Two new studies (German and British) found a limit to how much manmade carbon dioxide can be added to the atmosphere before warming exceeds a 2 degrees Celsius or 3.6 degrees Fahrenheit increase. The world must put less than one trillion metric tons of carbon in the air during the first half of the 21st century to avoid the proverbial point of no return.
During the first nine years of this century the world emitted one-third of that amount, and if current rates continue, the world will emit one trillion metric tons in 20 years, said Malte Meinshausen, lead author of the German study.
About 234 billion metric tons of carbon were emitted through 2006, which means only 760 billion tons are left to emit, if the study’s levels are correct.
President Obama wants to cut U.S. carbon emissions by 80 percent. Bill Hare, co-author of German study, said that is a “good start but it’s not enough to limit warming.”
If other countries cut their per-person emission levels to match U.S. cuts, the U.S. would have to cut 90-95 percent to keep the world from exceeding one trillion ton level, Hare said.
Fewer amounts of fossil fuels must be burned to cut emissions. Three quarters of known reserves must be untouched the authors of the German study said. “Only a fast switch away from fossil fuels will give us a reasonable chance to avoid considerable warming,” said Mainshausen.
World carbon emissions have to start dropping by 2015 or cuts will be too “draconian,” according to Meinhausen.
Since the industrial revolution started, about 500 billion tons of carbon have been emitted, according to a University of Oxford study. The study says that one trillion metric tons of carbon will be a tipping point for climate change.
“Emitting carbon dioxide slower will not prevent dangerous climate change unless it involves phasing out carbon dioxide emissions altogether,” the study said.