Sun Spot-Climate Link
Small changes in the energy output of the sun can have a major impact on global weather patterns, such as the intensity of the Indian monsoon, that could be predicted years in advance, a team of scientists said.
The sun swings through an 11-year cycle measured in the number of sun spots on the surface that emit bursts of energy.
The difference in energy is only about 0.1 percent between a solar maximum and minimum and determining just how that small variation affects the world's climate has been one of the great challenges facing meteorologists.
Using a century of weather observations and complex computer models, the international team of scientists led by the National Center for Atmospheric Research (NCAR) in the United States showed that even a small increase in the sun's energy can intensify wind and rainfall patterns.
"Small changes in the sun's output over the 11-year solar cycle have long been known to have impacts on the global climate system," said Julie Arblaster, from the Center for Australian Weather and Climate Research, a co-author of the study published in the latest issue of the journal Science.
"Here we reconcile for the first time the mechanisms by which these small variations get amplified, resulting in cooler sea surface temperatures in the tropical Pacific and enhancing off-equatorial rainfall."
The researchers found that during periods of strong solar activity the air in the upper atmosphere, in a layer called the stratosphere, heats up. This occurs over the tropics, where sunlight is typically most intense.
The extra warming alters wind patterns in the upper atmosphere, which in turn increases tropical rainfall.