Climate Policy: Is the Global Methane Pledge the Most Effective Strategy to Address Climate Change?
The Climate and Clean Air Coalition launched the Global Methane Pledge in November 2021. Over 100 countries committed to a global target to reduce global methane emissions by at least 30 percent from 2020 levels by 2030. According to the pledge, reducing methane is the “single most effective” strategy to limit global warming to the 1.5-degree Celsius threshold (Global Methane Pledge, n.d.).
However, not everyone agrees with prioritizing methane reductions in the race to mitigate climate change. John Lynch, an environmental scientist with the University of Oxford, describes prioritizing methane reductions over reducing CO2 emissions as a “fatal distraction” (Lynch J., 2022). So, is The Methane Pledge a silver bullet for addressing climate change or a strategic misstep? The answer, like climate change itself, is complicated.
Why methane is important
Methane (CH4) is one of four primary greenhouse gases (GHGs). Other GHGs include Carbon Dioxide (CO2), Nitrous Oxide (N2O), and fluorinated gases or HFCs (EPA, n.d.).
Methane is the second most prevalent of GHGs. About 11 percent of total U.S. GHG emissions are methane. (EPA, n.d.) Anthropogenic, or human-caused, sources of methane include:
· Production and transport of fossil fuels such as coal, natural gas, and oil
· Livestock and other agricultural practices
· Decay of organic waste in municipal solid waste landfills
· Land use
The Global Warming Potential (GWP) index, developed by the Intergovernmental Panel on Climate Change (IPCC), is used to measure GHGs emissions. The current GWP100 model establishes the warming equivalent of a non-CO2 GHG to units of CO2 over 100 years. Using GWP100, methane currently has 28 times the GWP as CO2 over 100 years (EPA, n.d.). The problem with the GWP100 methodology is that methane is a short-lived climate pollutant (SLCP) (Center for Climate and Energy Solutions, 2022). It only persists in the atmosphere for about 12 years. CO2 stays in the atmosphere for nearly 1000 years, by comparison. The 28x intensity of warming from methane and the short window to realize the effects of mitigation are key to strategies such as The Global Methane Pledge.
The “silver bullet” promise of methane
From a policy perspective, reducing methane makes a lot of sense. The strategy could result in a relatively quick win by reducing warming within decades, not centuries. Further, the technology and tools to plug leaking gas wells and recover and use vented methane from oil and gas wells and landfills already exist (Dixon, F., 2021; Van Dingenen et al., 2009; Avnery et al., 2011). Food waste can be reduced at the consumer level and diverted from landfills through programs that recover usable food from restaurants and manufacturers for donations. City-level policies can ban organic waste from landfills and establish composting programs.
Reducing methane emissions would also reduce ozone. As methane breaks down in the atmosphere, it produces ozone and water vapor, both GHGs. Ozone in the lower layer of the atmosphere, or troposphere, negatively impacts human health and crop yields.
The Climate and Clean Air Coalition (CCAC) and the United Nations Environment Programme (UNEP) conducted a cost-benefit analysis of methane reduction. Mitigating methane would cost an average of $600 per ton while delivering an estimated $470 billion in benefits per year, based on a 45% reduction in methane emissions within the next decade. The benefits include avoided deaths and hospital visits from cardiovascular and respiratory disease, avoided crop losses, and fewer work hours lost to extreme heat (CCAP and UNEP, 2021).
Given the strong business case to reduce methane emissions, how could scientists such as Lynch view the strategy as a “fatal distraction”? Lynch’s primary concern is that policymakers will focus on the quick and lower-cost win of reducing methane emissions instead of addressing the long-term threat from CO2. Lynch also conducted an analysis of methane as an SLCP versus CO2 emissions, which accumulate and continue to warm the climate for millennia (Lynch, Cain, et al., 2020).
Measuring the climate impact of methane versus CO2
The short-term opportunity with methane can seem more compelling when it is measured as an SLCP instead of a CO2 equivalent over a 100-year horizon. One such methodology under review is GWP*. GWP* measures GHGs other than methane consistently with GWP100. These GHGs, including CO2, N2O, and HFCs, are stock gases. Continued emissions add cumulatively to the atmospheric stock, increasing temperatures indefinitely if emissions continue. The temperature increases then remain fixed for centuries after emissions cease without removal (Lynch, Cain, et al., 2020).
