By Andy May
In 2000, Richard Alley released an ice core temperature reconstruction for Central Greenland using Oxygen isotope ratios. He describes the technique used here. I used this ice core proxy data in a previous post “Climate and Civilization for the past 4,000 years.” Since Alley’s data stops at 1855, I spliced the Greenland HadCRUT surface temperature data on the end to show the Modern Warm Period. In the previous post I erroneously thought Alley’s reconstruction stopped at 1905, not at 1855, so the plot in the earlier post is shifted 50 years. This problem is corrected in this post. I spent too little time on the splice, since my focus was on the effect of climate on civilization and several commenters rightly objected to the error. These included David Middleton, who offered up a better Central Greenland reconstruction by Kobashi, et al. as an alternative. A little research and I was able to find a 4,000 year reconstruction to 1993 by Kobashi et al.
Kobashi uses Argon and Nitrogen isotopic ratios from air bubbles in the ice to estimate paleo-temperatures. He claims that that his method is more accurate than the Oxygen isotope ratios Alley used. Details of Kobashi’s methods are in his PhD thesis, which can be seen here. His unsmoothed results from 2,000 BC to 1993 are shown in Figure 1.