Fracking and climate change

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This article is part of the FrackSwarm coverage of fracking.
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Natural gas is often considered cleaner than coal because it releases about half as much carbon dioxide when it is burned in power plants, and fewer pollutants per unit of energy. Natural gas, however, is composed primarily of methane, which may leak into the atmosphere during and after production ("upstream" emissions are those produced at the well site, "midstream" from processing, and "downstream" from gas storage, transmission, and distribution. Gas wells that lose their structural integrity may also leak methane.)


The 2013 IPCC report increased the "global warming potential" of methane to 28 over 100 years and 84 over 20 years, as compared to an equivalent mass of carbon dioxide. If carbon feedbacks from methane emissions are taken into account, then the GWP for methane increases to 34 over 100 years and 86 over 20 years (Chapter 8, Table 8.7 on page 8-58).

Some argue that natural gas is a good "bridge fuel" to carbon-free energies because it can be used in peaker plants to balance out the intermittency of renewables like solar and wind until they reach larger capacity.[1] Others argue that methane leakage makes gas a "gangplank to more warming and away from clean energy investments."[2]

U.S. methane emissions

According to the EIA, U.S. methane emissions from "natural gas systems" grew from 1990 to 2009 by 27 percent (39 million metric tons CO2 equivalent) due to increased natural gas use. The EIA states that all U.S. methane emissions in 2009 totaled 731 MMTCO2e.[3] There is disagreement, however, about the rate of gas production leakage, which affects total methane emission rates.

The Intersection Between Hydraulic Fracturing and Climate Change.

Methane leakage from oil/gas production

Various studies by academics, government, and industry have found that methane leakage can range from less than 1 percent to almost 12 percent[4] of the natural gas produced each year. The difference is attributed to the small amount of raw data available and variations in the way the data are interpreted.[5]

A paper published in October 2015 in Water Resources Research examined an area in New York above the Marcellus Shale formation. More than 30,000 wells burrow into the shale. The authors, Dr. James A. Montague and George F. Pinder, used a mathematical model to map the probability that new hydraulic fracturing would connect to a previously used oil and gas wells, create damage, and let methane seep. The probability was found to be ten percent or more.[6]

EPA reports

In 2011, the EPA estimated that 2.8 percent of gas produced from a well each year leaks (combining both conventional and unconventional wells)[5], doubling its previous estimate.[7]

The EPA asserts that methane accounts for 10% of climate change in 2013.[8]

Oil/gas companies and Devon Energy, in particular, criticized EPA for relying on what they said is a small, outdated sample with data gaps.[5] In May 2012 the American Petroleum Institute released a study which stated that the EPA’s greenhouse-gases inventory released in 2011 “substantially increased estimates of methane emissions from petroleum and natural-gas systems.”[9]

In April 2013, the EPA said tighter pollution controls instituted by the industry resulted in an average annual decrease of 41.6 million metric tons of methane emissions from 1990 through 2010 (more than 850 million metric tons overall) - a 20 percent reduction from previous estimates.[10] The agency now estimates that methane leaks from gas drilling amount to an average of 1.5% (others calculate about 1.65 percent) "based on industry guesses," as stated by the Christian Science Monitor. Critics argue the EPA has been under pressure by the gas industry concerning fracking regulations.[11]

2011 Cornell study

A 2011 study out of Cornell University found leakage of 2.2 to 3.9 percent of produced gas per well, and up to 8 percent.[5] The authors, Robert Howarth and Anthony Ingraffea, estimate that fracked wells leak 40 to 60 percent more methane than conventional natural gas wells. When water with its chemical load is forced down a well to break the shale, volumes of methane also flow back up the well at the same time and are released into the atmosphere before they can be captured for use. They argue that, within the next 20 years, methane will contribute 44 percent of the greenhouse gas load produced by the U.S. Of that portion, 17 percent will come from all natural gas operations.[12]

2012 NOAA et al studies

A 2012 NOAA study published in the Journal of Geophysical Research is considered by some as more authoritative than other estimates because scientists based it on actual measurements of leakage at Colorado gas fields in 2008 (although the findings cannot necessarily be generalized to other well sites). That study found that about 4 percent of the 202 billion cubic feet of gas produced that year may have leaked in the Denver-Julesburg Basin. NOAA's methods for calculating leakage - chemical analysis of the pollutants - have been challenged, most prominently by Michael Levi at the Council on Foreign Relations, who reworked the raw data of the NOAA study without the same assumptions and found leakage of 1.3 to 2.3 percent.[5]

