, that effect is small. Similarly, from a geological perspective it's anthropocentric hubris to imagine that the current condition of the planet is somehow the "correct" one that has to be "preserved" just because we happen to be living in it. If it's thought that we can change climate accidentally, I can't wait to see what happens when we deliberately try to "fix" it.

The point is that it is the "correct" climate for humans and if we would like to continue living we should "preserve" it. Certainly the temperature of the earth has varied throughout history, but you might notice that the makeup of complex life also changed dramatically.

It confuses me that people doubt our ability to change the temperature - we know it has been changed by different ecological patterns in the past, and we humans have completely reformed the surface and ecology of the earth in the past few hundred years. Of course the temperature will be changing, how could it not? The real question is how much and what effect that will have on humanity, and as these are all projections they will never have perfect scientific accuracy. Rather small fluctuations have major impacts, especially on rainfall patterns, in many models. How long can we wait for more information? Cutting back on emissions that we know have an impact on temperature has essentially no down-side; we know fuels with a negative impact on the environment are limited anyways, and we know that the planet is fine at lower emissions levels. So why gamble?

The point is that it is the "correct" climate for humans and if we would like to continue living we should "preserve" it. Certainly the temperature of the earth has varied throughout history, but you might notice that the makeup of complex life also changed dramatically.

Humans evolved in a climate a little warmer than it is now, and went through a whole lot of time when it was a whole lot colder than it is now. Even in that trivially short period of time called "recorded history" there were substantial climate changes that obviously had nothing to do with human activities. Sure, global ecosystems have changed since life evolved, but there's no particular evidence that any of those changes had anything to do with climate (I'll grant that some, possibly many, of them did, but that's pretty had to demonstrate just using the fossil record). Please forgive me if this category happens to include you, but it sometimes seems that when people want to "preserve" the planet they mean they want to "preserve" it the way it is if you happen to be a middle class white Western suburbanite.

It confuses me that people doubt our ability to change the temperature - we know it has been changed by different ecological patterns in the past,...

Well, it was certainly changed by having a good part of the Northern Hemisphere covered with ice in the Pleistocene, and having an asteroid the size of a county run into it simultaneously with the eruption of the Deccan flood basalts at the end of the Cretaceous, and packing all the continents together in one big chunk at the start of the Triassic. Those activities are still somewhat beyond human capabilities.

...Cutting back on emissions that we know have an impact on temperature has essentially no down-side...

I believe that's the central point in our disagreement. I'm afraid there very much will be a down side. Right now, in order to significantly reduce carbon dioxide emissions you also have to significantly reduce energy consumption as a whole, and reducing energy consumption will almost certainly have an effect on the global economy. To put it another way, I happen to believe that right now we just happen to have the "correct" economy for humans - well, OK, correct for middle class white Western suburbanites - and I am loath to mess around with it until we can accurately predict what the consequences will be. I note that the same modelers who are convinced that they can correctly predict dire effects on the global climate don't seem to be able to come remotely close to being able to predict dire problems with the global economy. If the economy is a simpler system than the climate, they ought to be able to do that; and if it's a more complicated system, why are we going to mess around with something we don't understand (the economy) to fix something we claim that we do (the climate).

A whole bunch of things that we've done in the past, just in this relatively restricted time and place on the planet, were claimed to be good for "the environment" or "nature" or "the ecology" or "conservation" or whatever it happened to be called at the time. These included suppressing forest fires, building dams, killing predators, channelizing rivers and so on, and they were done on the most sincere advice of the best minds of the times. I have no confidence at all that similar measures proposed to "prevent global warming" won't actually end up making things worse.

>33 zdufran: As Seknakt points out in 34, the deniers usually say that the chemical composition of the atmosphere, esp. CO2, does not effect our surface temperature. This is definitely a minority position.

>34 setnahkt: "The temperature of a black body in equilibrium with solar radiation at the Earth's orbital distance is about 280K. The average surface temperature of the Earth varies depending on who's measuring, but a middle-of-the-road value is around 287K."

Ah, but the Earth is definitely *not* a black body. It is highly reflective in fact. Which is why we'd be cold as can be if it weren't for the atmosphere. And the chemical makeup of the atmosphere is very important in how warm we are.

We can cut CO2 emissions sharply without big cuts in lifestyle. There are quite a number of proposals on how this can be done relatively cheaply. However, I don't see any way we can sustain higher temperatures without enormous impact on our lifestyle. Cutting CO2 emissions is the cheaper alternative.

Besides which even if the CO2 issue was not present, we still don't have enough oil to sustain the growth of the current economy. We may have slightly more leeway, to extract every last possible drop of carbon, but not significantly. Either way the carbon based economy of the whole world has to change.

