By Andy May
In previous posts (here and here), I’ve compared historical events to the Alley and Kobashi
GISP2 Central Greenland Temperature reconstructions for the past 4,000 years. Unfortunately, these two reconstructions are very different. Recently Steve McIntyre has suggested a third reconstruction by Bo Vinther. Vinther’s data can be found here. Unfortunately, Vinther is often significantly different from the other two. The Alley data has been smoothed, but the details of the smoothing algorithm are unknown. So the other datasets have been smoothed so they visually have the same resolution as the Alley dataset. Both datasets (Kobashi and Vinther) were first smoothed with a 100 year moving average filter. Then 20 year averages of the smoothed data were taken from the one year Kobashi dataset to match the Vinther 20 year samples. The Alley data is irregularly sampled, but I manually averaged 20 year averages where the data existed. If a gap greater than 20 years was found that sample was skipped (given a null value).
All three reconstructions are shown in Figure 1. There is no reason to prefer one of the three reconstructions over the other two, so I simply averaged them. The average is the blue line. I’m not presenting this average as a new or better reconstruction, it is merely a vehicle for comparing the three reconstructions to one another and to other temperature reconstructions. This is an attempt to display the variability in common temperature reconstructions for the past 2,000 to 4,000 years.
By Prof. Robert M. Carter, James Cook University, Queensland, Australia December 9, 2009
Edited by Andy May [comments in square brackets]
I’ve always liked this essay, written by the late Dr. Bob Carter in 2009. It has been plagued by some formatting issues that detract from the excellent content. This version fixes the formatting problems in the original. In particular the spacing is improved and the “°” symbols in the original had been made into zeros. Besides fixing the formatting issues, adding some graphs, a few hyperlinks and updates in square brackets, I’ve left it as Professor Carter wrote it.
Ten facts about climate change
Climate has always changed, and it always will. The assumption that prior to the industrial revolution the Earth had a “stable” climate is simply wrong. The only sensible thing to do about climate change is to prepare for it.
Accurate temperature measurements made from weather balloons and satellites since the late 1950s show no atmospheric [tropospheric] warming since 1958. In contrast, averaged ground-based thermometers record a warming of about 0.4°C [0.7°C through 2015] over the same time period. Many scientists believe that the thermometer record is biased by the Urban Heat Island effect and other artefacts. [Below are graphs of the UAH satellite troposphere temperature anomaly measurements (which only go back to 1979) , the Hadley CRU surface temperature anomalies and the RATPAC A global weather balloon temperature anomalies averaged to 19 km and to 7 km. The top of the troposphere varies from 7 km at the poles in the winter to 20 km near the equator. Dr. Carter’s point that it depends on where you measure the “average” temperature is well taken.]