The GWP* methodology treats historic, sustained methane emissions as a stock gas, a one-time release of CO2, which increases warming. New or increased methane emissions are calculated separately under GWP* with a 20-year warming effect four times greater than the 28 times equivalent of CO2 (CO2-e) used in the GWP100 methodology. There is some debate that use of the GWP* methodology would allow operations such as the gas and oil sector and livestock production to claim carbon neutrality without significant reductions in methane emissions (Boren, 2022). However, if GWP* proves to be a more accurate measurement for SLCPs like methane, then policies for methane reduction should be adjusted, rather than using inaccurate science. Policy shifts could include achieving a “beyond zero” or methane negative goal that fully leverages the short-term cooling effect of reducing methane.
Measuring the impact of increasing methane emissions is especially critical. According to NOAA climate data, atmospheric methane levels in 2021 showed the most significant annual increase recorded since systematic measurements began in 1983. (NOAA, 2022).
Source: National Oceanographic and Atmospheric Association
Current atmospheric methane levels are 162% greater than pre-industrial levels and 15% higher than measurements from 1984–2006. When you consider the dramatic, short-term warming effect of methane with GWP* and record increases in atmospheric methane, strategies like the Methane Pledge make a lot of sense.
However, the drawback to a methane-only drawdown is that same short-term gain. Once methane emissions stop increasing, within decades, as much methane will leave the atmosphere as the emissions.
So, which strategy is best, a short-term gain of reducing methane emissions by 30% to avoid a 0.2˚C temperature increase by 2050 (Global Methane Pledge, n.d.), or reducing CO2 emissions to prevent the catastrophic climate change outcomes predicted in the future?
Comparing long-term and short-term strategies with data modeling
In their Environmental Research letter, Lynch et al. modeled the concentration, temperature change, and forcing effects of reducing methane and CO2 emissions to zero over 50 years.
As you can see, the concentration, forcing, and warming effect of CO2 continues to increase after reducing emissions to zero. The CO2 graphs illustrate why long-term climate change mitigation strategies must include carbon sequestration or removal, not just reducing emissions.
The concentration, forcing, and warming effect of methane, however, reduce along a similar curve as the emissions reduction. This curve illustrates the immediate, short-term impact of methane reductions. The dotted line in the methane forcing graph demonstrates the forcing effect of methane alone. As methane breaks down in the atmosphere, it produces ozone and water vapor, increasing the climate forcing by 1.65x. The solid line shows this cumulative forcing in the graph.
Lynch et al. also modeled scenarios which begin with constant CH4 and CO2 emissions, then stopping one gas at 50 years and the other at 100 years (gold is CO2 first, and pink is methane first), or stopping ‘both early’ (both at 50 years) or ‘both late’ (both at 100 years). The black line indicates “Business as Usual.” Note the key differences in the outcomes for stopping either methane first or CO2 first, represented by the colored dashed lines. In the GWP* model, stopping CO2 first results in less warming in the long term than ceasing methane emissions first.
Based on these scenarios, the best outcome for warming is not an either/or decision. “Both early” reduction of CO2 and methane emissions is the path with the least warming, whether it is measured with GWP* or GWP100. The “both early” path is the only option to limit global warming to near the 1.5 degree threshold.
Silver bullets and false dilemmas
Based on the data and the co-benefits of methane emissions reduction, whether to focus climate strategies on reducing methane or CO2 is a false dilemma. Reducing methane emissions may not be the single most effective lever we have to address climate change. It is a crucial, short-term lever that can save lives and reduce warming in the short-term while we reduce CO2 emissions. To Lynch’s point in his essay on Bulletin of the Atomic Scientists, prioritizing methane emissions reduction over reducing CO2 emissions has long-term repercussions. We must do both. The real dilemma is if climate action gets derailed when solving such a complex issue is oversimplified.
Organizations often present a solution as a silver bullet or a “single most effective” action. “Plant More Trees!” has been one rallying cry behind programs and campaigns to plant trillions of trees, only to learn that rebuilding ecosystems, many of which include trees, is more effective and resilient (Einhorn, C., 2021). As we plant the right trees in the right place to sequester carbon, we must not miss the forest of solutions available to mitigate climate change, including restoration of grasslands and other ecosystems (Travis, 2021).
Nature-based solutions, appropriately implemented, offer the potential to drawdown up to 30-to-50% of GHG emissions (Seddon, N., Chausson, A. et al., 2020). These solutions are relatively low cost compared to current carbon capture technology, address biodiversity loss, and provide ecosystem benefits such as clean air and water, erosion control, flood and storm protection, and food (Ibid). However, planting a trillion trees and restoring ecosystems will not be enough. Limiting warming to even 2˚C is impossible without emissions reduction and potentially a viable carbon capture technology in the future to close the gap (Ibid).
