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Jessika E. Trancik, Atlantic Richfield CD Assoc Prof of Energy Studies
Francis O’Sullivan, Director of Research, MIT Energy Initiative
Sloan Collaborator: Prof. Susan Solomon, EAPS
Last December in Paris, most countries agreed to nationally-determined reductions in carbon dioxide (CO2) equivalent emissions, making this a notable year for global climate policy. This progress underscored the importance of choosing wisely among equivalency metrics used to compare the climate impacts of CO2 with other greenhouse gases. Our work over the past year focused on identifying promising metric designs and testing their performance by simulating their use in real world applications. We found that goal-inspired, threshold metrics, which incorporate information about climate stabilization targets into their design, exhibit performance improvements over the standard global warming potential (GWP) metric. At the global level, these goal-inspired metrics can mitigate the risk of methane (CH4)-induced overshoots in the near term. When applied to the U.S., these metrics suggest the need for deep CH4 cuts to accompany CO2-focused energy policy, which may require substantial innovation in the natural gas sector. Over the next year we plan to examine opportunities to mitigate emissions of CH4 and other short-lived greenhouse gases, including predictive methods to reduce leakage and policy approaches to incentivize the transition to lower-emission technologies.
Climate change is a multi‐gas problem, with significant contributions from CO2 and non‐CO2 greenhouse gas emissions. A large portion of these emissions result from energy technology use in electricity, transportation, and direct heating. This project will evaluate the climate impacts of energy technologies with high non‐CO2 lifecycle emissions, with a focus on CH4 and extensions to HFCs and other F‐gases. Current evaluation methods compare the heat‐trapping contributions of emissions over a fixed time horizon, but this approach does not account for the time‐dependent impacts shorter‐lived gases (including CH4 and HFCs) as climate stabilization targets are neared. This can result in assessment errors and unintended climate impacts. The first part of this project will develop emission‐time‐dependent metrics to compare the climate impacts of energy technologies and study their performance against climate policy goals. The second part will identify opportunities to mitigate these emissions, including improvements in existing technologies and transitions to new technologies. The results will inform timelines for mitigation, by considering CO2 and non‐CO2 reductions simultaneously.
Initial evaluations of mitigation opportunities will focus on CH4 leakage in the natural gas supply chain, a growing concern as current policies and low prices are encouraging a shift to natural gas‐supplied electricity. Not all devices in natural gas production and processing contribute equally to upstream emissions, and knowledge of the distributions across devices and sites can allow for cost‐effective mitigation. This research will also examine technology options for reducing HFCs, many of which are emitted through leakage and like CH4 have decadal atmospheric lifetimes. There are other commonalities as well. For both gases, two options for mitigation exist: (a) replace emitting technologies by alternatives with lower emissions or (b) reduce leakage rates. The results of this project will inform decisions on how to use both options strategically, informed by technology costs and assessments of climate impact. Technology‐focused mitigation policies are a promising approach for these non‐CO2 emissions, which originate from leakage and unlike CO2 are difficult to regulate directly.
This research will result in new understanding of the climate impacts of non‐ CO2 emissions from energy technology use and opportunities for mitigating these emissions. These results will be shared the EPA, which has recently proposed CO2‐ focused regulations for power plants and separate regulations for CH4. They will also be shared with the DOE, where they can inform evaluations of technology research and development funding proposals. The research results will be presented at conferences leading up to the UNFCCC Paris negotiations in December, 2015. Information on the value of mitigating non‐CO2 greenhouse gases is also relevant in the private sector, and this research will provide a basis for interactions with energy companies, car companies, and engine manufacturers who have expressed interest in the work.