US Climate Action in a Paris Committed World: What's at Stake?

Abstract:

Efforts to keep global mean temperature increases to below 1.5-2°C above pre-industrial levels will require sustained action by a coalition of nations and sub-national actors such as states, cities, regions, and businesses. The ambitiousness of new global Nationally Determined Contributions (NDCs) will hinge in part on post-2020 climate action in the United States, where there is high political uncertainty ranging from a rollback of current emission-abating measures to federal re-engagement with a net zero greenhouse gas (GHG) commitment for 2050. We use an integrated assessment model (Global Change Analysis Model – GCAM) to examine US policy scenarios to 2030 and NDC scenarios in the rest of the world to explore the importance of US action in achieving short-term and long-term climate targets. We will present the impacts of national and sub-national climate policy and international prices for fossil and bio-energy commodities on state-level GHG emissions in 2030, forecast how the extrapolation of current state-level ambition level affects state and nation-wide emissions in the long term, and provide a range of global temperature outcomes related to short-term political uncertainty in the US, and its potential impact on ambition in the rest of the world. Our work will provide a playbook to US policymakers seeking to enhance US climate action, and will serve as a guide to the international community on the importance of US participation in the Paris Agreement for avoiding dangerous levels of climate change.