On Shale Gas, Warming and Whiplash One example is "On Plankton, Warming and Whiplash." Here we go again. This time, the issue is the hydraulic fracturing of shale and similar rock to extract natural gas (and oil, as well). This technique, widely known as fracking, has raised environmental concerns while opening a vast new resource that is reshaping energy menus from the United States to China. Newly published research led by Cornell University scientists challenges the core calculations and conclusions of a paper by another Cornell researcher, Robert Howarth, that became a potent talking point for opponents of hydraulic fracturing last year. Here's a link to the new paper, which was just published in Climatic Change. The Howarth paper, "Methane and the greenhouse-gas footprint of natural gas from shale formations," had estimated that leakage of gas from hydraulic fracturing operations (given that natural gas is mainly methane, a potent heat-trapping substance) and other factors made the climate impact of gas from such wells substantially worse than that of coal, measured per unit of energy. The abstract was bluntly worded: Compared to coal, the [climate] footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years. That finding cut against the long-established estimate that the greenhouse impact of natural gas was roughly half that of coal. It is this property of natural gas that long made many climate and energy analysts see a shift from coal to gas in electricity generation as a big, cheap and quick early step on the long road to curbing global warming. Howarth acknowledged, behind the headlines, that his conclusions were based on limited data. But opponents of hydraulic fracturing spun the study as proving that gas was no "bridge" to a climate-friendly global energy mix. Most news coverage of the Howarth paper played the debate over the findings as a crusading scientist (Howarth is a staunch foe of hydraulic fracturing in the Northeast) being challenged by the gas industry, when there were concerns expressed by other climate researchers at the time. Last year, Howarth's findings were questioned by researchers at the National Energy Technology Laboratory, as well. The gas industry, focused mainly on the documentary "Gasland," had to open a new Howarth front in its failing public relations campaign. Howarth's prime conclusion is now directly challenged in the new paper. Here's the keystone line from the abstract: Using more reasonable leakage rates and bases of comparison, shale gas has a [greenhouse gas] footprint that is half and perhaps a third that of coal. Setting aside the fights between environmentalists and industry, the picture emerging in the science is of an initial assertion in an area with inadequate data (largely because of the industry's proprietary bent) that is - unsurprisingly - being challenged. I encourage you to look back at Gavin Schmidt's "Fracking Methane" post from last year at Realclimate, which I feel nailed the nuances. I hope he will take a look at the new work, too. Unfortunately, when research on tough questions sits under the microscope because of its relevancy to policy fights, the impact on the public can be a severe case of whiplash. Journalists and campaigners succumbing to "single-study syndrome" in search of a hot front-page headline or debating point threaten to alienate readers seeking some sense of reality. Here's the abstract from the new paper, by Lawrence M. Cathles, Larry Brown, Milton Taam and Andrew Hunter (GHG stands for greenhouse gas): Natural gas is widely considered to be an environmentally cleaner fuel than coal because it does not produce detrimental by-products such as sulfur, mercury, ash and particulates and because it provides twice the energy per unit of weight with half the carbon footprint during combustion. These points are not in dispute. However, in their recent publication in Climatic Change Letters, Howarth et al. (2011) report that their life-cycle evaluation of shale gas drilling suggests that shale gas has a larger GHG footprint than coal and that this larger footprint "undercuts the logic of its use as a bridging fuel over the coming decades." We argue here that their analysis is seriously flawed in that they significantly overestimate the fugitive emissions associated with unconventional gas extraction, undervalue the contribution of "green technologies" to reducing those emissions to a level approaching that of conventional gas, base their comparison between gas and coal on heat rather than electricity generation (almost the sole use of coal), and assume a time interval over which to compute the relative climate impact of gas compared to coal that does not capture the contrast between the long residence time of CO2 and the short residence time of methane in the atmosphere. High leakage rates, a short methane GWP, and comparison in terms of heat content are the inappropriate bases upon which Howarth et al. ground their claim that gas could be twice as bad as coal in its greenhouse impact. Using more reasonable leakage rates and bases of comparison, shale gas has a GHG footprint that is half and perhaps a third that of coal. I reached out to Howarth today (when I asked his views on an early version of Cathles et al paper, he'd told me he had prepared a formal reply that was to be published in the journal along with the new work. There was some kind of logistical glitch, he said. In the meantime, the journal editors gave him clearance to offer this short reaction for Dot Earth: In April 2011, my colleagues Tony Ingraffea, Renee Santoro, and I published the first comprehensive analysis of greenhouse gas (GHG) emissions from shale gas obtained by hydraulic fracturing, with a focus on methane emissions, in the journal Climatic Change Letters. Our analysis was challenged by Cathles et al. We were invited by the journal to write a reply, with the understanding that the criticism of Cathles et al. and our reply would be published simultaneously early this year. Unfortunately, a mistake by the publisher apparently resulted in the premature publication of the Cathles et al. piece earlier today. We are still finalizing our reply, but we fully expect to have a reply finished and ready for publication within a few weeks at most, with publication on line following within 1-2 months after that. We stand by our approach and findings published last April, and find little of merit in the criticisms by Cathles and colleagues. The latest EPA estimate for methane emissions from shale gas falls within the range of our estimates but not those of Cathles et al, which are substantially lower. Cathles et al. believe the focus should be just on electricity generation, and the global warming potential of methane should be considered only on a 100-year time scale. Our analysis covered both electricity (30% of US usage) and heat generation (the largest usage), and we evaluated both 20- and 100-year integrated time frames for methane. Both time frames are important, but the decadal scale is critical, given the urgent need to avoid climate-system tipping points. We also used the latest available estimates for the global warming potential of methane, while Cathles relied on older and lower values. Using all available information and the latest climate science, we conclude that for most uses, the GHG footprint of shale gas is greater than that of other fossil fuels on time scales of up to 100 years. When used to generate electricity, the shale-gas footprint is still significantly greater than that of coal at decadal time scales but is less at the century scale. We reiterate our conclusion from our April 2011 paper that shale gas is not a suitable bridge fuel for the 21st Century.