English: From the cited public-domain source (US Environmental Protection Agency (US EPA), 2012): "These maps show temperatures across the world in the 1880s (left) and the 1980s (right), as compared to average temperatures from 1951 to 1980. This difference from average is called an anomaly. The map on the left shows that it was colder in the 1880's in most places. The map on the right shows it was warmer in the 1980s in most places. Earth's average surface temperature has increased almost 1.5°F during the 20th century. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.3°F-0.4°F per decade."