Accounting For Methane: A Look at the Evolving Greenhouse Gas Emissions Landscape

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Accounting For Methane: A Look at the Evolving Greenhouse Gas Emissions Landscape

At Stok, we value diverse perspectives and the opportunity to amplify the voices of the next generation of climate professionals. This blog post was co-authored by Stok’s Director of Carbon Services Colette Crouse and students in her Masters of the Environment Carbon Accounting & Management course at the University of Colorado, Boulder: Rebecca Billingsley, Andrea Green, and Kenny Prior (see bios below).

Mitigating emissions and removing carbon dioxide (CO2) from the atmosphere have long been the focus of climate action efforts; however, little attention has been paid to another greenhouse gas with an immediate and potent impact on climate change: methane (CH4). Discussion around the climate change contribution of short-lived climate pollutants (SLCPs) such as methane, and the importance of prioritizing SLCPs in decarbonization efforts has become an increasing topic of discussion among climate scientists and companies alike.


The climactic impact of methane emissions are underrepresented in current climate models and climate action plans. While methane has an atmospheric lifetime of 12 years, it has a much higher ability to absorb energy while in the atmosphere as compared to CO2,. Historically, so-called “global warming potentials” (GWPs) have been quantified through observations of warming over a 100-year period (GWP100), as it was previously assumed that all greenhouse gases (GHGs) remained stagnant within the atmosphere for centuries. This approach is still used today and can result in inaccurate analysis of the short-term and potent impacts of SLCPs.


Recently, two new approaches have emerged that may more accurately account for the short-term contributions of gases such as methane. One approach, named GWP20, examines methane over a 20-year period rather than a 100-year period. Methane traps 84 times more heat than CO2 over a 20-year period, subsequently dissipating from the atmosphere. Using a 100-year period, as is currently common practice, this number drops to approximately 28. Calculating impacts using a 20-year time horizon yields values that are more reflective of the short-term global warming potential of methane, as well as its relatively quick dissipation from the atmosphere.

While looking at short-term impacts may momentarily draw the attention of corporations and other climate actors away from long-term carbon mitigation and removal efforts, an accounting approach such as GWP20 would incentivize entities to prioritize methane within their climate action plans much more than they do today. For example, we can imagine a world in which a company would set a methane-specific target with a period equal to the lifespan of the gas – approximately 12 years. Likewise, reduction plans would separate out and potentially prioritize SLCPs over less potent and longer-lived stock gases such as CO2.

The other proposed approach to more accurately reflect the global warming impact of SLCPs is known as GWP*. This approach uses GWP100 as a baseline and reflects changes of methane entering and breaking down within the atmosphere. Here, the approach treats methane as a pulse emission, or temporary pulse, instead of as a constant agent of warming, or cumulative input. GWP100 assumes that methane emissions will cause warming for approximately 12 years and then rapidly subside. This is counter to stock gases such as CO2, which accumulate over time and persist in the atmosphere for 300-1,000 years. In short, under GWP*, the composition of companies’ GHGs are treated not on an “apples-to-apples” basis but on an “apples-to-oranges” basis.

While GWP* has been recognized by leading industry sources as a technically sound method, the approach has garnered support as well as criticism from industry professionals. A key concern of critics is that this type of significant shift in methodology would redefine the current net zero paradigm and conflict with established approaches to disclosure, target setting, and operationalizing of reduction goals. For example, companies following GWP* should aggregate emissions from SLCPs separately from emissions from stock gases such as CO2. Additionally, reduction targets and mitigation strategies addressing SLCPs would need to be right sized to the gas’s global warming contribution and lifespan in the atmosphere.


Emissions accounting continues to be an evolving space, and we expect that the conversation around how to most accurately account for SLCPs such as methane will continue to gain momentum in the coming years, particularly among companies who emit (and/or mitigate) significant amounts of these short-lived GHGs.

While new approaches such as GWP20 and GWP* may take time to be refined and adopted and shouldn’t spark an immediate overhaul of corporate climate programs, we could anticipate if integrated into GHG inventories and emissions management, these approaches provide a path for more funding to flow toward research and removal of methane and SLCPs – funding that is critical in our current climate crisis. In 2020, methane represented approximately 11% of US emissions yet attracted only 2% of funding dedicated to emissions reduction efforts. Curbing the impact of methane and other SLCPs is a key contribution to mitigating global warming and the worst impacts of climate change.


Rebecca Billingsley is a second-year Masters of the Environment student at University of Colorado Boulder specializing in Renewable and Sustainable Energy with a focus in GHG accounting and carbon management.

Andrea Green is a Masters of the Environment student at University of Colorado Boulder studying Urban Resilience with a focus on corporate sustainability.

Kenny Prior is a Masters of the Environment student at University of Colorado Boulder working in the community economic development space within Colorado’s outdoor recreation economy.