In September 2012 researchers at the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado in Boulder reported preliminary results from a field study in the Uinta Basin of Utah suggesting methane leakage of up to 9% of total gas production, nearly double the cumulative loss rates estimated from industry data. The NOAA researchers collected their data in February 2012 as part of a broader analysis of air pollution in the Uinta Basin. The researchers used atmospheric modelling to calculate the level of methane emissions required to reach the recorded concentrations, and then compared that with industry data on gas production to obtain the percentage escaping into the atmosphere through venting and leaks.[13] The research was published in 2013, and reported a methane leakage rate of 6.2 to 11.7% in the Basin.[14]

New research is using atmospheric inversion models to filter out local methane emissions like agriculture. The preliminary studies suggest leakage of 6 percent or lower globally.[15]

2013 EDF study

In October 2013 the University of Texas, Austin, the Environmental Defense Fund, and nine major natural gas companies said that, in January 2013, the group will begin publishing raw data, collected at their drilling sites, and offer them for peer review.[5] The study, published in the Proceedings of the National Academy of Sciences (PNAS), was released in September 2013, and was based on methane emissions at 190 natural gas well production sites nationwide in 2012 (0.11% of wells nationwide), including 490 wells and 27 fracking flowback operations. The sites were provided by the oil and gas companies involved in the study, many of which had equipment installed that either captured or combusted methane emissions.

The study found that *upstream* natural gas drilling sites emit 0.42 percent of the gas produced, versus the EPA’s upstream estimate of 0.47 percent (2.3 million tonnes per year versus the 2011 EPA estimate of 2.5 million tonnes).[5] EDF found much lower emissions during well completion than the EPA, as emissions control equipment at the wells drastically reduced emissions during the process (required for new wells by 2015), but higher estimates during other phases of production.[16]

There was large variation among the wells: the scientists examined nine well pads that vented methane during completion. They noted that one well emitted seven times as much methane as an adjacent well ("super-emitter"), even though both were being drilled by the same company at the same time, right next to each other. The study also found that some well pads release large amounts of methane during “liquids unloading,” a process in which workers periodically clean a producing well and remove excess water. The worst pads emitted 190,000 standard cubic feet (scf) of methane, while the best emitted only 1,000 scf.[5] Physicians Scientists & Engineers for Healthy Energy (PSE) noted that it is unclear whether the 27 wells sampled in the study during flowback were shale, tight-sand, coalbed methane, or a combination of well types, which may account for some of the variation in emissions, and make it harder to generalize the findings to shale gas operations.[17]

According to Cornell University professor Anthony Ingraffea, the methane emissions control technology used at most of the sites included in the study (chosen by industry, which he said is a conflict of interest) are not used at most of the natural gas production sites nationwide, so EDF's study results are not representative of methane emissions at most wells. He also said the study sampled too few fracking sites for it to be statistically representative of nationwide fracking — only 27 of the more than 25,000 fracking operations that occurred in 2012.[18] Robert Howarth of Cornell said the study conflicts with non-industry sponsored NOAA studies finding much higher leakage rates at gas production sites, and at most could be seen as representative of best practices that should be employed at all sites. He added that the study reported a lot of flaring, which would increase methane emissions if it were simply vented (released).[19] MIT's Henry Jacoby said the great bulk of the problem is elsewhere, "downstream in the natural gas system," including poorly capped oil and gas wells no longer in production.[16]

Aside from the scientific disagreements, two critics of the study note that "The study had been viewed with skepticism before its release because 90 percent of the $2.3 million in funding came from nine energy companies, including Encana, Chevron and a subsidiary of ExxonMobil."[20] One author, Jennifer Miskimins, is currently the employee of a petroleum engineering firm, Barree & Associates, and has been since 2012. The firm offers a range of consulting services related to fracking.[21]

Harvard PNAS study

In November 2013, a study published in the Proceedings of the National Academy of Sciences (PNAS) found that the EPA's methane emissions inventory underestimates the methane releases nationwide by as much as 50 percent. The study took nearly 13,000 measurements directly from the atmosphere in 2007 and 2008, and concluded US methane emissions accounted for the equivalent of 33.4 million tonnes of carbon per year, compared with the EPA’s estimate of 22.1 million tonnes in 2008.

