New calculations show that sensitivity of Earth’s climate to changes in the greenhouse gas carbon dioxide (CO2) has been consistent for the last 420 million years, according to an article in Nature by geologists at Yale and Wesleyan Universities.
The authors Dana L. Royer, Robert A. Berner and Jeffrey Park used
500 data points in the geological records as “proxy data” and evaluated them in the context of the CO2 cycling models of co-author Robert Berner,
“Our results are consistent with estimates from shorter-term records, and indicate that climate sensitivity was almost certainly greater than 1.5, but less than 5.5 degrees Celsius over this period,” said Park.
This result is actually very interesting (though not unexpected) because we keep hearing from so called skeptics that the CO2 concentration has been much higher at times in the past – which is correct. This now shows that that there have also been higher temperatures, the contribution of CO2 to climate is confirmed to be real and the magnitude of the sensitivity is in line with climate models. New is that they used data from hundreds of millions of years ago. So far this had only been done for a few hunded thousand years, so for the last ice ages.
PS: the picture has been extracted from the pdf using gimp.