Update on Antarctic ice and global warming

By James Fallows

The point of the previous item about how scientists think about public policy, which referred to Richard Muller's book Physics for Future Presidents, was that many scientific issues are too complex to be resolved in op-ed columns. Or even Atlantic website posts!

But several people have asked for elaboration of this sentence I quoted from Muller:

"An example of distortion is the melting of the Antarctic ice -- something that actually contradicts the global warming model but is presented as if it verifies them."

What's the logic there? My main answer is, read the book! But to be more responsive, here's the reasoning in a nutshell (my paraphrase, alongside USGS map of Antarctica):

antarctica.jpg

Higher temperatures (ie, "global warming") would mean more evaporation from the oceans. That would mean more clouds, which over Antarctica would mean more snow. (The air over Antarctica would be warmer, but on average still well below freezing.) More snow would mean more Antarctic ice, not less. Yet the Antarctic ice cover is decreasing, not increasing.

"Does the decrease in ice mean that the model is wrong -- that global warming is not taking place?" Muller asks. "No, not at all. It simply shows the inadequacies of the model. Even with global warming, local weather (even for a whole continent) can cause behavior that deviates from the computer calculation. One result is certain: the melting of Antarctica provides no evidence whatsoever in favor of global-warming predictions." He then goes on to discuss other evidence that does support the predictions. To be 100% clear about it: Muller is not at all a "denialist" about climate change. Eg: "Global warming is real. It is very likely caused by humans. By the end of the twenty-first century it will (if caused by humans) grow enough to be disruptive." He is just urging readers and policy makers to be precise about what the evidence shows and doesn't show.

You know where to go for more.

UPDATE: this site, from NASA, allows you to create your own maps showing how much the average temperature in different parts of the world has risen over any interval you choose since 1880. For instance, this map, below, shows surface temperature differences in June, 2009 versus a 1951-1980 average baseline:

GHCN_GISS_1200km_Anom06_2009_2009_1951_1980.jpg


More here from Michael Goodfellow of Free the Memes.

This article available online at:

http://www.theatlantic.com/technology/archive/2009/07/update-on-antarctic-ice-and-global-warming/22044/