Curbing coal emissions alone might avert climate danger, say researchers
September 12, 2008
Satellite imagery shows where carbon dioxide is being emitted or absorbed, measured here in 2003. Reds show sources; blues, absorption. Image: NASA
An ongoing rise in atmospheric carbon dioxide from burning of fossil fuels might be kept below harmful levels if emissions from coal are phased out within the next few decades, say researchers. They say that less plentiful oil and gas should be used sparingly as well, but that far greater supplies of coal mean that it must be the main target of reductions. Their study appears in the journal Global Biogeochemical Cycles.
The burning of fossil fuels accounts for about 80 percent of the rise of atmospheric CO2 since the pre-industrial era, to its current level of 385 parts per million. However, while there are huge amounts of coal left, predictions about when and how oil and gas production might start running out have proved controversial, and this has made it difficult to anticipate future emissions. To better understand how the emissions might change in the future, climatologist Pushker Kharecha and director James Hansen of NASA Goddard Institute for Space Studies—a member of Columbia University's Earth Institute--considered a wide range of scenarios.
"This is the first paper that explicitly melds the two vital issues of global peak oil production and human-induced climate change," Kharecha said. "We found that because coal is much more plentiful than oil or gas, reducing coal emissions is absolutely essential to avoid dangerous climate change." Kharecha is also author of a related article, "How Will the End of Cheap Oil Affect Future Global Climate?"
CO2, which accounts for about half of the human-caused greenhouse gases in the atmosphere, concerns scientists because it can remain for centuries. Hansen's previous research suggests that a dangerous level of global warming may occur if CO2 exceeds a concentration of about 450 parts per million. That is a 61 percent increase from the pre-industrial level of 280 parts per million, but only 17 percent more than the current level. Hansen says the danger level would bring a rise of about 1.8°F above the 2000 global temperature. At or beyond this point, disintegration of the West Antarctic ice sheet and Arctic sea ice could reach tipping points, and set in motion feedback mechanisms that would lead to further, accelerated melting.
To better understand the possible trajectory of future CO2, Kharecha and Hansen devised five emissions scenarios spanning the years 1850 to 2100. Each reflects a different estimate for the global production peak of fossil fuels, the timing of which depends on reserve size, recoverability and available technology. "Even if we assume high-end estimates and unconstrained emissions from conventional oil and gas, we find that these fuels alone are not abundant enough to take carbon dioxide above 450 parts per million," Kharecha said.
The first scenario estimates CO2 levels if emissions from fossil fuels follow "business as usual," growing 2 percent annually until half of each reservoir has been recovered. After this, emissions begin to decline by 2 percent annually. In the second scenario, emissions from coal are reduced, first by developed countries starting in 2013, and then by developing countries a decade later, leading to a global phaseout of emissions by 2050. The phaseout could come either from reducing coal consumption or by capturing and trapping CO2 from coal burning before it reaches the air.
The remaining three scenarios include the phaseout of coal, but consider different scenarios for oil use and supply. One case considers a delay in the oil peak by about 21 years to 2037. Another considers fewer-than-expected additions to currently proven reserves, or taxes on emissions that makes fuels too expensive to extract. The final scenario looks at emissions from oil fields that peak at different times, extending the peak into a plateau that lasts from 2020-2040.
The team used a mathematical model to convert CO2 emissions from each scenario into estimates of future concentrations in the atmosphere. The "business as usual" scenario resulted in CO2 that would exceed 450 parts per million from by 2035, and climb to more than double the pre-industrial level. Even when low-end estimates of reserves were assumed, the threshold was exceeded from about 2050 onwards. However, the other four scenarios resulted in CO2 levels that peaked in various years, but all fell below the prescribed cap of 450 parts per million by about 2080 at the latest. Levels in two of the scenarios always stayed below the threshold.
The researchers say that the results clearly imply that emissions from coal should be reduced. This would apply also, they say, to "unconventional" fuels not yet in mainstream use, such as methane hydrates and tar sands. These also contain far more fossil carbon than conventional oil and gas, and thus could potentially be major contributors to emissions.
