Dbq Global Warming

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
Meltwater on the permafrost surface often forms shallow lakes. Katey Walter Anthony of the University of Alaska Fairbanks has found methane bubbling up from the lake bottoms. Many researchers have also found that permafrost can crack open into mini canyons called thermokarsts, which expose much greater surface area to the air, speeding melting and the release of greenhouse gases. And recent expeditions off Spitsbergen, Norway, and Siberia have detected plumes of methane rising from the ocean floor in shallow waters.
If you extrapolate from these burps of gas to wider regions, the numbers can get big enough to jolt the climate. Yet global measurements of methane do not necessarily show a recent increase. One reason is that hotspots "are still pretty local," says the University of Alaska Fairbanks's Vladimir E. Romanovsky, who charts permafrost temperatures. Another may be that scientists have just gotten better at finding hotspots that have always existed. That is why Dlugokencky says, "I am not concerned about a rapid climate change brought about by a change in
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