Freeman Dyson, professor emeritus at Institute for Advanced Studies, Princeton University, in an email interview:

"Climate change is a real problem, partly caused by human activities, but its importance has been grossly exaggerated.

"It is far less important than other social problems such as poverty, infectious diseases, deforestation, extinction of species on land and in the sea, not to mention war, nuclear weapons and biological weapons.

"We do not know whether the observed climate changes are on balance good or bad for the health of the biosphere. And the effects of atmospheric carbon dioxide as a fertilizer of plant growth are at least as important as its effects on climate."

William Gray, hurricane expert and head of the Tropical Meteorology Project at Colorado State University, in a 2005 interview with Discover magazine:

"I'm not disputing that there has been global warming. There was a lot of global warming in the 1930s and '40s, and then there was a slight global cooling from the middle '40s to the early '70s. And there has been warming since the middle '70s, especially in the last 10 years. But this is natural, due to ocean circulation changes and other factors. It is not human induced.

"Nearly all of my colleagues who have been around 40 or 50 years are skeptical as hell about this whole global-warming thing. But no one asks us. If you don't know anything about how the atmosphere functions, you will of course say, 'Look, greenhouse gases are going up, the globe is warming, they must be related.' Well, just because there are two associations, changing with the same sign, doesn't mean that one is causing the other."

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The continued rapid cooling of the earth since WWII is in accord with the increase in global air pollution associated with industrialization, mechanization, urbanization and exploding population. -- Reid Bryson, "Global Ecology; Readings towards a rational strategy for Man", (1971)

The battle to feed humanity is over. In the 1970s, the world will undergo famines. Hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now. Population control is the only answer -- Paul Ehrlich - The Population Bomb (1968)

I would take even money that England will not exist in the year 2000 -- Paul Ehrlich in (1969)

In ten years all important animal life in the sea will be extinct. Large areas of coastline will have to be evacuated because of the stench of dead fish. -- Paul Ehrlich, Earth Day (1970)

Before 1985, mankind will enter a genuine age of scarcity . . . in which the accessible supplies of many key minerals will be facing depletion -- Paul Ehrlich in (1976)

This [cooling] trend will reduce agricultural productivity for the rest of the century -- Peter Gwynne, Newsweek 1976

There are ominous signs that the earth's weather patterns have begun to change dramatically and that these changes may portend a drastic decline in food production - with serious political implications for just about every nation on earth. The drop in food production could begin quite soon... The evidence in support of these predictions has now begun to accumulate so massively that meteorologist are hard-pressed to keep up with it. -- Newsweek, April 28, (1975)

This cooling has already killed hundreds of thousands of people. If it continues and no strong action is taken, it will cause world famine, world chaos and world war, and this could all come about before the year 2000. -- Lowell Ponte "The Cooling", 1976

If present trends continue, the world will be about four degrees colder for the global mean temperature in 1990, but eleven degrees colder by the year 2000...This is about twice what it would take to put us in an ice age. -- Kenneth E.F. Watt on air pollution and global cooling, Earth Day (1970)

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Yes, it's good of these folks to march today although they are conspicuously absent from where most Americans live, i.e., the suburbs. It is the suburbs, dependent on the auto and truck for their very existence, that need to have the discussion about drastic life style change and the cost of that change. Of course the merry marchers today don't want to discuss the cost, only vague "percents" of how much less carbon we emit. The carbon limitation lobby is suspiciously silent as to what price the average working family must pay to possibly enjoy more stable climate.

Bottom line: limit carbon use without massive adjustments to replace current sources of energy and we face severe recession or depression. Anyone who believes the USA and the West will be more democratic in the face of depression and massive numbers of immigrants competing for limited jobs is insane.

Frankly, the economic price to limit carbon might be necessary if the alternative is the end of Western civilization through weather-related disasters. But is that really the alternative? In any event, nothing is free. There is a price to replace cheap energy and it's about time those who lecture us about environmental responsibility stop the pretense that this will be a pain-free transition.