The discrepancy between the Harvard study and EPA's inventory is due to livestock and, predominantly, the oil and gas sector, according to co-author Marc Fischer of the Lawrence Berkeley National Laboratory: "Even if we made emissions from livestock several times higher than inventory estimates would suggest for the southwest, you still don't get enough to cover what's actually being observed. That's why it looks like oil and gas are likely responsible for a large part of the remainder." The scientists found that Texas and Oklahoma emitted about five times more methane than is currently assumed - an average of 3.7 terragrams of carbon in the form of methane every year, compared to the 0.75 terragrams of carbon reported in EDGAR (EDGAR is roughly similar to EPA's inventory).[22]

The study concludes that "These results cast doubt on the US EPA’s recent decision to downscale its estimate of national natural gas emissions by 25–30%."

Leakage from wells

In addition to methane leakage during the production process, gas and oil wells that lose their structural integrity also leak methane and other contaminants outside their casings and into the atmosphere and water wells. Multiple industry studies show that about 5 percent of all oil and gas wells leak immediately because of integrity issues, with increasing rates of leakage over time.[23]

Carbon emissions from natural gas

Gas vs coal

Compared to the average air emissions from coal-fired generation, natural gas produces half as much carbon dioxide (about a half ton of CO2 for every MWh of electricity produced), and less than a third as much nitrogen oxides and one percent as much sulfur oxides at the power plant.[24]

Global emissions

In 2010, 20% of global CO2 emissions (6.2 gigatonnes) from fuel combustion were produced from gas (another 43% was coal and 36% oil), 7.1% higher than in the previous year (IEA). The IEA projects emissions from gas will reach 9.2 GtCO2 in 2035.[25]

U.S. emissions

U.S. coal plants were responsible for almost 80 percent of electric sector CO2 emissions in 2011, while the share of emissions from natural gas is growing steadily, rising from 15 percent in 2008 to 19 percent in 2011 and up to 24 percent in 2012, according to the U.S. Energy Information Administration (EIA).[26]

Since January 1, 2012, industries that use natural gas (large oil and gas facilities, LNG terminals, chemical plants, and refineries) have proposed or obtained Clean Air Act permits that authorize a 91 million ton increase of carbon dioxide equivalents per year — as much as the output from twenty 500 megawatt coal-fired plants, according to the Environmental Integrity Project. This total does not include new emissions from proposed gas-fired power plants or drilling and transport. Not all the proposed permits have been approved.[27]

Gas flaring

A gas flare, alternatively known as a flare stack, is a gas combustion device used in industrial plants such as petroleum refineries, chemical plants, natural gas processing plants as well as at oil or gas production sites having oil wells, gas wells, offshore oil and gas rigs and landfills. In industrial plants, flare stacks are primarily used for burning off flammable gas released by pressure relief valves during unplanned over-pressuring of plant equipment.[28] Vast amounts of associated gas at oil drilling sites are also commonly flared as waste or unusable gas.[29]

Flaring emits carbon dioxide and is a significant source of CO2 emissions. Some 400 million tons of carbon dioxide are emitted annually in this way, amounting to about 1.2 per cent of the worldwide emissions of carbon dioxide, as estimated by the World Bank (2013).[30]

Global gas flaring crept up by 4.5 percent to around 140 billion cubic meters (bcm) in 2011, up from 134 bcm the previous year, and the first rise since 2008, according to preliminary data from the World Bank. The increase has been primarily attributed to the rise in tight oil exploration in North Dakota.[31]

In addition to methane, gas- and oil-suffused bedrock contains many toxic hydrocarbons, some of them volatile gases. As soon as a hole is drilled into the formations, the fugitive native gases can escape, including benzene.[32]

Proposed federal regulations

Global warming potential

The global warming potential of methane was estimated at 21 times that of carbon dioxide averaged over 100 years in the IPCC Second Assessment Report (1995), and the 21 figure is currently used for regulatory purposes in the U.S.,[33] although in 2013 the EPA proposed increasing the number to 25, in line with the 2007 IPCC estimate.[34]

