Sea surface temperatures. (Credit: Plumbago/CC BY-SA 3.0)
According to a University of Maryland press release, an examination of multiple studies covering the globe showed scientists that the reversal of a 1,800-year global cooling trend was caused by human activity that resulted in global warming.
Researchers examined 57 studies of ocean surface temperature data covering a 200-year span over the entire globe. The cooling trend was believed to be largely the result of frequent volcanic activity which spurred a significant cooling trend. The trend also was due to the tendency of oceans to change temperature slowly, as opposed to land masses, which change temperature more quickly.
Due to human influence, however, the globe is warming 20 times faster than it cooled for the 1,800 years previously, researchers discovered. To determine the cause of the cooling trend, the scientists turned to climate models and looked at the influence of different “forcing factors” on the results. These factors included volcanic activity, land use and Earth’s orbit, among others.