I think of Fat Al as the primary lecture culprit and those who worship at his wingtips, but even the grassroots marchers, sincere as they are, gloss over the pain carbon reduction will cause billions of people.

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Geez people! How do you protest Mother Nature?

Protest pollution. Protest the war. Protest latex condoms. Protest laws. But to protest climate change is like protesting a hurricane.

First of all, "Climate Change" is too general of a term. But also, we don't control it. At the most, we might be contributing to it in some small way and I'm all for cleaning up the atmosphere just to be on the safe side. But let's get real. We can't change the climate significantly one way or the other like a thermostat controls the temperature in your house.

This movement will definitely have to go down in history as being the epitome of hyperbole.

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It's interesting to see so many skeptical comments here on this subject. Admittedly, lots of things are still up for debate on the matter of climate change, such as what the actual effects would be on the climate in each part of the world, the exact causal relation between various greenhouse gases and observed changes in atmospheric and sea temperature, and whether climate change is as serious an issue as, for example, the ongoing mass-extinction of wild species due to habitat destruction and pollution. But this is always the case in science. Global warming, or more generally "climate change" may not be as well established as, say, the heliocentric model, or plate tectonics, or evolution by natural selection (all of which were controversial at one time), but it's not exactly a "mere" theory, either.

What we see is perhaps 90% of the scientific community in agreement on certain general points (the existence of a warming trend and of some kind of link to human-produced CO2 emissions), and another 10% criticizing these on mutually inconsistent grounds (there's no warming trend; there is but it's not anthropogenic; it is, but it's not harmful, etc. etc.) Some of those 10% are perfectly legitimate scientists with alternative models, and that much debate is part of how science produces good results. Among the 90%, furthermore, there is plenty of debate over methodologies, models, forecasts, and so forth. But what they agree on has to be called the best current understanding of the situation.

They're not guaranteed to be right - science doesn't make guarantees - but the point is that for a layperson (rather than someone with extensive expert knowledge, whose personal judgment can reasonably be said to be based on a realistic appraisal of the evidence) to choose to buy into those minority views is not really a sensible way to evaluate what's basically a scientific issue. Neither should we laypeople "choose sides": what we should do is try to get the best possible sense of what those who know what's going on think (which is hard when we get our information about the world from the Noise Factory). Doing that will always mean accepting things like "confidence levels" and "90%", and "subject to change with new data". One thing we really need is to learn how to act rationally on knowledge that we only have at those levels of certainty.

It's unfortunate to have to rely on experts, especially in an atmosphere (sic!) as anti-intellectual as today's America. But the alternative is this attitude that declares that the truth is basically political - a comfortable position if you have an aversion to uncertainty, but also one that virtually guarantees you'll be persistently wrong about just about everything. For instance, the claim that scientists want to teach evolution, not because the evidence supports it as the best and most plausible theory, but because it discredits (a version of) Christianity, which they (supposedly) hate. Or the notion that someone who proposes that there is or isn't a link between CO2 emissions and climate change is only producing results for personal or political aims (to scare people into funding them - or to please some oil company).

Science doesn't usually work like this, but if anything can make it do so, politicizing the basic research would probably be the thing. Which is a pity, because to do so would be to destroy the scientific establishment in America, and probably the whole world, and it's hard to imagine how to cope with today's world, with its huge population boom and depleting resources, without good science.

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Dear Skeptics--

What don't you understand about...

Average carbon concentrations in the atmosphere being twice as high as they have been in the last 800,000 years, as indicated in the studies of ice cores from Antarctica going back that far?

The polar ice cap melting by 40% since 1970?

Worldwide bleaching of coral reefs?

Worldwide disappearance of glaciers, at unprecedented rates?

The accelerating erosion of the Greenland ice sheet?

The breaking off of huge ice shelves, some the size of Connecticut, in Antarctica?

The accelerating worldwide increase in global carbon concentrations, as measured at the Mauna Loa station in Hawaii, correlating exactly with the explosive worldwide growth of fossil fuel consumption?

