May 2, 2021
Tim May has an interesting article on temperature reconstruction from Greenland ice cores up on WUWT. The article is interesting and reasonably understandable for those of us who casually follow climate science. There are two bits of the article I found particularly interesting, charting of the ice core testing results with average and historical markers and the opening paragraph of the conclusion. I encourage you to read the entire article.
The use of temperature proxies to determine surface air temperatures prior to the instrument era is very important. It is the only way to determine natural long-term natural climate cycles. Currently, in the instrument record, we can see shorter cycles like the PDO, AMO, and ENSO. When these are incorporated into models, we see that half or more of recent warming is likely natural, belying the IPCC idea that “most” of recent warming is man-made. Yet, these shorter cycles are clearly not the only cycles. When we look at longer temperature reconstructions, we see 40,000, 80,000 or 120,000-year glacial periods interrupted by brief 10,000 to 18,000-year interglacial periods. These longer periods will probably only be fully understood with more accurate reconstructions. Intermediate ~1,500-year cycles, called “Bond events,” the 2,450-year Bray, and the 1,000-year Eddy cycles have also been identified and need to be better understood.