http://www.scientificamerican.com/?WT.mc_id=SA_syn_accuweather

How Much Will Tar Sands Oil Add to Global Warming?

By David Biello
1/24/2013 11:38:10 AM

James Hansen has been publicly speaking about climate change since 1988. The NASA climatologist testified to Congress that year and he's been testifying ever since to crowds large and small, most recently to a small gathering of religious leaders outside the White House last week. The grandfatherly scientist has the long face of a man used to seeing bad news in the numbers and speaks with the thick, even cadence of the northern Midwest, where he grew up, a trait that also helps ensure that his sometimes convoluted science gets across.

TAR SANDS: At least 170 billion barrels of oil could be extracted from Alberta's oil sands deposits with today's technology. Image: © David Biello

This cautious man has also been arrested multiple times.

His acts of civil disobedience started in 2009, and he was first arrested in 2011 for protesting the development of Canada's tar sands and, especially, the Keystone XL pipeline proposal that would serve to open the spigot for such oil even wider. "To avoid passing tipping points, such as initiation of the collapse of the West Antarctic Ice Sheet, we need to limit the climate forcing severely. It's still possible to do that, if we phase down carbon emissions rapidly, but that means moving expeditiously to clean energies of the future," he explains. "Moving to tar sands, one of the dirtiest, most carbon-intensive fuels on the planet, is a step in exactly the opposite direction, indicating either that governments don't understand the situation or that they just don't give a damn."

He adds: "People who care should draw the line."

Hansen is not alone in caring. In addition to a groundswell of opposition to the 2,700-kilometer-long Keystone pipeline, 17 of his fellow climate scientists joined him in signing a letter urging Pres. Barack Obama to reject the project last week. Simply put, building the pipeline-and enabling more tar sands production-runs "counter to both national and planetary interests," the researchers wrote. "The year of review that you asked for on the project made it clear exactly how pressing the climate issue really is." Obama seemed to agree in his second inaugural address this week, noting "we will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations."

At the same time, the U.S. imports nearly nine million barrels of oil per day and burns nearly a billion metric tons of coal annually. China's coal burning is even larger and continues to grow by leaps and bounds. Partially as a result, global emissions of greenhouse gases continue to grow by leaps and bounds too-and China is one alternative customer eager for the oil from Canada's tar sands. Neither developed nor developing nations will break the fossil-fuel addiction overnight, and there are still more than a billion people who would benefit from more fossil-fuel burning to help lift them out of energy poverty. The question lurking behind the fight in North America over Keystone, the tar sands and climate change generally is: How much of the planet's remaining fossil fuels can we burn?

The trillion-tonne question

To begin to estimate how much fossil fuels can be burned, one has to begin with a guess about how sensitive the global climate really is to additional carbon dioxide. If you think the climate is vulnerable to even small changes in concentrations of greenhouse gases-as Hansen and others do-then we have already gone too far. Global concentrations of greenhouse gases in the atmosphere have reached 394 parts per million, up from 280 ppm before the Industrial Revolution and the highest levels seen in at least 800,000 years. Hansen's math suggests 350 ppm would be a safer level, given that with less than a degree Celsius of warming from present greenhouse gas concentrations, the world is already losing ice at an alarming rate, among other faster-than-expected climate changes.

International governments have determined that 450 ppm is a number more to their liking, which, it is argued, will keep the globe's average temperatures from warming more than 2 degrees C. Regardless, the world is presently on track to achieve concentrations well above that number. Scientists since chemist Svante Arrhenius of Sweden in 1896 have noted that reaching concentrations of roughly 560 ppm would likely result in a world with average temperatures roughly 3 degrees C warmer-and subsequent estimates continue to bear his laborious, hand-written calculations out. Of course, rolling back greenhouse gas concentrations to Hansen's preferred 350 ppm-or any other number for that matter-is a profoundly unnatural idea. Stasis is not often found in the natural world.

Concentrations of greenhouse gases in the atmosphere may not be the best metric for combating climate change anyway. "What matters is our total emission rate," notes climate modeler Ken Caldeira of the Carnegie Institution for Science Department of Global Ecology at Stanford University, another signee of the anti-Keystone letter. "From the perspective of the climate system, a CO2 molecule is a CO2 molecule and it doesn't matter if it came from coal versus natural gas."

...Continue the article

Continue Reading on ScientificAmerican.com >