Regarding previous unrelated issues, being wrong in the past is no guidance whatsoever that a different 'they' are wrong this time. And there has never been anything even close the IPCC looking at the issues.

I'm mixing responses to two different posts here.

>37 jmcgarve: As Seknakt points out in 34, the deniers usually say that the chemical composition of the atmosphere, esp. CO2, does not effect our surface temperature. This is definitely a minority position.

Oh, it does all right. Just to make that clear:

Setnahkt says "The composition of the Earth's atmosphere affects the Earth's surface temperature. Just not as much as a lot of people think."

For the next comment I'm quoting jmcgarve quoting me; I hope that isn't confusing:

>37 jmcgarve:>34 "The temperature of a black body in equilibrium with solar radiation at the Earth's orbital distance is about 280K. The average surface temperature of the Earth varies depending on who's measuring, but a middle-of-the-road value is around 287K."

Ah, but the Earth is definitely *not* a black body. It is highly reflective in fact. Which is why we'd be cold as can be if it weren't for the atmosphere. And the chemical makeup of the atmosphere is very important in how warm we are.

Yes, but it would be a lot more like a black body - a lot less reflective - if it didn't have an atmosphere; no water, no clouds, no icecaps, no plants. So since we know what a black body temperature would be, we can get a rough estimate of what an Earth-without-an-atmosphere would be. So, then, what do you think the average temperature of an Earth with an atmosphere but without greenhouse gases would be (can't quite do that, I admit - still need water vapor, which is a considerable more potent greenhouse gas than carbon dioxide). Something I have to keep coming back to is that the current atmospheric carbon dixoide content is the lowest it's been since the Carboniferous (and the preindustrial concentration was the lowest it's been since the Cambrian - 600 My or so) but the average Earth surface temperature is not the coldest it's ever been. If atmospheric carbon dioxide is so intimately related to global average temperature, why is that?

>37 jmcgarve: We can cut CO2 emissions sharply without big cuts in lifestyle. There are quite a number of proposals on how this can be done relatively cheaply.

Well, people certainly keep saying that.

>37 jmcgarve: However, I don't see any way we can sustain higher temperatures without enormous impact on our lifestyle. Cutting CO2 emissions is the cheaper alternative.

Again, remember that the average seasonal temperature difference in a place like (for example) Chicago is 55 degrees. Having grown up and gone to college in Chicago, I can assure you I was able to survive from January to July without all that dramatic changes in my life style. Maybe not Winnipeg. :)

>38 reading_fox: Besides which even if the CO2 issue was not present, we still don't have enough oil to sustain the growth of the current economy. We may have slightly more leeway, to extract every last possible drop of carbon, but not significantly. Either way the carbon based economy of the whole world has to change.

No argument there. Just like I get in fights - well, lets call them discussions - with AGW people over carbon dioxide, I get in fights with "oil cornucopians" over oil. I suspect that someday people will be amazed that we once burned oil rather than using for lubrication and as a chemical feedstock. There are some possibilties, of course; there's more oil in US oil shale deposits that there is in all the oil ever extracted on the planet plus all the known reserves, but it won't be cheap to get it out. With oil prices remaining high regardless of what we do, economics will force carbon emissions to drop.

>38 reading_fox: Regarding previous unrelated issues, being wrong in the past is no guidance whatsoever that a different 'they' are wrong this time. And there has never been anything even close the IPCC looking at the issues.

I can't really say much in response to that; we really have no way of knowing yet. I see the problem coming not from the IPCC - which, right, wrong, or inconclusive is resonably restrained - but from various other parties that interpret IPCC reports far beyond reasonable; the kind that predict megahurricanes and drowning polar bears and shutdown of the North Atlantic circulation.

So you accept the IPCC's conclusions?

I certainly agree that much popular media reporting leaves a great deal to be desired. On this and many other scientific (and non) issues.

40>So you accept the IPCC's conclusions?

Way back when this started - post 3>, I think - I noted that I certainly agree that global temperatures are increasing (which distances me from a lot of warming skeptics) and that human activity may - even probably - has something to do with that (which distances me from some more skeptics) but that both the degree of human contribution, the supposed deleterious effects of continued warming, the degree to which the human contribution can be controlled, and the supposedly risk-free results of instituting those controls are all overstated, with the degree of overstating ranging from slight to ridiculous depending on what particular things you are talking about.

Short answer if necessary for future reference: Setnahkt agrees with some but not all of the IPCCs conclusions. See post 41> for details.

> 34. Similarly, from a geological perspective it's anthropocentric hubris to imagine that the current condition of the planet is somehow the "correct" one that has to be "preserved" just because we happen to be living in it.

