Global average temperature since the last ice age (20,000 BC) up to the not-too distant future (2100) under a middle-of-the-road emission scenario comprising the temperature reconstruction of Shakun, et al. (green – shifted manually by 0.25 degrees), of Marcott, et al. (blue), combined with the instrumental period data from HadCRUT4 (red) and the model average of IPCC projections for the A1B scenario up to 2100 (orange). Graphic: Jos Hagelaars

[Also see Tamino’s analysis: Global Temperature Change — the Big Picture]

By Jos Hagelaars
19 March 2013

The big picture (or as some call it: the Wheelchair): Global average temperature since the last ice age (20,000 BC) up to the not-too distant future (2100) under a middle-of-the-road emission scenario.

Earlier this month an article was published in Science about a temperature reconstruction regarding the past 11,000 years. The lead author is Shaun Marcott from Oregon State University and the second author Jeremy Shakun, who may be familiar from the interesting study that was published last year on the relationship between CO2 and temperature during the last deglaciation. The temperature reconstruction of Marcott is the first one that covers the entire period of the Holocene. Naturally this reconstruction is not  perfect, and some details will probably change in the future. A normal part of the scientific process.

The temperature reconstruction ends mid-20th century, so the rapid temperature rise since 1850 is clearly visible in the graphs presented in their study.

And what do we see? Again something that looks like a hockey stick as in the graph from Mann, et al., 2008. […]

Are the results from Marcott, et al., surprising?

Not really. The well-known graph of Holocene temperature variations on Global Warming Art, which is often encountered on the internet, is actually a comparable image. One could say that Marcott et al managed to scientifically confirm the average thick black line of the Global Warming Art image. [more]

Holocene teperature variations, 12,000 BP - 2004, comprising eight records of local temperature variability on multi-centennial scales throughout the course of the Holocene, and an average of these (thick dark line). The records are plotted with respect to the mid 20th century average temperatures, and the global average temperature in 2004 is indicated. The inset plot compares the most recent two millennium of the average to other high resolution reconstructions of this period. Graphic: Robert Rhodes / Global Warming Art

The two epochs of Marcott

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