A study that links the sun's brightness to rainfall in the Western United States suggests the region's long drought may end soon.
"This is the year the desert Southwest should pick up the rain. If it doesn't rain this year, we may have to wait another two years," said Charles A. Perry, a hydrologist with the U.S. Geological Survey's Water Resources Division in Lawrence, Kansas.Parts of the Pacific Northwest where rainfall has been below normal should be wetter than normal, Perry said Monday during the American Geophysical Union's fall meeting.
Perry's forecast is controversial because it is based on a theoretical link between solar brightness and weather on Earth. Other purported connections, such as between sunspots and rainfall, often have proven wrong after more detailed study, he acknowledged.
In his study, Perry said he found a statistically significant correlation between the sun's brightness on a monthly basis and the amount of precipitation four years later in the Pacific Northwest and three to five years later in the Southwest.
The sun's brightness sharply increased during 1987-88, so above-normal rain is likely in the Northwest next year and in the Southwest either soon or two years from now, Perry said.
"The persistent drought in the Western states from 1985-90 coincides with a period of decreasing solar irradiance that occurred between 1981-86," Perry's study said.
His theory is that when the sun is brighter, more solar energy is absorbed by tropical oceans. Major ocean currents take three to five years to carry the warmer water to the West Coast, where it results in increased evaporation of seawater and more rainfall, Perry believes.
Perry's theory also suggests the increased solar brightness during 1987-88 may strengthen the El Nino - a potentially damaging weather pattern - that started this year.
An El Nino in 1982-83 was the strongest in a century, and was blamed for aggravating African and Australian droughts, blasting California with a series of wet winter storms and drenching Peru and Ecuador. It killed 1,500 people and caused $2 billion to $8 billion in damage, according to the United Nations.
Perry said the 1982-83 El Nino came three years after the largest increase in solar brightness since 1950.