Established climate metrics such as Global Warming Potentials (GWPs) are frequently used to relate greenhouse gas (GHG) emissions to globally averaged temperature change or to define emissions reduction targets. However, this single-basket approach of combining GHGs that have different lifetimes (e.g., methane and CO2) into CO2-equivalents results in ambiguous warming impacts because it obscures the distinct time-dependent effects of each GHG. Here we develop an alternative approach that separates short- and long-lived pollutants, aka a multi-basket approach, and investigate its ability to meet climate goals. We show that this multi-basket always outperforms single-basket approaches (e.g., GWP100, GWP20, GWP*), reducing overshoot of a near-term temperature goal by a factor of seven. Out of this work, we also developed an alternative to GWP for methane that more accurately indicates its temperature change. This metric, termed Sum44, is the 44-year cumulative sum of methane emissions, and is comparable to GWP* in projecting temperature change, but with fewer of its implementation challenges. We finally propose how to use Sum44 when considering policy controls to meet near-term climate change targets.
Dr. Julie Miller is a Research Associate at the Institute for Governance & Sustainable Development (IGSD). She supports their work on short-lived climate pollutants, particularly methane, and has focused on policy-relevant metric science. Prior to IGSD, Julie was a postdoctoral researcher at UCLA focused on ant colony behavior. She obtained a PhD in Behavioral Ecology from Cornell University and has a BA in Biochemistry.
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