Just in the nick of time to be included in the final draft of the IPCC's Fifth Assessment report, we get...the new Hockey Stick, a paper by Marcott et al.
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
I wonder how those 73 proxies were selected. I wonder which proxies have that extraordinary uptick at the end. And I wonder when the uptick actually started - it looks like 500 years ago to me.
New Scientist covers the paper here. Interestingly they reckon the temperature rise began in the late 19th century.
Then, in the late 19th century, the graph shows temperatures shooting up, driven by humanity's greenhouse gas emissions.
This seems odd, because it is generally understood that carbon dioxide emissions were too small to affect the climate before the 1950s.
It will be interesting to read the paper in full.
Bishop Hill