What if US quits climate deal? Doesn't look good for Earth

http://www.bostonherald.com/business/business_markets/2017/05/what_if_us_quits_climate_deal_doesnt_look_good_for_earth

Associated Press Sunday, May 28, 2017

Earth is likely to reach more dangerous levels of warming even sooner if the U.S. retreats from its pledge to cut carbon dioxide pollution, scientists said. That's because America contributes so much to rising temperatures.

President Donald Trump, who once proclaimed global warming a Chinese hoax, said in a tweet Saturday that he would make his "final decision" this coming week on whether the United States stays in or leaves the 2015 Paris climate change accord in which nearly every nation agreed to curb its greenhouse gas emissions.

Leaders of seven wealthy democracies, at a summit in Sicily, urged Trump to commit his administration to the agreement, but said in their closing statement that the U.S., for now, "is not in a position to join the consensus."

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In an attempt to understand what could happen to the planet if the U.S. pulls out of Paris, The Associated Press consulted with more than two dozen climate scientists and analyzed a special computer model scenario designed to calculate potential effects.

Scientists said it would worsen an already bad problem and make it far more difficult to prevent crossing a dangerous global temperature threshold.

Calculations suggest it could result in emissions of up to 3 billion tons of additional carbon dioxide in the air a year. When it adds up year after year, scientists said that is enough to melt ice sheets faster, raise seas higher and trigger more extreme weather.

"If we lag, the noose tightens," said Princeton University climate scientist Michael Oppenheimer, co-editor of the peer-reviewed journal Climatic Change.

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Even with the U.S. doing what it promised under the Paris agreement, the world is likely to pass that 2 degree mark, many scientists said.

But the fractions of additional degrees that the U.S. would contribute could mean passing the threshold faster, which could in turn mean "ecosystems being out of whack with the climate, trouble farming current crops and increasing shortages of food and water," said the National Center for Atmospheric Research's Kevin Trenberth.

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