Plenty of studies have shown that the Arctic is warming and that the ice caps are melting, but how does it compare to the past, and how serious is it?
New research shows that average summer temperatures in the Canadian Arctic over the last century are the highest in the last 44,000 years, and perhaps the highest in 120,000 years. (Unprecedented recent warmth in Arctic Canada)
"The key piece here is just how unprecedented the warming of Arctic Canada is," Gifford Miller, a researcher at the University of Colorado, Boulder, said in a joint statement from the school and the publisher of the journal Geophysical Researcher Letters, in which the study by Miller and his colleagues was published online this week. "This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere."Part of the abstract says: (link)
Reconstructed changes in snowline elevation suggest that summers cooled ~2.7°C over the past 5000 years,Courtesy of Dr Tim Ball (link) (written in March 2012 before the above story)
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However, if you are unconvinced by the ice core data, it is supported by physical evidence. Professor Ritchie (University of Toronto) identified and photographed a picea glauca (white spruce) stump on the Tuktoyaktuk Peninsula in tundra some 100km north of the current treeline (Figure 2). Radiocarbon date was 4940 ±140 years Before Present (BP). It was featured in Hubert Lamb’s classic work Climate, Present, Past and Future.Tim says, of the above photo,
(It) is a photo of a White Spruce radiocarbon dated at 5000 years old located 100 km north of the current tree line. Temperatures had to be 2-3°C warmer than at present for this to happen.Warmer 5,000 years ago? So much for Miller et al's "peer-reviewed"unprecedented warmth.
Dr Judith Curry on her blog Climate etc. also wrote:
Miller et al. assume that the Baffin Island melting is attributable to AGW. Maybe it is. In the Chasing Ice post, I noted that the peak glacier discharge from West Greenland occurred in the 1930′s. The Ellesmere ice shelves also saw a melt back earlier in the 20th century circa the 1930′s. The Miller et al. paper does not remark on any evidence of warming in the 1930′s, or the LIA or MWP for that matter, but note only a cooling over the past 5000 years, with marked warming in the past 100 years. The reasoning behind the Miller et al. conclusions is rather complex, with a number of assumptions, I’m not sure what to make of their arguments.
In any event, how representative of the Arctic is their findings from Baffin Island? Well, it doesn’t even seem to be too representative even of Ellesmere Island and West Greenland.After discussion of a somewhat conflicting(peer-reviewed) paper by Opel et al, Dr Curry concludes:
The natural internal variability in the Arctic seems to be an exceedingly complex dance between atmospheric circulations, sea ice, ocean circulations and ice sheet dynamics, on a range of timescales. We have some hints about how all this interacts, but much is unknown. In light of this, simplistic inferences about global warming in the Arctic seem unjustified.