Global Temperature Changes in the Twentieth Century

Global Temperature Changes in the Twentieth Century

. The annual global-mean temperature near the Earth’s surface is plotted as a temperature difference from the long-term mean value. At more than 0.5 degrees Celsius above the mean, recent global temperatures maintain a warming trend for the past two decades. Natural temperature fluctuations prohibit a clear detection of human-induced warming in the early part of the twentieth century, but human increases of greenhouse gases in the atmosphere may be noticeably contributing to the recent rise in temperatures. The global mean temperature for the period 1880 to 1997 is 13.8 degrees Celsius (56.9 degrees Fahrenheit). [Courtesy of Michael Changery, the National Climatic Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAO).]

Copyright 2010, Professor Kenneth R. Lang, Tufts University