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Dimming the Sun

Program Overview


Sun and clouds NOVA investigates the evidence for a little-known phenomenon called global dimming and explores its potential impact on climate worldwide.

The program:

  • relates how the first signs of global dimming came in the 1980s when one scientist—who measured sunlight amounts over Israel in the 1950s—found a 22 percent drop in sunlight 20 years later.

  • reports that scientists were at first skeptical of global dimming, which indicated Earth was getting cooler, because it conflicted with evidence supporting global warming.

  • explains how a decline in pan evaporation rates worldwide, and correlation of the evaporation rates with measured declines in sunlight, further supported the hypothesis of global dimming.

  • describes an experiment measuring the atmosphere over the Maldives that revealed polluted air was causing global dimming.

  • details how polluted air was creating clouds with 10 times more particles than naturally occurring clouds, and that the polluted clouds were both preventing sunlight from getting through and reflecting more sunlight back into space.

  • reports on research indicating that global dimming may have affected normal weather patterns, including altering rainfall patterns that led to a 20-year drought in sub-Saharan Africa.

  • notes how global dimming may be masking the full effects of global warming.

  • presents research showing that vapor trails left behind by high-flying aircraft have a significant impact on daily temperature range.

  • provides estimates for the impacts of global warming and global dimming.

  • predicts what may happen to parts of the world if revised global warming estimates are true.

  • describes a new controversial climate analysis that predicts that temperatures could rise by as much as 10 degrees Celsius by 2100.

  • emphasizes the urgent need to address the causes of global warming.

Taping Rights: Can be used up to one year after the program is taped off the air.

Teacher's Guide
Dimming the Sun