updated 12/10/2008 4:52:34 PM ET 2008-12-10T21:52:34

As humanity wrings ever more fossil fuels from our planet, the question of when the taps will start to run dry — when "peak oil" will occur — looms ever closer on the horizon. Some say a decade, maybe two. Some say it's already passed. No one is sure.

Whatever the answer, new research has come to the ominous conclusion that slackening oil and gas supplies could actually accelerate the pace of global warming.

If it seems counter-intuitive, consider that generating a kilowatt hour of energy by burning oil pumps 274 grams of the greenhouse gas carbon dioxide into the atmosphere. Natural gas is cleaner, accounting for 202 grams. But coal is by far the worst polluter, clocking in at 331 grams of CO2 per kilowatt hour (a kilowatt hour is when 1000 watts of energy is used for one hour).

As the oil and gas begin to dry up, coal could move in to fill the demand for energy, Pushker Kharecha of the Goddard Institute for Space Studies at Columbia University explained. And unless the carbon it emits is captured and sequestered underground, it will saturate the atmosphere, pushing temperatures ever higher and worsening a host of global environmental problems.

In a series of calculations, Kharecha and co-author James Hansen, also of Goddard, suggest that major climate damage could be avoided even if oil and gas production continue unabated, and are allowed to peter out as reserves dwindle.

"Those two fossil fuels couldn't keep us in the danger zone for very long," Kharecha said, referring to a CO2 concentration of 350 parts per million in the atmosphere or higher.

Right now, the concentration is about 385 part per million, which Kharecha said is already "undesirably high," adding, "but we must reduce coal emissions. Coal has the potential to keep us in the danger zone for a very long time, well past the year 2150."

Kharecha and Hansen will present their work in San Francisco next week at the Fall meeting of the American Geophysical Union.

Kevin Gurney of Purdue University said the world is even more addicted to coal than it is to oil because it is cheap and abundant. And that's not likely to change in the near future.

As peak oil begins to dictate the need for new sources of energy around the world, he said "I unfortunately think that without serious leadership intervention, we are going to trundle along and start using coal."

"Of course there could be some kind of fuel crisis, or the president could put his career on the line and embrace a green economy, or there could be a profound technological breakthrough," he said. "But failing something like that, I just don't see how we're going to make a dent in the energy generation mix."

Kharecha, however, remains optimistic that the story of humans' influence on climate can still have a happy ending.

"Peak oil and gas can really go both ways," Kharecha said. "If people choose to use coal, oil sands, methane, or other fossil fuels as a substitute, that's going to be a major problem. But if it spurs society to realize we need to wean ourselves off fossils fuels, it could be a huge boon for climate."

© 2012 Discovery Channel

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