Recently a german taxi driver asked me if climate hasn’t been changing in the past with similar warm periods as the one we have now. After getting back home to Corvallis, Oregon, I read a letter to the editor of our local newspaper claiming that it was much warmer than today during the medieval warm period. What has the most recent science to say? As the figure below shows global average temperatures haven’t been as high as today for about 5,000 years. Going back even further in time it was warmer or similar as today during the last interglacial (Eemian) period about 120,000 years ago. These warm periods had natural causes (humans didn’t play a role) but the current human-made warming is much faster than past natural changes.
Both the Marcott et al. and the PAGES 2k reconstructions, which are independent from each other, agree that global climate has cooled slowly during the past several thousands years. The so called medieval warm period was probably just a regional phenomenon in Europe, the North Atlantic and North America, but it did not affect global temperatures and it was not warmer than today. In fact, it was about 0.3 deg C cooler than the last 30 years.