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GLOBAL WARMING: Faster Than Expected?
Authors:
Carey, John
Source:
Scientific American; Nov2012, Vol. 307 Issue 5, p50-55, 6p Document Type:
Article
Subject Terms:
*GLOBAL warming -- Mathematical models
*CLIMATIC changes
*HISTORY
*MELTWATER
*ENVIRONMENTAL aspects
*PERMAFROST
*SEA ice -- Thawing
*METHANE -- Environmental aspects
*CARBON dioxide -- Environmental aspects
*SEA level
TROPICS -- Climate
Geographic Terms:
TROPICS
Abstract:
The article discusses the predicted rate of global warming, which could be affected by global feedback mechanisms such as the alteration of ocean currents due to meltwater, the release of carbon dioxide and methane from permafrost in Alaska and Siberia, and the global loss of ice. The melting of sea ice and the rise of sea levels are discussed, and side effects of global warming such as drought, coastal floods, and wildfires. The history of global climate change, the effects of organic carbon, and the release of methane from anaerobic decomposition in tropical wetlands are discussed. INSET: IN BRIEF. Full Text Word Count:

3481
ISSN:
00368733
Accession Number:
82946695
Database:
Academic Search Complete

Section:
ENVIRONMENT
Loss of ice, melting of permafrost and other climate effects are occurring at an alarming pace IN BRIEF
Scientists thought that if planetary warming could be kept below two degrees Celsius, perils such as catastrophic sea-level rise could be avoided. Ongoing data, however, indicate that three global feedback mechanisms may be pushing the earth into a period of rapid climate change even before the two degree C "limit" is reached: meltwater altering ocean circulation; melting permafrost releasing carbon dioxide and methane; and ice disappearing worldwide. The feedbacks could accelerate warming, alter weather by changing the jet stream, magnify insect infestations and spawn more and larger wildfires. OVER THE PAST DECADE SCIENTISTS THOUGHT THEY HAD FIGURED OUT HOW TO PROTECT humanity from the worst dangers of climate change. Keeping planetary warming below two degrees Celsius (3.6 degrees Fahrenheit) would, it was thought, avoid such perils as catastrophic sea-level rise and searing droughts. Staying below two degrees C would require limiting the level of heat-trap-ping carbon dioxide in the atmosphere to 450 parts per million (ppm), up from today's 395 ppm and the preindustrial era's 280 ppm. Now it appears that the assessment was too optimistic. The latest data from across the globe show that the planet is changing faster than expected. More sea ice around the Arctic Ocean is disappearing than had been forecast. Regions of permafrost across Alaska and Siberia are spewing out more methane, the potent greenhouse gas, than models had predicted. Ice shelves in West Antarctica are breaking up more quickly than once thought possible, and the glaciers they held back on adjacent land are sliding faster into the sea. Extreme weather events, such as floods and the heat wave that gripped much of the U.S. in the summer of 2012 are on the rise, too. The conclusion? "As scientists, we cannot say that if we stay below two degrees of warming everything will be fine," says Stefan Rahmstorf, a professor of physics of the oceans at the University of Potsdam in Germany. The X factors that may be pushing the earth into an era of rapid climate change are long-hypothesized feedback loops that may be starting to kick in. Less sea ice, for example, allows the sun to warm the ocean water more, which melts even more sea ice. Greater permafrost melting puts more CO2 and methane into the atmosphere, which in turn causes further permafrost melting, and so on. The potential for faster feedbacks has turned some scientists into vocal Cassandras. Those experts are saying that even if nations do suddenly get serious about reducing greenhouse gas emissions enough to stay under the 450-ppm limit, which seems...
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