Sunny vindication?

Abstract

Scientists have generally agreed that Earth's temperature has risen slightly during the past 100 years, by about 0.6°, in fact. But they have not been able to agree why. For one thing, the Sun has been a spoiler in the debate. While many scientists believe that greenhouse gases or even purely natural climate variations are to blame, others have insisted that the Sun may be a player in climate changes on Earth. The Sun maybe getting brighter or variations in the solar cycle may be driving temperature changes, they suggest. Because the Sun is difficult to remove from the equation, the issue has remained unsettled. Now in the April 7 issue of Science, David Thomson of AT&T Bell Laboratories in Murray Hill, N.J., may have brushed away some of the clouds. Using sophisticated techniques to study the statistical structure of time series, Thomson analyzed more than 300 years of temperature records. He found little evidence that the Sun is altering Earth's temperatures. In fact, he determined that the amplitude of the seasonal cycle is decreasing, which clashes with what would be expected if the Sun were getting brighter. He claims his finding “implies that solar variability cannot be the sole cause of the increasing temperature over the last century.” Though the Sun may play some role in climate change, Thomson writes in Science that the implications of his analysis are that “the effects of increasing greenhouse gases may be worse than previously thought.” Moreover, he writes, the finding calls for a reexamination of various climate parameters from orbital effects to seasonal temperature differences to annual temperature cycles.