Methane and air pollutants

The Environmental Protection Agency (EPA) is finalizing air pollution standards for natural-gas drilling. The standards were proposed in summer 2012 in response to complaints from citizens and environmental groups that gases escaping from the 13,000 wells drilled each year by fracking were causing health problems and widespread air pollution.[35]

The rules would require all new and any modified wells to use equipment to capture fumes that escape in the production and processing of natural gas. The fumes include methane, a potent GHG and the main component of natural gas, and volatile organic compounds, which contribute to ground-level ozone (smog). The regulations will also limit emissions from compressors, oil storage tanks and other oil-and-gas sector equipment. Complying with the mandates is projected to lower methane emissions by about 26 percent and toxic air emissions by 30 percent, according to the EPA. The rules are expected on April 17, 2012, due to a court-ordered deadline. The underlying emissions rules for gas drilling operations were last modified in 1985, and and applies only to leak detection at new and upgraded gas processing plants.[36][37]

The rules were issued on April 18, 2012, and will be fully effective in January 2015. The EPA said the new rule would reduce emissions of volatile organic compounds by 190,000 to 290,000 tons per year and toxic air pollutants by 12,000 to 20,000 tons a year, and would save the gas industry $11 million to $19 million a year because drillers would be able to capture and sell the methane that is currently being burned off, or flared.[35]

Carbon dioxide emissions

On March 27, 2012, the EPA released its new rule limiting CO2 emissions from future electricity generating plants in the U.S., which proposes that new plants emit no more than 454 kilograms of CO2 per megawatt‐hour. It would go into effect in 2013. Science concluded that the cap is unlikely to have much impact on power plants fueled by natural gas: "Nearly all gas-fired power plants built in the U.S. since 2005 would already meet the standard, according to EPA, as would typical gas plants on the drawing boards."[38] The proposed rules have been delayed for release until June 2015.[39]

In June 2013, Obama announced his proposed Climate Action Plan. The plan involves using EPA authority to regulate carbon emissions. Critics noted that the policy proposal could lead to increased fracking for natural gas, since gas releases less carbon than coal when burned, but leaks methane during the life-cycle of production. Obama stated that methane emissions should be limited.[40]

Various reports and studies have concluded that the reduced CO2 emissions at gas plants will be negated if methane leakage during the gas production life cycle is not minimized.[41][42][43][44]

On Sep 20, 2013, the EPA issued new CO2 rules separating coal and gas regulations. Newly built coal-fired power plants will have to keep carbon emissions below 1,100 pounds per megawatt hour—a level that will force new plants to have carbon capture and storage technology. Newly constructed natural-gas plants will be permitted to emit no more than 1,000 pounds of C02 per megawatt hour - essentially the level at which cleaner burning natural-gas plants currently perform.[45]

Areas of debate on methane emissions

Amount of leakage

In what they called the first comprehensive analysis of methane leakage from shale gas, Howarth et al. (2011) estimated a net methane loss of 3.6-­7.9% of the total production of an average shale gas well during its lifetime: 1.9% during well completion, 0.3-1.9% for routine venting and equipment leaks, 0.19% during processing, and 1.4-­3.6% during transport, storage, and distribution. The estimate range is 30-50% higher the fugitive methane emissions for conventional gas (1.7-­6%).[46]

The study has been criticized for relying on data from various estimates that are not peer-reviewed, including poorly maintained wells in Russia,[47] while Howarth et al (2012) responded that the study was based on best available data and has been corroborated by later studies.[48]

Critics also say gas companies have economic incentive to minimize leakage and venting,[47] while Howarth et al (2012) point to a 2011 EPA report suggesting gas has become so low-cost that "industry is more likely to use their funds for more profitable ventures than capturing and selling vented gas."[48] The 2013 EDF/industry study suggested upstream methane emissions are much lower at sites with pollution control equipment,[16] while Howarth (2013) argued the study was not representative of industry-wide practices, and conflict with non-industry sponsored NOAA studies finding much higher leakage rates at gas production sites.[19]

Global warming potential

After estimating shale gas leakage, Howarth et al (2011) then estimated the greenhouse gas (GHG) footprint of methane using its global-warming potential (GWP) - a relative measure of how much heat a greenhouse gas traps in the atmosphere. The GWP compares the amount of heat trapped by a certain mass of gas, like methane, to the amount of heat trapped by a similar mass of carbon dioxide.