Hmmm.. of course, there is no "correct", but I think the point here is that, although we need a "geological perspective" on this, we should not equate dramatic global trends on the scale of a human lifespan with change occurring over geological time. Yes, the Earth has been both cooler and warmer in the past with atmospheres very different from today's, but do we really want to live in a radically different environment within a few decades? Indeed, can we effectively manage that rate of change? A similar argument - and one I am regularly challenged with - is the fact that the millions of species went extinct over geological time, which therefore means that we should not be concerned about the current wave of extinctions.

> 42. ...but do we really want to live in a radically different environment within a few decades? Indeed, can we effectively manage that rate of change?

Steven Mithen, in After the Ice, notes that at the beginning of the the Younger Dryas (around 12kya) the global temperature dropped around 5 degrees F in a very short time - probably around a decade and certainly much less than a human lifespan. Similarly, at the end of the YD the temperature rose around 7 degrees F in a decade. This is much greater than anything the IPCC predicts for the next century, much less the next decade, and people made it through OK. The change was also a lot greater than the change from the Medieval Climate Optimum to the Little Ice Age; I note that it's always been called the Medieval Climate Optimum, not the Medieval Climate Disaster.

A similar argument - and one I am regularly challenged with - is the fact that the millions of species went extinct over geological time, which therefore means that we should not be concerned about the current wave of extinctions.

It's not clear that there is a "current wave of extinctions"; i.e., that extinctions are happening at a rate different from preindustrial or prehuman times. Yes, some photogenic species have gone extinct, clearly due to human activites, but what would the extinction rate be without humans? There's not enough evidence to tell. I see a lot of armwaving about thousands of species disappearing but these are all dubious estimates based on dubious number for the number of species extant and equally dubious numbers about the number lost due to climate change or habitat fragmentation. The confusion is exacerbated by the US Endagered Species Act's protection of "subspecies" and "populations", neither of which has a currently accepted biological meaning.

Setnahkt, I am having trouble understanding what you mean by "people made it through OK" with respect to the climate changes of the Younger Dryas. While the archeological record is not definitive, the consensus seemed to be that the human population dropped as the Younger Dryas arrived. People could no longer find the food on which they depended, and a large percentage of them starved. The human species survived, true -- but this is a very low standard for "people made it through ok".

Also, at the start of the Younger Dryas, most people were hunter-gatherers. Now we depend on intensive agriculture. A 3 to 4 degree climate change now would dramatically affect agriculture, cutting yields in many places. Greenland and Siberia may become more fertile, so I suppose we could adapt to the change by mass migration -- but many folks will not make it, and the process will be extremely expensive, cutting living standards more, IMHO, than a transition to renewable fuels.

Already some the inhabitants of countries like Maldives and Tuvalu know that they must relocate, as rising seas will soon make these countries uninhabitable. But they are finding that other countries do not want to let them in. As global warming happens, "people will make it through ok" in that the species will survive. But for many people, global warming will be the end.

Hello setnahkt! I take your points. I'm not sure this is the right place for this discussion as it probably has little to do with books (or climate change!) - unless we can swing it around... but just two observations:-

> Yes, some photogenic species have gone extinct, clearly due to human activites

The ONLY species we have been able to objectively monitor in this respect are vertebrates and, particularly, birds. They are large, showy, highly vocal, easy to count and therefore photogenic too. So it is no coincidence that we notice the photogenic species disappearing, but not little brown jobs.

> It's not clear that there is a "current wave of extinctions"; i.e., that extinctions are happening at a rate different from preindustrial or prehuman times.

I don't think that's true. If you look at recent (last 200 years say) extinctions in the groups that we do have data for (e.g. birds), you will find that almost all of them are human-induced. I cannot think of a single case (though there may be some) of an extinction having occurred that is not related to human activity in some way. Furthermore, very solid bird census data from many industrialised (European) countries show marked population crashes in the last few decades in almost all species, typically in the order of 50% or more. From the little data we have, the situation appears to similar in Latin America, Africa and Asia. So we are defintely looking at an extinction event in birds. Is this replicated in other taxa? I don't know for certain, but I suspect it is. Amphibians are one group that has many people worried, but mammals are not faring all that well either.

I think that, given the data we now have to hand, it would be safer to assume that an extinction event is imminent and to try to do something about it, than to try to hope that the data is not accurate.

I wish I could link this to a book or two. There must be a good objective book on this. Perhaps we should start an "Extinction" thread with that information?

44> Setnahkt, I am having trouble understanding what you mean by "people made it through OK" with respect to the climate changes of the Younger Dryas...The human species survived, true -- but this is a very low standard for "people made it through ok".

Well, that is more or less what I mean - the human species survived. We're pretty adaptable. We are not, however, immune to fluctuations in the environment any more than any other species is.

A 3 to 4 degree climate change now would dramatically affect agriculture, cutting yields in many places. Greenland and Siberia may become more fertile, so I suppose we could adapt to the change by mass migration...