Perhaps the most debated false dilemma is the tradeoff between economic growth or addressing climate change. This false dilemma treats addressing climate change as optional, ignoring the potential economic damage from inaction (Kormann, C. 2019). A study by Stanford University researchers calculated that global benefits of holding temperature increases to 1.5 degrees in the tens of trillions of dollars. The potential benefit is more than 30 times greater than the most recent estimates of costs to achieve a 1.5 degrees goal (Burke, M., Davis, W.M. and Diffenbaugh, N.S., 2018).
Most of all, false dilemmas and “silver bullets” detract from the findings of the IPCC’s Sixth Assessment Report: we need many actions across all sectors, stakeholders, regions, and types of GHGs to limit warming to 2˚C (IPCC, 2022). We need to reduce emissions and remove CO2. And we need to start immediately.
Works Cited
Global Methane Pledge. (n.d.). The Global Methane Pledge. https://www.globalmethanepledge.org/
Lynch, J. (2022, February 22). Fatal distraction: the problem with the methane pledge. Bulletin of the Atomic Scientists.https://thebulletin.org/2022/02/fatal-distraction-the-problem-with-the-methane-pledge/
EPA. (n.d.). Overview of Greenhouse Gases. EPA.gov. https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane
EPA. (n.d.). Understanding Global Warming Potentials. EPA.gov. https://www.epa.gov/ghgemissions/understanding-global-warming-potentials
Center for Climate and Energy Solutions. (2022, February 22). Short-lived Climate Pollutants.
https://www.c2es.org/content/short-lived-climate-pollutants/
Dixon, F. (2021, May 13). Why we must reduce methane emissions now to solve the climate crisis. Stockholm Environment Institute. https://www.sei.org/featured/why-we-must-reduce-methane-emissions-now-to-solve-the-climate-crisis/
Van Dingenen, R., Raes, F., Krol, M.C., Emberson, L. and Cofala, J. (2009) The global impact of O3 on agricultural crop yields under current and future air quality legislation. Atmos. Environ. 43, 604–618.
Avnery, S., Mauzerall, D.L., Liu, J. and Horowitz, L.W. (2011) Global crop yield reductions due to surface ozone exposure: 1. Year 2000 crop production losses and economic damage. Atmos. Environ. 45, 2284–2296.
Climate and Clean Air Coalition & United Nations Environment Programme. (2021). Global Methane Assessment: Benefits and Costs of Mitigating Methane. https://www.ccacoalition.org/en/resources/global-methane-assessment-full-report
Lynch, J., Cain, M., Pierrehumbert, R., & Allen, M. (2020). Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants. Environmental Research Letters, 15(4), 044023. https://doi.org/10.1088/1748-9326/ab6d7e
Boren, Z. (2022, June 21). How the beef industry is trying to change the maths of climate change. Unearthed. Retrieved October 6, 2022, from https://unearthed.greenpeace.org/2022/03/09/global-warming-potential-star-methane-agriculture-net-zero/
National Oceanic and Atmospheric Administration. Increase in atmospheric methane set another record during 2021. (2022, April 7). NOAA. https://www.noaa.gov/news-release/increase-in-atmospheric-methane-set-another-record-during-2021
Einhorn, C. (2022, March 21). Tree Planting Is Booming. Here’s How That Could Help, or Harm, the Planet. The New York Times. https://www.nytimes.com/2022/03/14/climate/tree-planting-reforestation-climate.html
Travis, K. (2021, July 14). Why planting tons of trees isn’t enough to solve climate change. Science News. https://www.sciencenews.org/article/planting-trees-climate-change-carbon-capture-deforestation
Seddon, N., Chausson, A., Berry, P., Girardin, C. A. J., Smith, A., & Turner, B. (2020). Understanding the value and limits of nature-based solutions to climate change and other global challenges. Philosophical Transactions of the Royal Society B: Biological Sciences, 375(1794), 20190120. https://doi.org/10.1098/rstb.2019.0120
Kormann, C. (2019, February 4). The False Choice Between Economic Growth and Combatting Climate Change. The New Yorker. https://www.newyorker.com/news/news-desk/the-false-choice-between-economic-growth-and-combatting-climate-change
Burke, M., Davis, W.M. & Diffenbaugh, N.S. Large potential reduction in economic damages under UN mitigation targets. Nature 557, 549–553 (2018). https://doi.org/10.1038/s41586-018-0071-9
IPCC, 2022. Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926
