Solar Variation and Earth’s Climate

Everyone agrees the Sun has profound influence on our atmosphere. But what, exactly, are its impacts on climate? Researchers believe that changes in sunspot activity or other solar events may affect Earth in ways that are indirect but that can have a significant impact.

For example, the virtual disappearance of sunspots between 1645 and 1715 coincided with a period of intensely cold winters in Europe, part of the period dubbed the Little Ice Age. The lack of sunspots may have reduced solar radiation by a small amount, perhaps a quarter of a percent—enough to contribute to famines in Europe and allow glaciers to expand.

Although sunspots send comparatively little solar radiation into space, they are surrounded by bright areas with a high energy output. As a result, periods of sunspot activity see more overall solar radiation reaching Earth. Satellite measurements have detected a 0.1 swing in the Sun's total output during the course of an 11-year sunspot cycle.

That change appears to be too small to significantly affect global average temperatures in the lower atmosphere. But the ebb and flow of solar radiation can heat and cool the stratosphere enough to change its circulation patterns, which may have significant impacts on regional climate. In the case of the Little Ice Age, for example, Europe and North America felt the temperature drop most strongly.

The Sun may have other, more subtle climate impacts. Some researchers speculate that energy from the Sun may influence global temperatures indirectly by affecting the formation of clouds. Others speculate that plant growth, which appears to vary during solar cycles, may respond to variations in solar energy.

NCAR researchers develop powerful computer models to simulate the impact of the Sun on our climate. One such effort, the Whole Atmosphere Community Climate Model (WACCM), helps researchers home in on interactions among different levels of the atmosphere, ranging from the surface of Earth to the upper atmosphere and the edge of space. The modeling work is combined with analyses of data from observing instruments aboard satellites to track the impacts of solar energy throughout the atmosphere.

< previous | index

Home | Organization | Research | News | Education | Tools | Libraries | Search | News Feeds–RSS | Top

UCAR | NCAR | UCP | ©2009, UCAR | Privacy Policy | Terms of Use | Contact Us | Visit Us | Sponsored by

This document can be found at
Subscribe to our News Feeds at www.ucar.edu/news/rss