"We're illustrating the types of action needed to get to target carbon dioxide levels," Kharecha said. "The most important mitigation strategy we recommend—a phase-out of carbon dioxide emissions from coal within the next few decades—is feasible using current or near-term technologies."
The article "How will the end of cheap oil affect future global climate?" is at: http://www.giss.nasa.gov/research/briefs/kharecha_01/
Source: The Earth Institute at Columbia University
Nov 24, 2009 |
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I was under the belief that coal was one of the cleanest of the fossil fuels. Shouldn't they be looking to shut down oil plants seeing as it's a limited resource and very dirty?
You are wrong tough about coal being clean, actually it has the highest carbon content of all fossile fuels.
But you know some call it pollution some call it life... Being cynical here.
Repeal the Price-Anderson Act to return liability to the nuke industry, from the taxpayers, and the nuclear industry will do a rapid disappearing act; not to be missed.
As for the fear of nuclear front, I'd rather have a nuke plant in my town than any fossil fuel plant. The problems with nuke reactiors were the technology behind them was in an almost infant stage. We've done a lot to make the process, as well as the fuel disposal safer and cheaper. What bothers me are the regulations preventing us from replacing the aging and dirtier plants with new nuclear plants.
Only in anti-nuke fantasy land.
Back in the real world uranium is one of the minerals with the highest ratio of reserves to consumption and is relatively unexplored. The cost of uranium is a miniscule part of the amortized cost of nuclear power and far lower ore grades can be mined with small impact on the economics of nuclear power; unlocking potentially hundreds of times more uranium than we've yet mined using volcanic deposits, phopshate rock and possibly sea water(with ion exchangers) if that can be scaled up.
Modern reactors like pebble beds(South Africas PBMR or China's HTR-PM) and molten salt reactors(like the Fuji MSR developed by a consortium with members from countries such as Japan, US and Russia) are currently under development and can achieve far higher burn-up.
The average piece of the Earth's crust has about 3 grams of uranium and 9 grams of thorium. Properly utilized(e.g. in an MSR) that has the same heating value as more than 100 barrels of oil.
Fuel consumption is unlikely to ever be a serious constraint for anything but light water reactors. We may phase out fission because we find something cheaper or better, but it's not going to be because of fuel.
It is by a wide margin the dirtiest fossil fuel whether or not you're concerned about global warming; particulates, NOx, SOx, mercury, arsenic, cadmium and other heavy metals. The cleanest fossil fuel is natural gas.
Those pollutants have a half-life of forever; by the standards applied to nuclear power you must immobilize them and burry them in a geologically stable repository until the Earth is gobbled up by the sun.
You're also going to be required to sequester or neutralize that CO2.
If you crunch the numbers a disaster of a sufficient scale is so ridiculously unlikely that it has essentially no impact on the economics of insurance for nuclear power.
And just why is it that dams that have the potential to kill tens of thousands and destroy millions of homes(see the banqiao dam failure) with a far greater probabillity do not require such insurance in the first place?
Just sticking that CO2 down an old gas well isn't going to work; what if by a one in a million chance a few cubic miles of CO2 are released and suffocate a few hundred thousand people in a nearby town? Looks like you'll be a needing a price Anderson-Act for coal if you apply the same standards as is done to nuclear energy.
Surely, if this does happen, Al Gore will say this is proof of global warming.
I have one in my neighborhood... no problems.
Three Mile Island has had no problems with home values or appreciation.
http://www.jstor..../3146017
Does anyone else find it odd that the UN deadline for reducing CO2 emissions was 2000, then was moved to 2015, and now this report says we have decades? Of course the US must begin immediately while even larger coal economies can continue emissions for decades...
Coal is clean? What ever gave you that idea?
What regulations?
The real problem is that business wants the taxpayers to assume liability for the risks entailed.