The exact causes of climate change remain a mystery to science. Many researchers link recent global warming to changes in the sun. Others remain skeptical, claiming that the sun varies only very slowly, over periods of millions of years. They say that no hard evidence exists for a solar effect on recent climate changes.
Now, new research may have provided just that evidence, with data demonstrating that solar variations have had major effects on the earth's climate as recent as 2,000 years ago. The research, conducted by a team of scientists from the Universities of Ohio, Minnesota, and Texas at Arlington, confirms that, during periods when the earth received less solar radiation, the Atlantic Ocean cooled, rainfall levels dropped, and North America experienced periods of intense drought. Some droughts lasted as long as a century.
Seven such events were detected, occurring once every 1,500 years, a period that matches the so-called "Bond Events" cycle of solar variation.
According to the study's lead author, Greg Springer, the correspondence provides "convincing evidence" of a solar effect on North American climate. "This really nails down the idea of solar influence on continental drought," said Springer.
The critical data was obtained from an 8-inch long stalagmite from a cave in West Virginia. As the stalagmite grew over a period of several thousand years, its composition precisely recorded fluctuations in the Earth's climate.