Three researchers at Cornell University say a controversial study, conducted by their colleagues and stating that shale gas activities posed a more serious threat to global warming than coal, contains serious flaws and should be revisited.

Robert Howarth -- an ecology and biology professor at Cornell -- created a stir in the industry when he and two associates asserted that natural gas drilling and production in shale plays leaked more methane (CH4) than conventional wells and had more of an impact on global warming than carbon dioxide (CO2) released from coal (see NGI, April 18).

"Our review of their own sources finds no evidence that gas is being vented directly into the atmosphere at rates that could justify their conclusions," Cornell researchers Larry Brown, Lawrence Cathles and Andrew Hunter said in a short commentary over the Howarth study. "In contrast, their sources make clear that there are effective technologies to reduce methane emissions to the point they are an insignificant addition to methane's greenhouse combustion footprint, if indeed this is not already the case."

Brown and Cathles are earth science professors at Cornell while Hunter is a lecturer in chemical and biomolecular engineering at the school. Milton Taam, president of Electric Software Inc. of Berkshire, NY, also contributed to the repudiation of the Howarth report.

The four-page short commentary was released on Oct. 4, but a longer version will reportedly be published this month in the peer-reviewed journal Climatic Change Letters, which published the report by Howarth and his associates -- civil and environmental engineering professor Anthony Ingraffea and research aide Renee Santoro -- in its May issue.

"[We decided to pursue] a serious response to Howarth's claims, which we think are extreme," Cathles told NGI. "He's picked the embers to make an argument, and it's not a reasonable argument in the sense that it's not balanced."

Brown, Cathles, Hunter and Taam said the Howarth study erred because it didn't compare coal and natural gas in terms of how much electricity they can generate individually; leaked CH4 figures were improperly converted to their CO2 equivalents; and the study assumed "implausibly high" -- 1.9% of total production -- CH4 leakage rates from natural gas wells during various activities and provided no evidence to back up its claims.

Subsequent studies conducted by the Worldwatch Institute and Deutsche Bank Climate Change Advisors; IHS Cambridge Energy Research Associates; Carnegie Mellon University; Wood Mackenzie; the U.S. Environmental Protection Agency; and the gas-friendly American Clean Skies Foundation criticized the Howarth study for overstating CH4 emissions and said natural gas has fewer GHG emissions than coal (see NGI, May 16; April 25). Clean transportation advocate T. Boone Pickens also took issue with the Howarth report, but comments by Ingraffea have been used by Josh Fox, director of the anti-drilling film Gasland.

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