Europe Is Literally Getting Hotter

Guardian UK: Modern European summers are warmest since Roman times, study finds - Average summer temperatures in Europe are about 1.3C hotter than two millennia ago due to manmade climate change, scientists say

Much of the data for the period before 755 comes from analysis of tree rings and density information from three pine tree species in Finland, Austria and Sweden. These trees grow in warm weather but are dormant in the cold, meaning that their rings, density – and the outside temperatures – can only be measured in summer.