Warmer, no doubt. But how? (Photo Hermio82.)
The climate may be less sensitive to carbon dioxide than is commonly believed. And then the temperature rise in this century will be less than expected.
Such a surprising result led the analysis of the last ice age. But this data is only one climate model. While they can not be recreated with the help of others, experts do not give up the skeptical grimace.
It has long been known: the more greenhouse gases in the atmosphere, the more heat is trapped and the greater the temperature increases. But how much? The most authoritative estimate says that if the amount of carbon dioxide in the atmosphere will double, the planet will warm by 3? C. This is the climate sensitivity.
Do not forget that this is only an estimate. The report of the Intergovernmental Panel on Climate Change (IPCC) in 2007 stated that the climate sensitivity can be from 2 to 4,5? C. That's the uncertainty. She tried to remove Andreas Shmittner at Oregon State University (USA) and his colleagues.
Researchers have focused on the last glacial maximum (about 20 thousand years ago). Using published data, they made detailed global map of the surface temperature. It was found that on average, the planet was then at 2,2? C colder. Ice cores, leave no doubt that this was accompanied lower levels of carbon dioxide in the atmosphere.
Mr. Shmittner enter data about what was then the atmospheric concentration of greenhouse gases in the computer model and received an unexpected value of climate sensitivity: 2,4? C.
If it really is, in this century warming is not as bad as the IPCC warned. Experts said that if we will continue to lean on fossil fuels, by 2100 the average global temperature will rise by about 4? C, compared to the average of 1980-1999.
Commentator Gavin Schmidt of the Institute for Space Studies. Goddard NASA (USA) did not consider the results credible. It indicates that the model, the researchers took advantage of the services which underestimates the cooling of the Antarctic and mid-latitudes. That is the estimate obtained for the global average temperature during the last glacial maximum overstated. In fact, it was cold. Accordingly, the temperature has since grown much stronger, and hence climate sensitivity should be higher.
Mr. Shmittner agrees that his hands were only preliminary data. Even 2,4? C — a very strong warming.
The study is published in the journal Science.
Prepared according to NewScientist.