NASA scientist warns of runaway global warming

by Michael Le Page, features editor, NewScientist, December 22, 2008

Here's a prediction to take note of: there will be an unambiguous new global temperature record during the first term of the Obama administration.

This prediction comes from leading climate scientist James Hansen of NASA. He made it in response to a question from a member of the audience during a lecture to the American Geophysical Union on 17 December.

The prediction comes at a time when there has been much discussion of average annual global temperatures, and just how hot or cool 2008 really was.

As you will no doubt see from the comments, Hansen is a hate figure for the climate deniers who insist it's getting cooler.

It's a bold and simple prediction, but I'm not sure how helpful it is. Making short-term forecasts is much harder than making long-term ones, and there are some climate researchers who think cyclic changes in the oceans will mask the underlying warming trend for the next five years or so.

What's more, a big volcanic eruption would cause a sharp but temporary dip in temperatures.

If Hansen is right - as he has been before - the deniers will continue to find reasons to persuade themselves it's not true. An ever-popular one is that global warming is all a conspiracy to impose a global government on the world.

If he's wrong, he'll have handed the deniers what might seem like a convincing argument to people who don't know much about the evidence for climate change.

As for the rest of Hansen's lecture, much of it emphasised points he has been making for some time: we should to aim to reduce carbon dioxide levels to 350 parts per million, we cannot afford to built more coal power plants (without carbon capture and storage) and that a carbon tax with a 100% dividend should be introduced.

However, he also made another striking prediction. According to Hansen, human activity is causing greenhouse gas levels to rise so rapidly that his model suggests there is a risk of a runaway greenhouse effect, ultimately resulting in the loss of oceans and of all life on the planet:

"In my opinion, if we burn all the coal, there is a good chance that we will initiate the runaway greenhouse effect. If we also burn the tar sands and tar shale (a.k.a. oil shale), I think it is a dead certainty."

That's a cheerful thought. Let's end instead with a quote from Hansen's new boss:

"Today, more than ever before, science holds the key to our survival as a planet and our security and prosperity as a nation... It's about ensuring that facts and evidence are never twisted or obscured by politics or ideology. It's about listening to what our scientists have to say, even when it's inconvenient - especially when it's inconvenient."

Michael Le Page, features editor

Link to article: http://www.newscientist.com/blogs/shortsharpscience/2008/12/nasa-scientist-warns-of-runawa.html