Robert Howarth is a biogeochemist and environmental scientist and the David R. Atkinson Professor of Ecology and Environmental Biology at Cornell University, New York, USA. In his own words “Our lab works broadly on biogeochemistry and aquatic ecosystem science. Specific topics include global and regional nitrogen and phosphorus cycles; environmental consequences of biofuels; role of trace gases in global warming and climate disruption; life-cycle analysis for greenhouse-gas footprint of energy technologies; influence of land-use, management practices, and climate change on nutrient fluxes from the landscape; atmospheric deposition of nitrogen onto the landscape; controls and consequences of eutrophication in estuaries; biotic, physical, and geochemical controls on nitrogen fixation; and environmental management and the effects of pollutants on aquatic ecosystems” (see: http://ecologyandevolution.cornell.edu/people/faculty/robert-howarth.cfm ).
Professor Robert Howarth et al (2012) on the unsuitability of shale gas a s bridge fuel (2012): “Abstract. In April 2011, we published the first comprehensive analysis of greenhouse gas (GHG) emissions from shale gas obtained by hydraulic fracturing, with a focus on methane emissions. Our analysis was challenged by Cathles et al. (2012). Here, we respond to those criticisms. We stand by our approach and findings. 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. 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” and the conclusion “We believe the preponderance of evidence indicates shale gas has a larger GHG footprint than conventional gas, considered over any time scale. The GHG footprint of shale gas also exceeds that of oil or coal when considered at decadal time scales, no matter how the gas is used (Howarth et al. 2011; Hughes 2011a, b; Wigley et al. 2011). Considered over the century scale, and when used to generate electricity, many studies conclude that shale gas has a smaller GHG footprint than coal (Wigley 2011; Hughes 2011b; Hultman et al. 2011), although some of these studies biased their result by using a low estimate for GWP and/or low estimates for methane emission (Jiang et al. 2011; Skone et al. 2011; Burnham et al. 2011). However, the GHG footprint of shale gas is similar to that of oil or coal at the century time scale, when used for other than electricity generation. We stand by the conclusion of Howarth et al. (2011): “The large GHG footprint of shale gas undercuts the logic of its use as a bridging fuel over coming decades, if the goal is to reduce global warming.” [1].
Robert Howarth (41-Nobel-Laureate Cornell University), Dr Drew Shindell (NASA Goddard Space Institute) , Renee Santoro (41-Nobel-Laureate Cornell University), Anthony Ingraffea (41-Nobel-Laureate Cornell University), Nathan Phillips (7-Nobel-Laureate Boston University) and Amy Townsend-Small (University of Cincinatti), “Methane emissions from natural gas systems” (a background paper prepared for the National Climate Assessment 2012): “Methane [the major component of natural gas] is the second largest contributor to human-caused global warming after carbon dioxide … For the 20-year time frame, Shindell et al. (2009) provide a mean estimate of 105 for the global warming potential . Using this value , Howarth et al. (2012) calculated that methane contributes 44% of the entire GHG inventory of the U.S., including carbon dioxide and all other gases from all human activities. Hence, while methane is only causing about 1/5 of the century –scale warming due to U.S. emissions, it is responsible for nearly half of the warming impact of current U.S. emissions over the next 20 years. At this time scale, the methane emissions from natural gas systems contribute 17% of the entire GHG inventory of the U.S,, for all gases from all sources, We repeat that these estimates may be low, and that the gradual replacement of conventional natural gas by shale gas is predicted too increase these methane fluxes by 40% to 60% or more (Howarth et al, 2012)”. [2].
[1]. Robert W. Howarth, Renee Santoro, Anthony Ingraffea , “Venting and leaking of methane from shake gas development: a response to Cathles et al.”, Climatic Change, July 2012, Volume 113, Issue 2, pp 537-549: http://link.springer.com/article/10.1007%2Fs10584-012-0401-0 and http://link.springer.com/article/10.1007%2Fs10584-012-0401-0/fulltext.html .
[2]. Robert Howarth, Dr Drew Shindell, Renee Santoro, Anthony Ingraffea, Nathan Phillips, and Amy Townsend-Small, “Methane emissions from natural gas systems” (a background paper prepared for the National Climate Assessment, reference number 2011- 0003; February25 2012: http://www.eeb.cornell.edu/howarth/Howarth%20et%20al.%20--%20National%20Climate%20Assessment.pdf ).
Howarth, R. W. and A. Ingraffea. 2011. Should fracking stop? Yes, it is too high risk. Nature 477:271-273.
Howarth, R. W., R. Santoro, and A. Ingraffea. 2011. Methane and the greenhouse gas footprint of natural gas from shale formations. Climatic Change Letters 106(4):679-690, DOI:10.1007/s10584-011-0061-5 .