quinta-feira, 7 de outubro de 2010

Study shines new light on Sun's role in Earth's climate


London, England (CNN) -- A new study has shed light on the sun's impact on the Earth's climate, confounding current thinking about solar cycles and how they influence temperatures on Earth.
Previously scientists had thought that radiation reaching the Earth rises and falls in line with the Sun's activity, which during the 11-year solar cycle goes though periods of low and high activity.
But research by Imperial College, London and the University of Colorado in the U.S. examining solar radiation levels from 2004 to 2007 -- a period of declining solar activity -- revealed that levels of visible radiation reaching the Earth actually increased during the period.
Using data collected by NASA's SORCE (SOlar Radiation and Climate Experiment) satellite, which launched in 2003, the scientists were able to scrutinize the full solar spectrum -- x-ray, ultraviolet (UV), visible (VR), near-infrared, and total solar radiation -- and compare it to earlier, less comprehensive data.
Joanna Haigh, leader author of the study published in the journal Nature told CNN: "What the data has shown, rather unexpectedly, is that the decline in ultra-violet radiation is much larger than anticipated. But more surprisingly the visible radiation actually increased as solar activity was declining".
CNN