Richard Harris’ NPR story this week exploring how global temperatures stayed pretty constant over the last decade even as greenhouse gas concentrations increased reminded me of another important piece of research overlooked during last month’s global climate negotiations in Copenhagen:
Yale University researchers studying past warming episodes that didn’t get any help from the Industrial Revolution say the climate may be more sensitive to carbon dioxide than we previously understood.
The study by Yale’s Climate and Energy Institute found that about 4.5 million years ago, when the concentration of CO2 in the atmosphere was roughly what it is today, global temperatures were 2 to 3 degrees Centigrade higher. This is a pretty big deal, recall, because we’re talking about global average temps. The extremes are higher and the effects are more far-reaching than, say, a simple bump in the mercury on a summer day of 2 to 3 degrees might suggest.
The big message is sobering. It means that even the climate simulations scientists have constructed through modeling could be underestimating the amount of warming we’re going to see given what we’ve already pumped into the atmosphere.
Here’s how lead author Mark Pagani, Yale associate professor of geology and geophysics, put it:
This work and other ancient climate reconstructions reveal that Earth’s climate is more sensitive to atmospheric carbon dioxide than is discussed in policy circles. Since there is no indication that the future will behave differently than the past, we should expect a couple of degrees of continued warming even if we held CO2 concentrations at the current level.
And holding CO2 at current levels, as we’ve discussed, just ain’t gwyne happen.
And, folks, before some of my faithful correspondents start pointing out that the Earth’s climate has always changed without our help… puh-leeze. That doesn’t mean what we’re doing can’t affect it. If you’re having trouble with that concept, go to the local university and sign up for a logic course, OK?
— Robert McClure