After I heard a claim that our nation’s top climate scientist "once warned of Ice Age" — I (and no doubt many others) emailed Hansen and said he should reply to the rapidly morphing and spreading myth. He has here (PDF).

I will reprint what he has to say below (you can also go to that link for an interesting commentary, "Please talk to your grandfather"):

In 1976, with four colleagues, I wrote my first paper on climate (Science, 194, 685-690, 1976). Based on the suggestion of Yuk Yung, one of the co-authors, we examined, for the first time, whether several human-made trace gases might have an important greenhouse effect (until then, only carbon dioxide and chlorofluorocarbons had been considered). We found that methane and nitrous oxide were likely to be important, though measurements of how these gases might be changing were not yet available. Starting then I became interested, very interested, in the Earth’s climate; indeed, two years later I resigned as Principal Investigator of an experiment on its way to Venus so that I could devote full time to studies of the Earth’s climate.

So it was a bit of a surprise when I began to be inundated a few days ago with reports that I had issued proclamations five years earlier, in 1971, that the Earth was headed into an ice age.

Here is how this swift-boating works. First on 19 September 2007 a Washington Times article by John McCaslin reported that a 9 July 1971 article by Victor Cohn in the Washington Post had been discovered with the title "U.S. Scientist Sees New Ice Age Coming". The scientist, S.I. Rasool, is reported as saying that the world "could be as little as 50 or 60 years away from a disastrous new ice age".

This is an old story: Rasool and (Steve) Schneider published a paper in Science on that day noting that if human-made aerosols (small particles in the air) increased by a factor of four, other things being equal, they could cause massive global cooling. At Steve’s 60th birthday celebration I argued that the Rasool and Schneider paper was a useful scientific paper, an example of hypothesis testing, in the spirit of good science. But what is the news today? Mr. McCaslin reported that Rasool and Hansen were colleagues at NASA and "Mr. Rasool came to his chilling conclusions by resorting in part to a new computer program developed by Mr. Hansen that studied clouds above Venus."

What was that program? It was a ‘Mie scattering’ code I had written to calculate light scattering by spherical particles. Indeed, it was useful for Venus studies, as it helped determine the size and refractive index of the particles in the clouds that veil the surface of Venus. I was glad to let Rasool and Schneider use that program to calculate scattering by aerosols. But Mie scattering functions, although more complex, are like sine and cosine mathematical functions, simply a useful tool for many problems. Allowing this scattering function to be used by other people does not in any way make me responsible for a climate theory.

Yet as this story passes from one swift boater to another it gets juicier and juicier, e.g.:

Global Warming Scientist Once Warned of ‘Ice Age’

By Doug Ware — KUTV.com

[I won’t reprint the whole piece of nonsense here]

It is little wonder that I have been getting nasty e-mails the past several days.

The lesson is: don’t believe everything you read in the press, especially the conservative press.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.