On a mass-to-mass basis when compared to CO2, the researchers gave methane a global warming potential of 105 and 33 for the 20-­ and 100-­year horizons, based on a 2009 study in Science that they said accounts for "the latest information on methane interactions with other radiatively active materials in the atmosphere."[48] They then argued that on a 20-year basis, the GHG footprint of shale gas compared to coal is 20% to 100% larger.[46]

Howarth et al argue the 20-year timeline is appropriate because a 2011 UNEP/WMO report predicts that the lower bound for the setting off methane release in permafrost – a 1.5°C increase – "will occur within the next 18 years or even less if emissions of methane and other short-lived radiatively active substances such as black carbon are not better controlled, beginning immediately" (the UNEP/WMO report accounts for the interaction between methane with aerosols).[48]

Some climate scientists argue that a global temperature potential (GTP) is a better metric for comparing GHGs than the GWP. A GTP is the global average temperature response to a pulse emission in a climate model, instead of the radiative forcing (the difference of radiant energy received by the earth and energy radiated back to space - the GWP is defined as the ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas, usually CO2). The GTP for methane for 100 years is about 7. Along these lines, some climate scientists point to climate models suggesting that peak warming in response to GHG emissions depends on long-term, cumulative GHG emissions, rather than the rate of emissions, making the limitation of overall CO2 emissions the more important focus, given its longer lifetime than methane.[49]

The Howarth study (2011) has also been criticized for gas-to-coal comparisons on a per energy unit basis (heat) when gas plants are more efficient than coal plants, suggesting a per kWh comparison (electricity) is more appropriate.[47] Howarth et al (2012) argue that only 30% of gas in the US is used for electricity, and most is used for heat, making the heat comparison appropriate. They argue that "while generating electricity from natural gas has some efficiency gains over using coal, we are aware of no such advantage for natural gas over other fossil fuels for providing heat."[48]

Less sulfates, more warming

A 2011 National Center for Atmospheric Research study found that cutting worldwide coal burning by half and using natural gas instead would increase global temperatures over the next four decades by about one-tenth of a degree Fahrenheit. This is because of estimated methane leakage and less sulfate emissions: while coal produces more global-warming gas per unit of energy than natural gas, the sulfates released by coal block incoming solar radiation, with a temporary, slight cooling effect.[50]

A 2011 NASA study suggested that a decade-long lull in global warming may be due to large sulfur dioxide emissions from coal plants without pollution controls in Asia.[51]

Effect of gas on renewables

According to the International Energy Agency's WEO 2012, private and public investment in fossil fuel projects over the next quarter-century will outpace investment in renewable energy by a ratio of three to one, raising questions of how much growth of gas supplies takes away from investment in zero carbon sources, as opposed to bridging to them.

A 2013 CO2 Scorecard study concluded that, in 2011 and 2012, natural gas was already displacing the use of lower carbon hydropower, as well as nuclear power.[52]


