We have about a 50 percent chance of keeping global temperatures from rising dangerously higher than those of preindustrial times—if we leave most of the world’s remaining supply of oil, gas, and coal unearthed and unburned between now and 2050, according to a study published this week in the journal Nature.

Globally, about one-third of oil deposits must enter the no-burning zone, along with 88 percent of known and mineable coal supplies and about half the world’s unused natural gas. 

It adds up to about $6 trillion worth of fossil fuels, suggesting a revolutionary shake-up of the global financial and energy economies. Among them, about $3 trillion in global investments—including enormous funds like the California state pension fund—could find themselves busted by “stranded assets,” as the fuel reserves that energy companies calculate into their net worth would need to stay unused to avert the worst of climate change.

But which and how much of the world’s fossil energy deposits should remain buried? How about all the untapped fossil fuel deposits above the Arctic Circle, 75 percent of Canada’s tar sands, and more than 90 percent of Australian and U.S. coal.

The paper is a signal to countries with massive energy reserves that they must reconsider plans to extract those reserves if they want to fight climate change, said Mia Bennett, a Ph.D. student in geography at the University of California, Los Angeles, who manages the Cryopolitics blog.

“They think it represents a huge sum of money in the ground that they can drill up at will, but these reserves really represent a kind of carbon bubble,” Bennett said. “The assets could be rendered more or less worthless, given future developments on the energy market,” as well as in climate change policies and laws.

If reliable methods of capturing carbon emissions and keeping them out of the atmosphere come on line by 2025, we could help ourselves to a few more percentage points of coal, gas, and oil, the researchers determined. But there’s still a need to slash worldwide demand for fossil energy.

“Our results show that policy makers’ instincts to exploit rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to limiting global warming to no more than 2 degrees Celsius,” the study’s authors state. Slowing down fossil fuel development also renders moot projects that would spend big dollars on fossil fuel exploration and extraction, such as the Keystone pipeline.

The study took estimates for how much and what kinds of oil, gas, and coal supplies are left among the different fossil-fuel producing nations and geographic regions. If we keep burning fossil fuels over the next 40 years, previous studies have shown that we would pump about three times more heat-trapping greenhouse gas into the atmosphere than the world can withstand—if we hope to avoid dangerous temperature increases.

Among the measures to keep catastrophic warming at bay, researchers came up with the following solutions:

• Middle Eastern nations need to keep almost 40 percent of their oil resources unburned; the U.S. must leave 9 percent of its oil unburned; and Russia, 19 percent.

• But when it comes to coal, the U.S. and Australia need to leave 95 percent of remaining reserves in the ground; Africa, 90 percent; and Russia, 97 percent.

• Canada needs to wind down its tar sands industry almost immediately, leaving 75 percent of its oil supply in peace.

“This paper is looking ahead 30 years. No one’s going to read it and say, ‘We have to lock up the drills tomorrow,’ ” Bennett said. “But the main takeaway is that we have to start reinvesting and reprioritizing away from fossil fuels, possibly a lot faster than some people would like.”

Jan 8, 2015