Gwp*: Methane, Metrics And Confounding Science And Policy

Generated Summary

This blog post from TABLE (Transforming Animal Agriculture and Building Livestock’s Environmental Sustainability) discusses the complexities of greenhouse gas metrics, specifically focusing on GWP* (Global Warming Potential Star) and its application to methane emissions, science, and policy. It explores the challenges in quantifying the climate impacts of different greenhouse gases, particularly those with varying atmospheric lifetimes, and the implications of using GWP* for methane mitigation strategies. The post critiques the conventional GWP metric and introduces GWP* as a metric that claims to better reflect the climate impact of short-lived greenhouse gases like methane. It further examines the implications of GWP* on policy, particularly regarding the incentivization of methane emission reductions. The methodology involves reviewing the scientific basis of GWP* and assessing its potential influence on climate policy and mitigation strategies, including an analysis of various emission scenarios and their impact on radiative forcing and temperature change.

Key Findings & Statistics

• The Global Warming Potential (GWP) metric is used to measure the impact of a pulse emission on radiative forcing over a given time period. For example, the cumulative effect on radiative forcing over the next 100 years of emitting 28 tons of carbon dioxide (CO2) is the same as emitting 1 ton of methane (CH4).
• The GWP100 value for methane is 28.
• Emitting 0.01 MtCH4/yr over 100 years (total of 1 MtCH4) is much more similar in terms of both radiative forcing and temperature change to a pulse emission of 28 MtCO2, than emitting that one MtCH4 today.
• The US GDP is expected to fall at an annualized rate of 25 percent or more in the second quarter of 2020.
• The federal government’s economic rescue package, known as the CARES Act (H.R. 748), is for $2 trillion.
• Enacting the bills would amount to as much as $520 billion in federal spending and could support as many as 9 million American jobs.
• The metric value for methane should be calculated as: GWP*Methane = (4 – 3.75 Et-20 / EtO) * GWP100, where EtO and Et-20c are methane emissions today and 20 years ago, respectively.
• Sustained methane emissions increases of more than 1%/yr (or reductions of nearly 2.5%/yr) to make the proposed GWP* metric equal that of GWP100.

Other Important Findings

• The choice of greenhouse gas metric significantly impacts the assessment of the carbon footprint of products, such as beef and dairy, that emit large quantities of methane.
• The introduction of GWP* aims to better reflect the climate impact of short-lived greenhouse gases like methane.
• GWP* compares pulse emissions of long-lived gases (e.g., CO2) with a continuous emission of short-lived gases (e.g., CH4), so that the cumulative emissions of both gases are equivalent if compared using the standard GWP metric.
• The GWP* metric is presented as a superior measure compared to GWP in measuring emission pathways and targets.
• A constant level of methane emissions results in constant atmospheric concentration levels.
• Stable methane emissions “make no further contribution to warming” and should not be penalized.
• There is a need for incentives to also reduce the emissions that maintain the current warming.
• The argument for incentives is based on the concept of “grandfathering” in environmental policy, which gives preferential treatment to pre-existing resource users.
• The benefit of GWP* is that it clearly quantifies the climate change resulting from emission scenarios for greenhouse gases with different atmospheric lifetimes.
• Standard GWPs, on the other hand, are better suited for making comparisons between commodities or production systems.

Limitations Noted in the Document

• The blog post does not detail the academic arguments of the original GWP* paper.
• The post suggests that a constant level of emissions may lead to no additional warming beyond current levels, but it does lead to more warming than if the CH4 was not emitted.
• The argument that the incentive should be a subsidy for reduced emissions, rather than a tax on actual emissions, is an example of grandfathering.
• The post acknowledges that using the GWP* metric as an argument for the position that methane emissions should be grandfathered is confounding science and policy.
• The blog post primarily focuses on the scientific basis of GWP* and its policy implications and does not provide a detailed economic or social analysis.

Conclusion

The central argument is that the choice of greenhouse gas metric significantly impacts the assessment of the carbon footprint of products, particularly those in animal agriculture. The introduction of GWP* seeks to offer a more accurate reflection of the climate impact of short-lived gases like methane. The blog post underscores the potential benefits of GWP* in quantifying climate change from different emission scenarios and guiding policy development. However, the author cautions against the uncritical application of GWP*, especially concerning grandfathering methane emissions. A key takeaway is that the choice of the right metric is essential for effective policies. The post concludes with the need for a more nuanced understanding of climate change and climate policy, which recognizes that different metrics can complement each other and contribute to a more comprehensive approach to addressing climate change. The future of climate policy relies on the ability to use knowledge in a way that promotes outcomes that are environmentally beneficial and equitable. The societal challenge now is for policy makers to use that knowledge when developing climate policies that lead to outcomes that are both environmentally beneficial and equitable. The discussion about which metric to use ultimately needs to be informed by broader considerations than just climate science.