Friday, September 11, 2015

Climate scientists fear ‘Day After Tomorrow’ scenario

[MSNBC] In the 2004 disaster-flick “Day After Tomorrow,” abrupt man-made climate change knocks the planet into a state of utter chaos. At the time, the movie’s vision of the apocalypse wasn’t seen as realistic. But that’s begun to change.  
Two new studies deepen the fear that global warming could shut down the circulation of the oceans, much as the movie portrays, dropping vast stretches of Asia into drought and exposing the whole Northern Hemisphere to severe ice and snow.
Unlike gradual climate change, where the planet warms steadily, this change would be sudden and sharp enough to roil civilization—happening in as little as three years and resulting in as much as an 18-degree Fahrenheit drop in average temperatures.
Jud Partin is the lead author of the stronger of the two studies, supported by the National Science Foundation and published in the journal Nature Communication. He’s also a geophysicist at the University of Texas, and an unabashedly close viewer of a certain summer blockbuster starring Dennis Quaid as hero-scientist Jack Hall.
“In the movie they defy the laws of physics,” Partin told msnbc, referring to hurricanes that form over land and other impossible weather. “But they got the climate science more or less right.”
The climate science deals with the “Atlantic thermohaline circulation,” an oceanic conveyor belt that carries heat from the tropics to the north, where it warms Western Europe and Eastern North America. It’s a fragile pattern, dependent on precise levels of salinity; Partin and others believe it could stop as Greenland’s ice sheets melt, flooding the ocean with fresh water.
To glimpse our possible future, Partin and his colleagues gathered new geological data and re-examined the deep past. They looked at an earlier, all-natural melt-off that happened about 12,000 years. Known as the “Younger Dryas,” the period was defined by a deep chill across the northern latitudes.
Ice core studies cited by Partin show an 18-degree Fahrenheit drop in average temperatures across Greenland. New York and London would be slightly warmer, he believes, but still frigid with average temperature drops of at least a dozen degrees. That might seem small, but even minute changes in the average are a signal of extreme swings in actual conditions.
And the effects of this temperature change would be felt in a matter of years or decades, rather than a century or longer. That’s because this part of the climate system seems to work more like a switch than a dial. Once a certain threshold is reached, there’s a big, fast swing in the conditions over large parts of the planet.  
“It would definitely change everyday life in Europe and North America,” Partin told MSNBC. “Daily life would be drastically affected in these areas, in ways I can’t imagine or begin to address.” Read More