April 3, 2012

expert reaction to CO2 and the last ice age

A paper in Nature outlined how important an increase in atmospheric CO2 at the end of the last ice age was to a subsequent rise in global temperatures.

Prof Andrew Watson FRS, Royal Society Research Professor at the University of East Anglia, said:

“This study gives us a detailed picture of the timing of southern versus northern hemisphere temperature rise at the end of the last ice age. These timings are crucial if we want to understand the mechanisms behind climate change. The paper shows that the increase in atmospheric CO2 was very important and drove the global temperature rise, but it also suggests that the initial trigger for the deglaciation was something different – a slight warming and associated slow-down of the Atlantic Ocean circulation. This caused carbon dioxide to start being degassed from the deep oceans, and that in turn drove the global change.

“We are making good progress in working out the complicated cause-and-effect of these past climate changes, and that gives us confidence that we understand the basics of modern climate change as well.”

Prof Mark Maslin, Director of the Environment Institute at University College London, said:

“Jeremy Shakun and colleagues have provided clear evidence that carbon dioxide levels rose before global temperatures at the end of the last ice age. Their painstaking collation of over 80 temperature records from around the world should put paid once and for all to the false claim that the rise in carbon dioxide was a passive response to increased global temperatures.

“The authors also provide a much deeper insight into how the northern and southern hemisphere temperatures responded differently to the end of the last ice age. Their new insights to the climate see-saw caused by heat re-distribution through the deep water system add important knowledge to our understanding of the links between the ice age cycles, atmospheric carbon dioxide feedback and global temperatures.”

‘Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation’ by Jeremy Shakun et al, published in Nature on Wednesday 4 April.