Changes In Solar Activity Have Little Effect On Climate
Brett Smith for redOrbit.com – Your Universe Online
From the Medieval Climate Anomaly to the Little Ice Age, average temperatures on Earth have varied significantly over the past thousand years. And according to a new study in Nature Geoscience that variation has little to do the amount of activity from the Sun.
The Medieval Climate Anomaly, which lasted from approximately 950 to 1250, was a warming period in certain regions. The Little Ice Age, which lasted from about 1450 to 1850, is the term used to describe a period of widespread regional cooling. Previous research has linked periods of high and low solar activity, respectively, to these separate climate phenomena.
In the study, the scientists from the University of Edinburgh tried to determine causes of climate change in the Northern Hemisphere over the past 1,000 years. The Scottish team used data culled from tree rings and other historical sources that was compared to computer-based models of past climate and variations in solar activity.
The team found that until the year 1800, the main driver of episodic changes in climate was volcanic activity. The scientists noted that debris and particles from volcanic eruptions can prevent sunlight from reaching the Earth, resulting in a cooler and drier climate. Since 1900, greenhouse gas emissions have driven changes in average global temperatures, the scientists said.
“Until now, the influence of the sun on past climate has been poorly understood,” said Andrew Schurer, a geoscientist at the University of Edinburgh. “We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future.”
“We find that neither a high magnitude of solar forcing nor a strong climate effect of that forcing agree with the temperature reconstructions,” the researchers wrote in the study. “We instead conclude that solar forcing probably had a minor effect on Northern Hemisphere climate over the past 1,000 years, while, volcanic eruptions and changes in greenhouse gas concentrations seem to be the most important influence over this period.”
Earlier this month, the National Research Council called for a climate change early-warning system that could anticipate sudden changes and impacts in a report published by The National Academic Press.
“Research has helped us begin to distinguish more imminent threats from those that are less likely to happen this century,” said report author James W.C. White, professor of geological sciences at the University of Colorado, Boulder. “Evaluating climate changes and impacts in terms of their potential magnitude and the likelihood they will occur will help policymakers and communities make informed decisions about how to prepare for or adapt to them.”
According to the report, abrupt climate changes and impacts already under way are of immediate concern, including the loss of late-summer Arctic sea ice and the rise in extinction rates of marine and terrestrial species.