lpetrich
Contributor
Paleoclimate: The End of the Holocene « RealClimate
At the beginning of the Holocene, around year -10,000, the average temperature was the reference temperature - 0.2 C. It went up to +0.2 C at year - 8000, roughly stayed that way until -3500, then started to decline, getting to -0.35 C by the 19th cy. Its recent increase has been *very* fast, *much* faster than anything previous, and greater than the early-Holocene peak.
At the beginning of the Holocene, around year -10,000, the average temperature was the reference temperature - 0.2 C. It went up to +0.2 C at year - 8000, roughly stayed that way until -3500, then started to decline, getting to -0.35 C by the 19th cy. Its recent increase has been *very* fast, *much* faster than anything previous, and greater than the early-Holocene peak.
I think for three reasons it is extremely likely that there was not such a rapid warming before:
1. There are a number of high-resolution proxy data series over the Holocene, none of which suggest that there was a previous warming spike as strong as in the 20th Century. Had there been such a global warming before, it would very likely have registered clearly in some of these data series, even if it didn’t show up in the averaged Marcott curve.
2. Grant Foster performed the test and hid some “20th C style” heating spikes in earlier parts of the proxy data to see whether they are revealed by the method of Marcott et al – the answer is a resounding yes, they would show up (albeit attenuated) in the averaged curve, see his article if you are interested in the details. [Update 18 Sept: one of our readers has confirmed this conclusion with a different method (Fourier filtering). Thanks!]
3. Such heating must have a physical basis, and it would have to have quickly disappeared again (would it have lasted, it would be even more evident in the proxy data). There is no evidence in the forcing data that such a climate forcing could have suddenly appeared and disappeared, and I cannot imagine what could have been the mechanism. (A CO2-induced warming would persist until the CO2 concentration decays again over thousands of years – and of course we have good data on the concentration of CO2 and other greenhouse gases for the whole Holocene.)