The northward spread of tropical diseases?

I could go on and on with extremely well documented data, all pointing to the same conclusion--that climate change today is more rapid than in all recorded history, and that it is directly caused by the dramatic worldwide growth in consumption of hydrocarbon-based fossil fuels since the industrial revolution.

And that, according to the recent consensus report of the Intergovernmental Panel on Climate Change, we may already be past the tipping point, sending global warming into a self-accelerating runaway feedback loop that could, in the next 50 years or less, wipe out more than 1/3 or more species on Earth, turn agricultural areas into deserts, flood coastal cities, and result in the displacement and starvation of billions of human beings.

Deny, deny all you like, but your children and grandchildren, living in a hellish, chaotic, dying world that I would not wish on anyone, will curse you for your denial, and for our collective failure to take action while we still had the chance.

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I still don't get it - the climate shows great variability from historic measures and prehistoric evidence. Scientists don't appear to have "models" that can make predictions with precision . Proof of a scientific theory comes from the ability to predict outcomes. There does not appear to be this kind of proof for global warming.

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What convinces me is the the staggering amount of exhaust we put into the air every day, which has led to twice as much carbon in the atmosphere as has been in the last 800000 years, put there by volcanos and what not, if the figure by a recent poster is correct, That, and the recent scientific consensus. I'm as wary of conspiracy and hidden political agenda as anyone, but I don't see how you can deny it. I'm much more likely to suspect a denialist of a hidden agenda...

We have the potential to create a paradise on earth if we dont mess it up first.
Wresting power from tyrants and serfs to the masses was a big step. Now, in the economic resource-exploitation frenzy/free-for-all that has ensued, monsters have evolved in this vacuum which have convinced masses to entrap themselves in ratwheel systems of consumption and waste secretion, chasing dangling carrots and stepping on the shoulders and faces of each other to "succeed.". The hour is getting late. What is to stop the machine from rushing off a cliff, and crushing what sweet creatures get in its way?

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The theories surrounding Climate change is a complex and incomplete mishmash of astronomical and terrestial observations. Human activity does not explain it completely. As a single Volcanic eruption can spew more hydro carbons into the atmosphere than mankind has produced in the last 100 years. Changes in the intensity of the Sun and the precession cycle of the Earth have effects on the climate to a far greater degree than what man can do. Its all interconnected, with mankind being but 1 link in a complex Earth 'system'. Mother Nature always looks for equilibrium, but that could take 100's of thousands years. We may be in a 'warming' faze, more likely followed by a 'cooling' faze over the next 12,000 years. A link to Earth's temperature change over the last 2 billion years http://www.scotese.com/climate.htm

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That is too many protesters. Did they just get brainwashed by watching an Al Gore movie?

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I read Mr.Schwarzenegger is very worried about climate change so he puts in his two Hummer automobiles only bioethanol.

The American corporations wants their profits, the american people want to keep their lifestyle.
Please donot sell this to Europe as protection of enviroment,
To destroy food to keep your Hummers humming is abhorrent.
If the American government would analyse the results of good public transport(look to France and Schwitzerland)

The good thing: the politicians stopped the WAR in Vietnam because thet saw the marches and were thinking about their jobs.
Hopefully the present marches will be succesfull but be aware about the real problem.

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If we could, we'd split the world with you. We get some, you get some, and somehow we could have a barrier so your pollution wouldn't get into our half. You could continue doing all the things you claim are harmless, and we could clean things up. I predict that in about 5 years, your army would come and invade us and take over, because you'd have poisoned much of your world, you'd be much sicker with diseases like cancer, and you'd see a real beginning of frying your side of the planet. We'd have hopefully slowed down and were enjoying life and relaxation and community, and wouldn't have bothered with an army, so we'd be easy pickings. But then maybe we'd be exiled to your spoiled half, and we'd start cleaning IT up, and it would end up much nicer, and at the same time, of course, you'd be trashing your new half, because you never seem to see what's coming or to learn from your mistake, so here we'd go again. . . .

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