The long-term effects of global warming may be felt for another 10,000 years, if past warming events are any prediction.
"In 100 to 300 years, we could produce a signal on Earth that takes tens of thousands of years to equilibrate, judging from the geologic record," said paleoceanographer Richard Norris of the Scripps Institution of Oceanography at the University of California in San Diego in a press release.
Norris bases his direful prediction on a recent study he co-authored in the journal Nature along with Phil Sexton of the Open University in the United Kingdom, and other paleoclimatologists.
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Bursts of intense global warming that lasted tens of thousands of years occurred about every 400,000 years, roughly 40 million years ago. The most famous of these warming events, known as the Paleocene-Eocene Thermal Maximum, increased temperatures by 4 and 7 degrees Celsius (7.2 and 12.6 degrees Fahrenheit) and lasted about 170,000 years. But the team found that more moderate versions of these type of warming events called “hyperthermals,” were 3 times more frequent than previously suspected and once initiated it took around 40,000 years for Earth's temperatures to return to normal.
These more modest warming events were between 2 and 3 degrees Celsius (3.6 and 5.4 degrees Fahrenheit), similar to those expected to occur as a result of modern human-induced carbon emissions.
"These hyperthermals seem not to have been rare events," Norris said, "hence there are lots of ancient examples of global warming on a scale broadly like the expected future warming. We can use these events to examine the impact of global change on marine ecosystems, climate, and ocean circulation," said Norris.
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The evidence for the ancient climate change comes from sediment records taken from off the coast of South America. Warm periods were marked by gray layers in the ocean sediments caused by the calcium-containing microorganisms dissolving into acidic oceans. Layers from normal years are greenish.
The same ocean acidification problem is happening right now, causing serious damage to coral reefs and messing with the breeding cycles of sea creatures.
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Further study of other sediment samples from the North Sea will enable Norris and his colleagues to more finely tune the frequency of the hyperthermals. Sediments there are finely layered enough for scientists to distinguish changes from year to year. The team is also interested to investigate whether carbon dioxide from deep in the ocean may have caused these ancient intensified greenhouse periods in Earth's history and the role the Earth's carbon reservoirs played in the planet's recovery from the temperature and carbon spikes.
Tags: Carbon Emissions, Chemistry, Climate Change, Corals, Geology
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