But this research does argue for a different path to global warming in the past, which means that estimates of the planet's sensitivity to various levels of CO2 based on measurements from the Ice Age may be flawed, Stott argues. "We are a long way from refining the climate sensitivity to a doubling of CO2 [that] is going to take place in the next 100 years," he notes.
Stott plans to investigate how ocean warming led to a CO2 rise in the past, research that could also have implications for present climate change. But one impact of the new finding is already clear, Stott says: "a regional change in climate can propagate into a global response."
With Arctic ice retreating more and more as local summers heat up, exposing ever more cold northern waters to warming sunshine—along with a host of other regional changes—it remains to be seen exactly how sensitive global climate really is. "We just don't know very well," Stott acknowledges, "how the climate itself, which is much more than temperature, is going to behave."
*Article updated on 9/28/07.