Global warming - including periods of intense warming lasting tens of thousands of years - occurred more frequently in the past than previously believed, U.S. researchers say.
Releases of carbon dioxide sequestered in the deep oceans were the most likely trigger of these ancient "hyperthermal" events, a team led by the Scripps Institution of Oceanography at the University of California, San Diego said.
Most of the events raised average global temperatures between 3.6 and 5.4 degrees Fahrenheit, an amount comparable to current estimates of how much temperatures are expected to rise in coming decades as a consequence of human-caused global warming, a UCSD release reported Wednesday.
Hyperthermals provide historical perspective on what Earth will experience as it continues to warm from widespread use of fossil fuels, Scripps geology Professor Richard Norris said.
"There are lots of ancient examples of global warming on a scale broadly like the expected future warming.
"These hyperthermals seem not to have been rare events," he said. "We can use these events to examine the impact of global change on marine ecosystems, climate and ocean circulation."
The hyperthermals took place roughly every 400,000 years during a warm period of Earth's history that prevailed some 50 million years ago and lasted about 40,000 years before temperatures returned to normal, he said.
Source: UPI
Global Warming Occurred Tens of Thousands of Years Ago
Mar 17, 2011, 11:12