Sources Of Global Temperature Variations

Sources Of Global Temperature Variations

. A reconstruction of the Sunís brightness over the past 400 years indicates that the global temperature fluctuations from 1600 to 1800 were mainly due to variations in solar activity. Cooling by haze from volcanoes played a role during the next 100 years. The global temperature increases after the mid-1970ís, are mainly caused by heat-trapping greenhouse gases emitted by industrial economies. Here the decadally averaged values of Northern Hemisphere summer surface temperatures (scale at left) are compared with the reconstructed solar total irradiance (symbols, scale at right). The dark solid line is paleoclimate temperature data, primarily tree rings, and the gray dashed line is instrumental temperature data. (Courtesy of Judith Lean.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University