The average annual temperature in Butte, Montana is 39 F. In Cheyenne, Wyoming it's 46 F, a 7 degree difference. In Denver, Colorado it's 51 F, 12 degrees from Butte and 5 degrees from Cheyenne. In Albuquerque, New Mexico, it's 57 F, 18 degrees from Butte, 11 degrees from Cheyenne, and 6 degrees from Denver. In Phoenix, Arizona, it's 73 F, 34 degrees from Butte, 27 from Cheyenne, 22 from Denver, and 16 from Albuquerque. I've been to all those places - people live and grow crops in all of them. I live in Denver; I can drive to a place where the average annual temperature is 3-4 degrees warmer or colder in an afternoon. Agricultural staples are already adapted to a much wider range than that - the extreme northern limit will expand and the southern limit will contract, but the centers of production will not change. I note that a lot of the initiatives for extreme measures to counter global warming come from Europe, and I don't think Europeans quite get the amount of climatic variation that already exists in places with continental climates like North America or Russia.

Already some the inhabitants of countries like Maldives and Tuvalu know that they must relocate, as rising seas will soon make these countries uninhabitable.

Well, it may sound callous but if you live in a place where the maximum elevation is 3 feet above sea level sooner or later random fluctuations are going to get you anyway. In the US, people have learned some hard lessons about inhabiting low-lying coastal areas and river flood plains. You can't get insurance if you want to build a house there; I'm not sure the Maldives aren't an example of this on a international scale. If sea level were stabilized right now, sooner or later an Indian Ocean cyclone or tsunami would wipe out the Maldives. Evacuating the islands makes sense regardless of what happens to current sea level.

45> ... The ONLY species we have been able to objectively monitor in this respect are vertebrates and, particularly, birds.

Well, that's part of the problem We don't know what the natural extinction rate is. Birds, in particular, are particular hard to fossilize - we can't say that the same number of bird species didn't go extinct between -18500 and -18000 as went extinct between 1500 and 2000.

> It's not clear that there is a "current wave of extinctions"; i.e., that extinctions are happening at a rate different from preindustrial or prehuman times.

I don't think that's true. If you look at recent (last 200 years say) extinctions in the groups that we do have data for (e.g. birds), you will find that almost all of them are human-induced.

I agree that many recent enxtinctions are human-induced. However, that doesn't mean the overall rate is different from prehuman times.

Furthermore, very solid bird census data from many industrialised (European) countries show marked population crashes in the last few decades in almost all species, typically in the order of 50% or more.

And is this different from population fluctuations that happened in preindustrial or prehuman times? Because the fossil record of birds is so scanty, and even with an abundant fossil record it's hard to tell what population numbers were. Even if extinctions are occuring due to human activites, it's not clear that it has anything to do with global warming; habitat destruction (or more correctly, habitat modification) is a much stronger candidate.

I think that, given the data we now have to hand, it would be safer to assume that an extinction event is imminent and to try to do something about it...

Perhaps. I'm all for species preservation. I would love it if there were still mammoths and ground sloths and American lions and dire wolves, or even passenger pigeons and Carolina parakeets. I donate money to environmental groups that push for habitat conservation. However, I object to treating the preservation of every species that currently exists as a quasi-religious duty requiring governmental coercion. Many people like the opportunity to travel to areas of "natural" beauty, or just to know that they exist even if they don't travel there; I'm one of them. However, many people also like strip malls and single family-homes. It is politically correct to praise the first group and decry the second; I, sometimes reluctantly, want to defend them.

Hello setnahkt!

> I agree that many recent enxtinctions are human-induced. However, that doesn't mean the overall rate is different from prehuman times.

No, we don't know for certain what the natural extinction rate is. What we do know is that, of documented extinctions in groups we have all the data for, almost all are caused by humans. So we do know that we are causing most extinctions now in these groups, whether or not the overall rate has changed (and the only way for the overall rate to remain unchanged would be for other factors to have decreased their effects). The fact that we are the major cause of extintion AS FAR AS WE KNOW, surely, must be a cause for concern. We clearly do not have enough time and resources to have the luxury of waiting until we know precisely how many species there are how each of them is faring. Rather, the sample we do have should be taken to be representative until we know different.

> And is this different from population fluctuations that happened in preindustrial or prehuman times? Because the fossil record of birds is so scanty, and even with an abundant fossil record it's hard to tell what population numbers were.

Yes, it is different, in the sense that a) we are a relatively new factor, and b) the changes we cause are overwhelmingly in the direction of reducing diversity. So if we want to inhabit a diverse world and to enjoy all that that implies, we need to consider what to do.

> Even if extinctions are occuring due to human activites, it's not clear that it has anything to do with global warming; habitat destruction (or more correctly, habitat modification) is a much stronger candidate.

