Study Finds Limited Sensitivity of Climate to CO2 - New York Times (blog)

Recalling the perils of single-study syndrome, it's still important to note a new study that appears to go a long way toward narrowing the extent of possible warming projected well into this century from the buildup of carbon dioxide in the atmosphere. Eric Berger of the Houston Chronicle describes the research, published today in Science. The work, led by researchers at Oregon State University, had surfaced earlier but has now survived peer review.

Berger provides useful context from Andrew Dessler, a climate scientist at Texas A&M University, who noted that most people publishing on this question have long seen very low odds of runaway or extreme warming:

My sense is that most scientists consider the very high end of the sensitivity range… to be pretty unlikely (although it cannot be ruled out)…. In other words, I was not terribly worried about runaway climate change before this. After all, we know that the Earth's had much higher CO2 in the past (and the temperature were correspondingly much higher), and the Earth did not turn into Venus.

I'll be doing more on this "sensitive" question soon, drawing in studies taking different approaches. In the meantime, Rachel Nuwer has a post at the Green Blog describing the Science paper. Here's an excerpt and link:

Scientists say the Earth will warm in response to increasing carbon dioxide levels in the atmosphere, but since the 1970s, they have not made much headway in narrowing down exactly how much it will warm.

Typical forecasts say that if humanity doubles the amount of carbon dioxide in the atmosphere before emissions cease, the temperature will most likely rise by about 5.4 degrees Fahrenheit, though the figure could be as low as 3.6 degrees or as high as 8.1 degrees. And scientists have not entirely ruled out far higher numbers.

Now comes a new entry in the effort to specify the value known as "climate sensitivity," and it falls on the low side of the existing estimates. The paper, in the journal Science, calculates that a doubling of carbon dioxide will most likely lead to a warming of 4.1 degrees Fahrenheit, though the number could be as low as 3 degrees or as high as 4.7 degrees.

"Our study shows that very high climate sensitivities are virtually impossible, suggesting that we still have enough time to deal with the problem and reduce carbon emissions, which could avoid the most severe impacts," said Andreas Schmittner, a climate scientist at Oregon State University and the study's lead author. Read the rest.