JoNova

A science presenter, writer, speaker & former TV host; author of The Skeptic's Handbook (over 200,000 copies distributed & available in 15 languages).


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Medieval Warm Period found in 120 proxies. Plus Roman era was similar to early 20th Century.

Two major proxy studies, larger than ever, were released in April and June 2012. They show that the Medieval Warm Period (MWP) existed, and was similar to current temperatures. These comprehensive studies suggest current temperatures are not unusual, and that itself is not all that surprising — I’ve mentioned before how there are hundreds of proxy studies showing it was as warm or warmer back then. (CO2science has been documenting them.) But these studies are worth a mention because they are so large.

Climate models cannot explain what caused the warming 1000 years ago, nor the cooling  300 years ago, so they can’t rule out the same factors aren’t changing the climate today (though they claim they can). If climate models can’t explain the past, they can’t predict the future.

The last 12 Centuries

Ljungqvist used 120 proxy records — nearly 3 times as many proxies as previous studies and conclude: “during the 9th to 11th centuries there was widespread NH warmth comparable in both geographic extent and level to that of the 20th century”. Their proxies included ice-cores, pollen, marine sediments, lake sediments, tree-rings, speleothems and historical documentary data.

Ljungqvistet al 2012 Fig. 4. Mean time-series of centennial [...]