I'm sorry for confusing this issue with the example of species extinction. I brought it up as the arguments over the two issues - especially those that invoke geological time - are remarkably similar and, to my mind, misleading.

> I object to treating the preservation of every species that currently exists as a quasi-religious duty requiring governmental coercion.

Hmmm... I don't think the scientific arguments do or should have any similarity to religion. Religion characteristically relies on faith, whereas the arguments for conserving biological diversity have nothing to do with faith and everything to do with reason and science (although, of course, there may be other value judgments and cultural factors involved). On the contrary, religion - especially the concept that "man has been set above nature" - is frequently used to justify activities which cause significant environmental degradation. Having said that, some of the current "species conservation" initiatives in the US and parts of Europe do seem to have scant scientific basis, especially those which aim to conserve widespread species which happen to be on the edge of their range (and therefore rare and vulnerable) in, say, the US or UK. So I am all for an objective assessment of the problems, but I don't think we should wait for all the evidence to be in before we start to act.

>48 chrisharpe: ...What we do know is that, of documented extinctions in groups we have all the data for, almost all are caused by humans.

...Yes, it is different, in the sense that a) we are a relatively new factor, and

I have to say that you have argued your points well and that I am in general agreement with both of these statements.

...b) the changes we cause are overwhelmingly in the direction of reducing diversity. So if we want to inhabit a diverse world and to enjoy all that that implies, we need to consider what to do.

I'm not sure I agree with that one, though. "Diversity" is one of those things where everybody knows what it means but nobody can offer useful definitions. "Diversity" is generally conceded to be some sort of measure of the number of species that exist and the way they are partitioned. The problem is that the operational definition of species is vague to nonexistant. There is a "biological species definition", pioneered by Ernst Mayr, but this is a philosphical concept rather than an actual way species can be distinguished in the field. The US Endangered Species Act complicates matters by allowing endangered "subspecies" and "populations", neither of which has been a valid biological concept for decades. In actual practice, a species and even more a subspecies or population depends on a taxonomist's opinion rather than any rigorously applicable standard (and, of course, given the way evolution works that's probably the best definition you can hope for. Thus the key argument for reduction in diversity depends on arbitrary opinions.

Clearly human activities has elimated some habitats or reduced others below viability. At the same time, we haven't changed the area of the planet, we've just rearranged things. As a result, some species prosper while others decline. Things as diverse as camels, horses and hamsters only exist because of people; all are extinct in the wild. Human habitat modification has benefited some species; the North American robin (different from the European robin) is probably the most abundant bird on the continent; it was rare before European contact but it just loves suburban lawns. I have been priveleged to see a peregrine falcon kill and eat a pigeon in a railyard in the middle of downtown Denver - the pigeon colony was living in the decorative tower of a motel and the falcon was presumably one of those that has taken up nesting on skyscraper ledges, neither of which was a habitat available in 1492 (in fact, it was a Europena pigeon so that wasn't available either). There are species - not photogenic ones, admittedly, unless your a microscopist - that have appeared solely because of human activities - bacteria that eat nylon and fungi that eat pentachlorophenol.

I'm sorry for confusing this issue with the example of species extinction. I brought it up as the arguments over the two issues - especially those that invoke geological time - are remarkably similar and, to my mind, misleading.

Well, that's fine; the issue of global warming blends into other environmental topics - popultion size, fossil fuel use, and so on. There hadn't been much discussion in the global warming thread for a while so it's just a well to take up something related.

As far as geological time goes, being (technically) a geologist my opinions may be a little skewed. However, it's all a matter of scale; for bacteria, a week is geological time; for bristlecone pines, a millenium isn't. This is, of course, a personal opinion, but I've found lack of comprehension of geological - or even archaeological - time and global distances are considerable handicaps to understanding the way natural systems work.

> I object to treating the preservation of every species that currently exists as a quasi-religious duty requiring governmental coercion.

Hmmm... I don't think the scientific arguments do or should have any similarity to religion.

In theory, they don't. In practice, I find that a lot of the "environmentalists" I deal with treat scientific theories as if they were revealed dogma. I find it especially ironic that people on both sides of the religion-scientific divide tends to treat the planet as if it were created in 4004 BCE on October 23rd at 09:30. Many environmentalists - at least, as near as I can tell from their writings - tend to think of species the same way that creationists do: as fixed and immutable "kinds" that have always been here and that will never change, and of habitats and climate as eternally constant, despite abundant scientific evidence to the contrary.

Religion characteristically relies on faith, whereas the arguments for conserving biological diversity have nothing to do with faith and everything to do with reason and science...

