Guest Post by David Middleton

The Gorebots are all atwitter about this new paper…

Science 8 March 2013: Vol. 339 no. 6124 pp. 1198-1201 DOI: 10.1126/science.1228026 A Reconstruction of Regional and Global Temperature for the Past 11,300 Years Shaun A. Marcott, Jeremy D. Shakun, Peter U. Clark, Alan C. Mix 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. Science

Marcott et al., 2012 is behind a paywall; however the supplementary materials include a link to their proxy data.

This paper appears to be a text book example of creating a Hockey Stick by using a low resolution time series for the handle and a high resolution time series for the blade…

Let’s test one of the 73 proxies.

I picked ODP-1019D, a marine sediment core from just offshore of the California-Oregon border because it has a long time series, is a an annual reconstruction and has a nearby long time series instrumental record (Grants Pass OR).

ODP-1019D has a resolution of 140 years. Grants Pass is annually resolved…

Let’s filter Grants Pass down to the resolution of the Marcott et al. reconstruction…

Grants Pass sure looks very anomalous relative to the rest of the Holocene… Right?

Well, not so fast. ODP1019D only has a 140-yr resolution. The record length at Grants Pass is less than 140 years. So, the entire Grants Pass record would be a single data point in the ODP-1019D record…

While, the most recent ~140 years might be warmer than most of the rest of the Holocene in this particular area, does anyone else notice what I did?

The Grants Pass/ODP-1019D area has been warming at a fairly steady rate for 6,500 years…

I don’t know how many of these proxies I will have time to analyze… Probably not very many. Maybe this could become a WUWT crowd-sourcing project.

Title revised per notes below, 03-11-2013. Mod]

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