  • Shakeb Afsah and Kendyl Salcito, Shale Gas: Killing Coal without Cutting CO2, CO2 Scorecard, Dec 02, 2013 - argues that the 2011-2012 CO2 savings from using natural gas over coal were negated by 1) the increased use of gas over zero-carbon nuclear and hydropower, and 2) the leakage rate of methane (EPA average leakage estimate of 1.5%).
  • Eric Larson, Natural Gas & Climate Change, Climate Central, May 2013 - examines greenhouse gas benefits of switching from coal to gas based on various methane leakage rates of 2%, 5%, and 8%. Found that, at an average annual conversion rate of electricity from coal to gas of 2.5 percent, the reductions at a 2 percent methane leak rate would be 29 percent by 2050, and a 5 percent leakage rate would have benefits of 12 percent by 2050. With an 8 percent leak rate, GHG emissions would be greater than with coal for more than 50 years before a benefit begins to be realized.
  • Reducing Upstream GHG Emissions from U.S. Natural Gas Systems, World Resources Institute, April 2013.
  • Michael Levi, Climate consequences of natural gas as a bridge fuel, Climatic Change, 2013 - finds that switching gas for coal can help stabilize CO2 emissions if the goal is 550 parts per million (CO2 in the atmosphere), but that both gas and coal must be phased out quickly to reach a goal of 450 ppm.
  • GHGRP 2011: Reported Data, EPA, released Feb. 2013. - The EPA's accounting of emissions that cause global warming from stationary sources found that emissions from drilling, including fracking, and leaks from transmission pipes totaled 225 million metric tons of carbon-dioxide equivalents during 2011, second only to power plants, which emitted 2,221 million metric tons of carbon dioxide in 2011.
  • Has US Shale Gas Reduced CO2 Emissions? Examining recent changes in emissions from the US power sector and traded fossil fuels, Tyndall Centre for Climate Change Research, October 2012 - compares drop in US CO2 emissions with increases in US coal exports. Concludes that more than half of the emissions avoided in the US power sector from natural gas may have been negated through coal exports (exports equivalent to 340 MtCO2 emissions elsewhere in the world, i.e. 52% of the 650 MtCO2 of potential emissions avoided within the US).
  • Ramón A. Alvareza, Stephen W. Pacalab, James J. Winebrakec, William L. Chameidesd, and Steven P. Hamburge, Greater focus needed on methane leakage from natural gas infrastructure, Proceedings of the National Academy of Sciences, February 2012 - introduces the idea of “technology warming potentials” (TWPs) to reveal “reveal time-dependent tradeoffs inherent in a choice between alternative technologies.” Using this approach, the potent warming effect of methane (CH4) emissions undercuts the value of fuel switching in the next few decades; the study finds that a big switch from coal to gas would only reduce TWP by about 25% over the first three decades—not the 50% drop in CO2 emissions often claimed. The conclusion is based on “EPA’s latest estimate of the amount of CH4 released because of leaks and venting in the natural gas network between production wells and the local distribution network” of 2.4%. Many experts believe the leakage rate is higher than 2.4% for fracking.
  • Nathan Myhrvold and Ken Caldeira, Greenhouse gases, climate change and the transition from coal to low-carbon electricity, Environmental Review Letters 7 014019, February 2012 - looked at switching from one terawatt of coal power plants to natural gas-or to solar panels, or wind, or nuclear, or other options. In the natural gas scenario, the study calculated a range of warming trajectories for warming 100 years from now, with temperatures 17 to 25 percent lower than they would be if the world stuck with coal. The cut in the warming trajectory was far sharper for a switch to energy sources with near-zero emissions—such as nuclear, wind, or solar energy. The reduction in the temperature increase was 57 to 81 percent, according to the study models.
  • Tom Wigley, Coal to gas: the influence of methane leakage, Climatic Change, 2011 - found that unless leakage rates for new methane can be kept below 2%, substituting gas for coal is not an effective means for reducing the magnitude of future climate change: "We consider a scenario where a fraction of coal usage is replaced by natural gas (i.e., methane, CH4) over a given time period, and where a percentage of the gas production is assumed to leak into the atmosphere. The additional CH4 from leakage adds to the radiative forcing of the climate system, offsetting the reduction in CO2 forcing that accompanies the transition from coal to gas."
  • David Hughes, Life Cycle Greenhouse Gas Emissions from Shale Gas Compared to Coal: An Analysis of Two Conflicting Studies, PCI, June 30, 2011.
  • Robert W. Howarth, Renee Santoro, and Anthony Ingraffea, Methane and the greenhouse-gas footprint of natural gas from shale formations: A letter, Climatic Change, March 2011 - estimates that as much as 8 percent of the methane in shale gas leaks out into the air during the lifetime of a hydraulic shale gas well, making it a higher greenhouse gas emitter than conventional gas, oil, or even coal. Argues that if there is leakage of 2.5% or more of methane, gas is worse than coal in terms of effect on climate.



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  49. Daniel P. Schrag, "Is shale gas good for climate change?" The American Academy of Arts and Sciences 141 (2), Spring 2012.
  50. Geoff Mohan, "Clean natural gas? Not so fast, study says" LA Times, Sep. 8, 2011.
  51. Adam Voiland, "Has Sulfate Pollution from Asia Masked a Decade of Warming?" NASA, July 6, 2011.
  52. Shakeb Afsah and Kendyl Salcito, "Shale Gas: Killing Coal without Cutting CO2," CO2 Scorecard, Dec 02, 2013.

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