That's the theory, but lay people (and evens sometimes scientists) tend to assume that scientific concepts a lot more solidity than the really deserve. I already mentioned the haziness of such things as "species" and "diversity"; I could probably cite a bunch more - "ecosystem" and "community" (in the ecological sense) come to mind. Thus we have things like the Endangered Species Act, which is full of good intentions but is interpreted by people who have no real idea what either "species" or "endangered" means. Similarly, I'm always dealing with the Clean Air Act and Clean Water Act as interpreted by regulators who have a completely unrealistic idea of what as putatively simply a concept as "clean" means. (I concede they're fairly competent in identifying "air" and "water").

On the contrary, religion - especially the concept that "man has been set above nature" - is frequently used to justify activities which cause significant environmental degradation.

Not being religious, I fully agree that man has not been "set above" nature. However, I don't think "man" is obligated to fix all the problem "man" sees with nature either. The thing that concerns me is that somewhere along the line the "man" that's supposed to "preserve" nature seems to come to mean "people whose lifestyle I disapprove of" and who need to be presuaded to agree with my opinions of the "correct" lifestyle with the aid of regulations, court orders, and eventually coercion.

Having said that, some of the current "species conservation" initiatives in the US and parts of Europe do seem to have scant scientific basis, especially those which aim to conserve widespread species which happen to be on the edge of their range (and therefore rare and vulnerable) in, say, the US or UK.

No argument there. To further complicate matters, even what constitutes a species range is up for debate. Where do you set the line on what the "natural" range of a particular species is? As an example, there's a definite record of a magnificent frigate bird (Fregata magnificens) from Gunnison, Colorodo, which is about as likely as finding one in the London Underground. Similarly, there are definite physical remains of jaguars in Colorado. Should this state be counted as within the "natural" range of either species? On the flip side, there's a strong archaeological arguments that the bison, that iconic animal of the West, was once (in Precolumbian times) totally extinct in the state, and pollen evidence that Kansas supported a extensive spruce forest during Clovis time. You can make a pretty strong argument that the supposedly "natural" environment of (for example) the North American Great Plains is very unstable. After all, it's only been 10K years or so - not much in evolutionary time - since mammoths, mastodons, cheetahs, camels, llamas, lions, ground sloths, short faced bears, stag moose and a wide variety of other mammals and birds (and presumably smaller things) went extinct. We shouldn't be surprised at all if the Great Plains environmental is still rearranging itself, with additional species going extinct and others moving in from elsewhere.

So I am all for an objective assessment of the problems, but I don't think we should wait for all the evidence to be in before we start to act.

In general, I agree; as said, I donate money to environmental organizations engaged in habitat preservation. However, that assumes we know what actions to take and that those actions will actually accomplish the results we desire (not to mention the results that are "natural"). As an example, the South Platte River flows past my office. For an urban river, it's pretty rich in wildlife; the water is usually quite clear (thanks to strenuous efforts to reduce pollution) and I've seen painted turtles, snapping turtles, muskrats, kingfishers, double-crested cormorants, American egrets, black crowned night herons and (once) a sandhill crane all within a few hundred feet of the 31st Street bridge.

However, the early Colorado settlers always described the South Platte as "too thick to drink but too thin to plow". I expect that buffalo herds and Native Americans probably didn't pay much attention to avoiding churning up the water and increasing sediment load. As a result, it's quite likely that perfectly well-intentioned environmental rules aimed at reducing anthropogenic sediment in the river actually made it too clean; most of the endangered fish species in Colorado are adapted to live in turbid water. (Of course, low sediment loads probably aren't the only reason they're endangered, but I bet they contribute).

Perhaps I'm overly pessimistic. After all, one of my points is that the natural world is a lot more adaptable to changed conditions than people seem to think it is, and that can be taken both ways; just as "nature" has stood up fairly well under previous human efforts to "dominate" it, so it will likely also stand up fairly well to attempts to "fix" it. I'm more worried about the way humans stand up; past efforts to "fix" human society for one reason or another don't exactly have a laudable record.

Climatologist Heidi Cullen, PhD, released a 2011 paperback edition of her book oriented toward the general public on the subject of climate change:

The Weather of the Future: heat waves, extreme storms, and other scenes from a climate-changed planet

Are We in the Middle of a Sixth Mass Extinction?
Anne Gibbons. Science Now: Up to the Minute News from Science. 2011-03-02
http://news.sciencemag.org/2011/03/are-we-middle-sixth-mass-extinction

"Earth's creatures are on the brink of a sixth mass extinction, comparable to the one that wiped out the dinosaurs. That's the conclusion of a new study, which calculates that three-quarters of today's animal species could vanish within 300 years. "This is really gloom-and-doom stuff," says the study's lead author, paleobiologist Anthony Barnosky of the University of California, Berkeley. "But the good news is we haven't come so far down the road that it's inevitable.""

