Unusual Heat

Unusual Heat

. This reconstruction of the hemisphere temperature record suggests that the Northern Hemisphere has been warmer in the 20th century than in any other century of the last thousand years. The sharp upward jump in the temperature during the last 100 years was recorded by thermometers at and near the Earth’s surface. Earlier fluctuations were reconstructed from “proxy” evidence of climatic change contained in tree rings, lake and ocean sediments, and ancient ice and coral reefs. The farther back in time the reconstruction is carried, the larger the range of possible error, denoted by the light shaded regions. (Courtesy of Michael E. Mann.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University