Coal Supply May Be Vastly Overestimated

May 11, 2009 -- Forget peak oil -- a series of new estimates of the world's coal supply suggests reserves may be vastly overestimated, and if the planet isn't running on a majority of alternative energies within the next few decades, we could be facing an unprecedented global energy crisis.

On the flip side, a dwindling supply of coal could also throw the breaks on global warming, some argue.

Common knowledge about coal is that major producing nations like China, the United States and Australia, have enough to last hundreds of years, far beyond the reach of oil, which may already be in its twilight years. But worldwide coal production could plateau as early as 2025, according to one new estimate, and a growing group of scientists are concerned that fossil fuel supplies may begin dwindling by mid-century.

Last year, David Rutledge of the California Institute of Technology analyzed the coal production patterns of five regions around the world -- eastern Pennsylvania, France, Germany's Ruhr Valley, the United Kingdom and Japan -- each of which was producing at less than a tenth of its peak levels.

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He found that each of the depleted regions followed a rough bell curve of production; initial production was followed by a steep ramp-up, a plateau near peak levels, and then a consistent decline.

When he applied the same formula to coal data from around the world, the results were startling: the United Nations Intergovernmental Panel on Climate Change's maximum estimate for extractable coal is about 3,400 billion tons. Rutledge's calculations suggest just 666 billion tons.

The problem with the IPCC estimate is that it lumps coal "reserves" which are easy to mine with coal "resources," which may be impossible to mine. And Rutledge's study shows that, historically, national governments in the five regions have overestimated their reserves by a factor of four on average.

"These appraisals are large-scale issues," he said. "But they're done by governments. What's the incentive for governments not to give a number that is too high?"

James Murray of the University of Washington agrees. In a talk being presented later this month at the American Geophysical Union Joint Assembly, he plans to call for a re-evaluation of IPCC emissions scenarios, all 40 of which overstate humanity's ability to emit the greenhouse gas carbon dioxide, according to Rutledge's numbers.