"Species naturally come and go over long periods of time. But what sets a mass extinction apart is that three-quarters of all species vanish quickly. Earth has already endured five mass extinctions, including the asteroid that wiped out dinosaurs and other creatures 65 million years ago. Conservationists have warned for years that we are in the midst of a sixth, human-caused extinction, with species from frogs to birds to tigers threatened by climate change, disease, loss of habitat, and competition for resources with nonnative species. But how does this new mass extinction compare with the other five?"

"Barnosky and colleagues took on this challenge by looking to the past. First, they calculated the rate at which mammals, which are well represented in the fossil record, died off in the past 65 million years, finding an average extinction rate of less than two species per million years. But in the past 500 years, a minimum of 80 of 5570 species of mammals have gone extinct, according to biologists' conservative estimates—an extinction rate that is actually above documented rates for past mass extinctions, says Barnosky. All of this means that we're at the beginning of a mass extinction that will play out over hundreds or thousands of years, his team concludes online today in Nature. ..."

Barnosky, AD, et al. 2011. Has the Earth’s sixth mass extinction already arrived? Nature 471, 51–57 (03 March 2011) http://www.nature.com/nature/journal/v471/n7336/full/nature09678.html

Abstract: Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.

Figure 1: Relationship between extinction rates and the time interval over which the rates were calculated, for mammals.
Figure 2: Extinction magnitudes of IUCN-assessed taxa 6 in comparison to the 75% mass-extinction benchmark.
Figure 3: Extinction rate versus extinction magnitude.

****************************************

Thomas, CD. et al. 2004. Extinction risk from climate change. Nature 427, 145-148 (8 January 2004). http://www.nature.com/nature/journal/v427/n6970/full/nature02121.html

Abstract. Climate change over the past ~30 years has produced numerous shifts in the distributions and abundances of species1, 2 and has been implicated in one species-level extinction3. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15–37% of species in our sample of regions and taxa will be ‘committed to extinction’. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction (~18%) than mid-range (~24%) and maximum-change (~35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.

Table 2. Estimated eventual extinction based on habitat loss.
http://www.nature.com/nature/journal/v427/n6970/fig_tab/nature02121_T2.html#figu...

#43 Steven Mithen, in After the Ice, notes that at the beginning of the the Younger Dryas (around 12kya) the global temperature dropped around 5 degrees F in a very short time - probably around a decade and certainly much less than a human lifespan. Similarly, at the end of the YD the temperature rose around 7 degrees F in a decade. This is much greater than anything the IPCC predicts for the next century, much less the next decade, and people made it through OK.

OK? Maybe people survived as a species, but no doubt some populations (Clovis?) were decimated if not exterminated, and cultures changed (to scavenging) as large mammals went extinct...

"... Dartmouth University geochemist Mukul Sharma along with his colleagues opposes the previous theories that explain the rise in the meltwater from the North American ice sheet by providing conclusive evidence stating that the dramatic shift in climate occurred due to an object from space, either a comet or an asteroid."

"The event took place some 12,900 years ago" (in s Quebec, they think) "and triggered a colder and dryer climate across the world. The impact of the space object caused all big animals like camels, giant ground sloths and saber toothed cats to vanish in North America and also a group of human hunters referred to as Clovis people stopped hunting and turned into gatherers eating roots, smaller animals and berries."

"The Younger Dryas cooling is a very intriguing event that impacted human history in a profound manner," Sharma, a professor in the Department of Earth Sciences and one of the authors of a new paper said in a statement. "Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture."..."

http://www.scienceworldreport.com/articles/9220/20130903/meteor-impact-quebec-12...

>52 margd: OK? Maybe people survived as a species, but no doubt some populations (Clovis?) were decimated if not exterminated, and cultures changed (to scavenging) as large mammals went extinct...

Are you suggesting the North American large mammal fauna went extinct in response to the Younger Dryas? The Younger Dryas was a quick bounce; a short return to cooler conditions more typical of Pleistocene glaciation, followed by warming back to where things were after the end of the Pleistocene. The North American large mammal fauna had made it through both the glaciation and the post-glacial warming without any problems apparent from the fossil record. The main difference was there were now humans in North America, but there are various arguments against the Clovis Overkill hypothesis as well.

And the Younger Dryas was a world-wide event; there's no evidence of mass extinctions elsewhere. In the book I cited (After The Ice), it's noted that the archaeological record shows changes in human cultural adaptations, but there's no evidence that populations were "decimated".

The supposed Younger Dryas impact event keeps popping up in popular literature, but it's been pretty thoroughly debunked on the scientific level. See

http://www.agu.org/books/gm/v198/2012GM001209/2012GM001209.shtml

and

http://www.pnas.org/content/107/37/16043.abstract

for example.

