It’s clear that the world was warmer during medieval times. Marked on the map are study after study (all peer-reviewed) from all around the world with results of temperatures from the medieval time compared to today. These use ice cores, stalagmites, sediments, and isotopes. They agree with 6,144 boreholes around the world which found that temperatures were about 0.5°C warmer world wide.
***UPDATED: For more details on what boreholes show see this detailed post which updates this one. While other proxies give us information on the relative temperature and the timing, boreholes suggest the warming was global. Climate models don’t explain past global temperature swings. They don’t understand all the factors that drive the climate. The fact that the IPCC ignored this graph, which at the time agreed with most proxies, tells us the IPCC is not driven by science but by politics. The way the interpretation of borehole results have swung wildly reflects how politicized science has become.
*UPDATE: This graph [...]
