Climate change may have reached the point of no return last month.
CO2 levels in the atmosphere topped 400 parts per million on May 19, for the first time since the Pleistocene era, over 2.5 million years ago. President Barack Obama’s historic speech on climate change today highlights his growing focus on this issue for his second term.
Climate scientists have long regarded that 400 number as the symbolic threshold. One step beyond, and it would be virtually impossible to put the brake on human-generated climate change. The bad news escalated last week when the International Energy Agency reported that global emissions of carbon dioxide rose 1.4 percent in 2012, the largest annual increase on record.
The good news, by contrast, is that while CO2 emissions rise elsewhere, in the United States at least they have been going down, and are now at their lowest level in more than two decades. “Over the last four years,” Obama boasted in his State of Union address, “our emissions of the dangerous carbon pollution that threatens our planet have actually fallen.”
True. The United States, however, has succeeded in lowering CO2 emissions because of the continuing natural gas boom from fracking. Lured by record low prices, about 150 U.S. coal-fired power plants have switched to natural gas in the last three years. Gas produces half the CO2 that coal does when burned, and almost none of the sooty particulates, which contribute to asthma and other respiratory illnesses.
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