Climate sensitivity to CO2 more limited than extreme projections, says new study

A new study suggests that the rate of global warming from doubling of atmospheric carbon dioxide may be less than the direst estimates of some previous studies – and, in fact, may be less severe than projected by the Intergovernmental Panel on Climate Change report in 2007.

Authors of the study, which was funded by the National Science Foundation's Paleoclimate Programme and published online last week in the journal Science, say that global warming is real and that increases in atmospheric CO2 will have multiple serious impacts.

However, the most Draconian projections of temperature increases from the doubling of CO2 are unlikely.

''Many previous climate sensitivity studies have looked at the past only from 1850 through today, and not fully integrated paleoclimate date, especially on a global scale,'' said Andreas Schmittner, an Oregon State University researcher and lead author on the Science article. ''When you reconstruct sea and land surface temperatures from the peak of the last Ice Age 21,000 years ago – which is referred to as the Last Glacial Maximum – and compare it with climate model simulations of that period, you get a much different picture.

''If these paleoclimatic constraints apply to the future, as predicted by our model, the results imply less probability of extreme climatic change than previously thought,'' Schmittner added.

Scientists have struggled for years trying to quantify ''climate sensitivity'' – which is how the Earth will respond to projected increases of atmospheric carbon dioxide.