Greenhouse-driven climate change is not only unavoidable now, it will happen faster than humans can adapt, scientists say. As CO2 levels rise, they rise faster -- by about 2 ppm per year -- 100 times faster than at the end of the Ice Age.
When first measured in 1958, CO2 levels were at 315 ppm. The dangerous momentum we're seeing now -- the number had risen to 390 ppm by 2011 -- could push greenhouse emissions to 450 PPM, warming the planet by another 2 degrees and bringing the return of a global climate that hasn't existed since the Pliestocene Era 2 million years ago, before humans evolved. Greenland was forested then, and sea levels as much as 66 feet higher.
It would take an estimated 1,000 years to reverse the conditions created by climate change, during which large swaths of the planet would be desertified due to permanent drought conditions and famine could affect as much as half of the world's human population.
Over the last 150 years -- mostly since the Second World War -- humans have been recklessly destroying the atmosphere -- Earth's protective sheath, which created the conditions under which human civilization has flourished. Every second, the world's smokestacks and cars pump 2.4 million pounds of heat-trapping CO2 into the air, where it will remain for hundreds to thousands of years.
Humans put 38.2 billion tons of CO2 into the air in 2011. China, world leader in greenhouse emissions, pumps out 10 billion tons of CO2 a year, its emissions rising about 10% annually. The U.S., the world's second biggest greenhouse polluter, has slowly lowered its emissions to 5.9 billion tons per year.