Clare Baldwin, PlanetArk 19 Dec 08;
SAN FRANCISCO - Researchers and officials concerned about global warming have focused on oil usage, but scientists on Wednesday said liquefied coal could have a greater affect on global climate change.
Global warming scenarios are based on oil reserves, but those reserves will have less impact on global climate than the extent to which liquefied coal replaces oil and gas, scientists said at a meeting of the American Geophysical Union in San Francisco.
"Oil and gas by themselves don't have enough carbon to keep us in the dangerous zone for very long by themselves, but that's assuming we do something about coal," Pushker Kharecha, a researcher for the U.S. space agency NASA and Columbia University in New York.
Estimates vary, but coal is the most abundant fossil fuel, and countries like China and the United States are looking at liquefaction technology. Many industries in South Africa already use liquefied coal.
In 2007, Illinois Democratic Sen. Barack Obama and Kentucky Republican Jim Bunning introduced legislation that would set the stage for large-scale production of transportation fuels from coal. Bunning and president-elect Obama come from state with prodigious coal supplies.
Liquefied coal releases 40 percent more carbon dioxide than oil when burned, said Ken Caldeira, a scientist at the Carnegie Institution of Washington.
"Addressing the climate problem means addressing the coal problem," he said. "Whether there's a little more oil or a little less oil will change the details, but if we want to change the overall shape of the warming curve, it matters what we do with coal."
ELEVATED LEVELS OF CARBON DIOXIDE
Caldeira said his climate models show that if all oil used in the world is replaced with liquefied coal, global temperatures will rise 2 degrees Celsius (3.6 degrees Fahrenheit) by 2042, three years sooner than if oil remains a staple.
If oil is replaced with solar, wind, or nuclear power, temperatures will rise 11 years later.
Many scientists believe high levels of atmospheric carbon dioxide lead to warming and effects like melting glaciers, thawing permafrost, ocean acidification and latitudinal shifts in climate.
Current atmospheric carbon dioxide levels are 385 parts per million and rising at a rate of about 2 parts per million (ppm) year as a result of burning coal, oil, and gas, the researchers said.
The generally accepted threshold for atmospheric carbon dioxide is 450 ppm. But scientists today said that number should be 350 ppm.
Climate change is a slow process, Kharecha said, and the effects may take decades and centuries to show up.
"There are currently more than enough fossil fuels and coal to push us well past safe atmospheric CO2 levels," he said.
None of the models presented at the session included carbon dioxide emissions from unconventional fossil fuels like tar sands, methane hydrates or oil shale.
Representatives from the liquefied coal industry could not be immediately reached for comment. In February, Robert Kelly of DKRW Advanced Fuels, which is building a liquefied coal production facility in Wyoming, told Reuters, "liquefied coal could be a huge fuel source for the next 50 years if we do it responsibly." He said coal emissions could be safely captured and stored underground.
(Editing by Maggie Fox and Stacey Joyce)
Climate outcome 'hangs on coal'
Jonathan Amos, BBC News 19 Dec 08;
If growth in carbon dioxide emissions is to be constrained and even reversed then the world cannot afford a coal renaissance, scientists have said.
Some commentators have argued that falling reserves of oil and gas will automatically limit CO2's rise.
But at an American Geophysical Union meeting, researchers said reserves of coal dwarfed those of other fuels.
It was even possible oil's demise could trigger an acceleration in emissions through more coal use, they added.
"We can replace oil with liquid fuels derived from coal," said Ken Caldeira from the Carnegie Institution at Stanford University in California.
"But these liquid fuels emit even more carbon dioxide than oil, so the end of oil can mean an increase in coal and even more carbon dioxide emissions to the atmosphere, and even more rapid onset of dangerous climate change."
Professor Caldeira's group has used climate and carbon cycle models to look at how future emissions and temperature projections would be altered by different fuel strategies.
The team tried to work out the maximum effects that would arise from replacing oil either entirely with coal-based liquid substitutes or entirely with renewable energy sources.
The assessment found that if coal-derived liquids are adopted, the Earth would achieve a 2C rise in temperature from pre-industrial times (a figure sometimes quoted as being a desirable ceiling to stay beneath in order to avoid "dangerous climate change") by 2042. This is three years faster than a business as usual future with oil.
If the renewables strategy is adopted, the 2C figure is not reached until 2056.
"Clearly, to address the climate issue we have to address the coal issue," Professor Caldeira told BBC News.
His assessment was shared by Pushker Kharecha from Nasa's Goddard Institute for Space Studies (Giss).
"We cannot move into things like coal-to-liquids and unconventional fossil fuels such as methane hydrates, tar sands, oil shale and so forth," he said.
"If they become large-scale substitutes for oil and gas, that would worsen things because they are much dirtier than oil and gas because they produce more emissions per unit energy delivered."
Reserve judgement
Dr Kharecha presented details of recent research from the US, UK and France looking at the feasibility of not only constraining the growth of CO2 emissions but actually reducing its concentration in the atmosphere to 350 parts per million by volume (it is currently up at about 385ppmv).
The group found it was possible, but only with a prompt moratorium on new coal use that does not capture CO2, and a phase out of existing coal emissions by 2030.
Reforestation together with improved agricultural practices could help draw down CO2.
"Efficiency and conservation have huge potential to offset emissions in the near term," Dr Kharecha told BBC News.
"And then in the mid-term and long-term we can focus on moving to alternatives such as renewable energies, and possibly a balanced look at nuclear because it does provide many benefits in addition to the numerous problems that it poses."
A new analysis presented here puts the total available global coal reserves at 662 billion tonnes.
The figure is substantially lower than the ones used in assessments by the Intergovernmental Panel on Climate Change (IPCC) to gauge possible future emissions scenarios.
"This is a radically different number from what is conventionally assumed," said Professor David Rutledge from the California Institute of Technology, who led the analysis.
"The IPCC assumes that about five times as much coal is available for burning."
But the scientists at this meeting said that if burnt, even this smaller amount of coal would radically alter the climate unless all the emissions were captured and stored.
"There is far more than enough currently useable coal and other fossil fuels to push us past the threshold beyond which we would not want to go with the climate," Dr Kharecha said.