I just don't know where to begin--your info and interpretations are so--but re absence of diamonds (20120), "... In this (2013) study the researchers focused on spherules, droplets of solidified molten rock released by the comet as it crashed into the Earth's atmosphere. The researcher obtained the spherules from boundary layers of Younger Dryas at various sites in Pennsylvania and New Jersey deposited at the beginning of the period. They then compared the geochemistry and mineralogy profiles of these spherules to the rocks found in southern Quebec and discovered that both the samples matched..."

Imagine the violence of an impact that would send bits of Quebec to PA and NJ!

Clovis people's big-game hunting culture was replaced by something more akin to gatherers (scavengers?), and they are not thought to be significantly represented in modern Native American's DNA. Sounds like decimation to me--and not something I'd like to see repeated, if by smart moves on our part we can save people dependent on drinking water fed by glaciers or people whose countries may be drowned.

And now, I'm off to vacation near the apparent impact site of comet. Amazing, the signs of historical violence in that part of the world: long parallel scrapes in bedrock (like inverse railway trails, from icebergs?), E-W oriented reefs on bottom of L Ontario (ice dam break on the Niagara R?), L Ontario's Charity Shoal (meteor strike), etc.

>54 margd: I just don't know where to begin--your info and interpretations are so--

You're just going to leave me hanging like that, not know whether my "info and interpretations are so -". So cogent? So idiotic? Ah well, enjoy your vacation with best wishes from me.

The link you provided does offer new support for the Younger Dryas impact theory; I'll have to wait and see how it plays out in the scientific literature.

No reaction to today's IPCC report...? ;-)

Haven't read the IPCC report; probably won't get around to it for a while. As noted in earlier posts, I think the concept of anthropogenic climate change is pretty well established; it just that I think it's not as big a problem as it's made out to be and that many of the proposed "solutions" will cause more harm than good.

I was only trying to stir things up setnahkt. It does look as if we are getting to much higher degrees of confidence now. The effects have been striking in some of the places I know well - e.g. tropical Andes and UK. Let us know what you think when you've read it!

Still haven't read the full report - it's 2200 pages long - but I read a couple of review articles in Science. The conclusions are not very different from earlier versions. The upper limit for carbon dioxide induced warming has dropped somewhat, as has the maximum sea level rise. The report notes the difficulties inherent in the term "equilibrium global warming", which is the expected temperature after everything has settled down.

F Estrada, P Perron, & B Martínez-López. 2013. Statistically derived contributions of diverse human influences to twentieth-century temperature changes. Nature Geoscience. Published online 10 November 2013. http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1999.html

Abstract

The warming of the climate system is unequivocal as evidenced by an increase in global temperatures by 0.8 °C over the past century. However, the attribution of the observed warming to human activities remains less clear, particularly because of the apparent slow-down in warming since the late 1990s. Here we analyse radiative forcing and temperature time series with state-of-the-art statistical methods to address this question without climate model simulations. We show that long-term trends in total radiative forcing and temperatures have largely been determined by atmospheric greenhouse gas concentrations, and modulated by other radiative factors. We identify a pronounced increase in the growth rates of both temperatures and radiative forcing around 1960, which marks the onset of sustained global warming. Our analyses also reveal a contribution of human interventions to two periods when global warming slowed down. Our statistical analysis suggests that the reduction in the emissions of ozone-depleting substances under the Montreal Protocol, as well as a reduction in methane emissions, contributed to the lower rate of warming since the 1990s. Furthermore, we identify a contribution from the two world wars and the Great Depression to the documented cooling in the mid-twentieth century, through lower carbon dioxide emissions. We conclude that reductions in greenhouse gas emissions are effective in slowing the rate of warming in the short term.

K Marvel and C Bonfils. 2013. Identifying external influences on global precipitation. Proceedings of the National Academy of Sciences. Published online before print November 11, 2013. http://www.pnas.org/content/early/2013/11/05/1314382110 (Accessed Nov 13, 2013)

Abstract: Changes in global (ocean and land) precipitation are among the most important and least well-understood consequences of climate change. Increasing greenhouse gas concentrations are thought to affect the zonal-mean distribution of precipitation through two basic mechanisms. First, increasing temperatures will lead to an intensification of the hydrological cycle (“thermodynamic” changes). Second, changes in atmospheric circulation patterns will lead to poleward displacement of the storm tracks and subtropical dry zones and to a widening of the tropical belt (“dynamic” changes). We demonstrate that both these changes are occurring simultaneously in global precipitation, that this behavior cannot be explained by internal variability alone, and that external influences are responsible for the observed precipitation changes. Whereas existing model experiments are not of sufficient length to differentiate between natural and anthropogenic forcing terms at the 95% confidence level, we present evidence that the observed trends result from human activities.