The world must burn less than one-quarter of its remaining fossil fuel reserves if it is to avoid dangerous climate change, according to new research.
Two studies published today in the journal Nature warn that the world must limit its total carbon dioxide emissions to about 1 trillion tons by 2050 to have the best chance at holding temperature rise below 2 degrees Celsius.
That's the target identified by some scientists and many governments that believe warming beyond that point could greatly increase the chance of catastrophic -- and in some cases, irreversible -- changes in the world's climate.
The bottom line is simple, said Myles Allen of Oxford University, the lead author of one of the new studies. "Every ton [of carbon dioxide] you release now is a ton you won't be able to release in 50 years' time," he said. "The longer we postpone emissions reductions, the harder we make the task when the time comes around."
To stay under that 1 trillion ton limit, governments would have to sharply reduce their greenhouse gas emissions from current levels. Malte Meinshausen, lead author of one study, said the world's total CO2 emissions could reach 1 trillion tons in just 20 years.
If no climate policies are implemented (red), global warming will cross 2 degrees Celsius by the middle of the century. Strong action to mitigate emissions (blue) would limit the risk of exceeding 2 degrees to 25 percent. Graph courtesy of M. Meinshausen.
"We've already emitted a third of that in the past nine years, from 2000 to 2009," explained Meinshausen, a professor at the Potsdam Institute for Climate Impact Research in Germany.
And Meinshausen's study suggests the true "carbon dioxide budget" could be even lower if the warming effects of other greenhouse gases, such as methane, are taken into account.
But even achieving the limit recommended by the new studies isn't a guarantee that the world will avoid serious climate change, experts said.
More at:
http://www.nature.com/nature/journal/v458/n7242/full/4581077a.html
