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A new paper released today in the open-access, peer-reviewed journal Nature Communications demonstrates how combining existing sub-national climate action with expanded national strategies in the United States will be critical to reach scientifically informed climate goals—and finds that such a comprehensive approach could reduce emissions up to 49% by 2030, relative to 2005 levels. The paper, entitled "Fusing subnational with national climate action is central to decarbonization: The case of the United States," also illuminates how the significant scale of action driven by subnational actors can form a critical part of national strategies—not only in the U.S. but also in other countries—as nations around the world increase their ambition to address climate change under the Paris Agreement.

In reaching these conclusions, the paper illustrates that the coalitions of subnational actors in the United States are globally significant, representing almost 70% of U.S. GDP, 65% of the U.S. population, and over half of U.S. emissions. These are equivalent to the world’s second largest economy—roughly the size of China’s. Moreover, in addition to showing the potential reductions from a comprehensive, “all-in” climate policy that combines subnational with national actions, it also finds that even just the current commitments from these actors alone could reduce emissions by 25% by 2030, and expanded actions by could reduce emissions could reduce up to 37% by 2030, relative to 2005 levels—even without the federal government. 

“This paper demonstrates an important lesson from the past few years of experience in the United States—which is that despite the lack of climate leadership from the U.S. national government, the tremendous groundswell of climate leadership from subnational actors has not only made a real and lasting impact on our emissions trajectory, but has also laid a stronger foundation for stepped-up, future action from the Federal government,” says the study’s lead author, Prof. Nate Hultman, Director of the Center for Global Sustainability at the University of Maryland. 

“Through this work, we have learned that the tremendous and growing level of subnational action witnessed across the U.S. in the past few years is something we would have had to do anyway. Such action can not only step up the level for future policies--potentially including new federal regulations and legislation--but it also helps root such action more firmly in local constituencies and political contexts. It’s only with that kind of grassroots support that we can successfully accelerate the transition to a clean economy that we know we need to see in the coming decade.”

“Federal government action on climate is critically needed and this report shows what can be accomplished if that action complements the ongoing subnational efforts rather than replacing them,” says co-author Kevin Kennedy, Senior Fellow for the U.S. Climate Initiative at World Resources Institute. “The analysis behind this report layers federal policies in the U.S. on top of the comprehensive scenario for enhanced action and offers a different approach for national climate action. This alternative strategy builds and expands on the innovative, ambitious climate action pioneered by U.S. states, cities, and businesses.”

Co-author Carla Frisch, principal at the Rocky Mountain Institute, adds, “We know that to continue this positive momentum, the U.S. needs a coordinated effort from all entities, including the federal government, to disseminate climate solutions at the speed and scale necessary to avoid the worsening impacts of climate change and build a clean, prosperous future for all.”

Assessing diverse subnational actions presents methodological challenges and this research advances a new approach to understanding the economy-wide emissions impacts, by first aggregating diverse data on subnational policies and commitments and then linking that aggregate information to a well-tested global modeling platform. “ Our approach, allows us to investigate the tremendous breadth of subnational policies at an unprecedented level of detail and still retain confidence in the overall projections,” notes Dr. Leon Clarke, a co-author of the paper and Research Professor at the Center for Global Sustainability, University of Maryland. 

There are strong parallels between subnational action in the U.S. and opportunities for other countries. Hultman notes, “While countries vary in their political systems and degree of policy devolution to subnational levels, these results underscore the importance of subnational engagement to support more ambitious and more effective implementation of national climate policies globally.” 

The open-access paper is available here


About the Center for Global Sustainability
The Center for Global Sustainability (CGS) at the University of Maryland School of Public Policy is helping drive the global engine of ambition critical to meet goals related to climate, development, and sustainability. We utilize a collaborative, interdisciplinary approach to deliver field-leading research, education, and engagement for policy impact. CGS is committed to fostering a just, equitable, diverse, and inclusive world both within our community and through our collaborative research and action across local, state, national and global scales. Launched in 2016, CGS has built a team of over 25 leading scholar-practitioners, researchers, and students and is based at the University of Maryland School of Public Policy. The University of Maryland is the major research university in the Washington DC area and a land-grant, sea-grant, public research university. It is ranked in the top 10 U.S. research universities with a $2.1 billion annual budget and combined $1.1 billion in combined annual research awards across campuses. 

About the Rocky Mountain Institute 
Rocky Mountain Institute (RMI)—an independent nonprofit founded in 1982—transforms global energy use to create a clean, prosperous, and secure low-carbon future. It engages businesses, communities, institutions, and entrepreneurs to accelerate the adoption of market-based solutions that cost-effectively shift from fossil fuels to efficiency and renewables. RMI has offices in Basalt and Boulder, Colorado; New York City; the San Francisco Bay Area; Washington, D.C.; and Beijing.

About the World Resources Institute
World Resources Institute (WRI) is a global research organization that spans more than 60 countries, with offices in Africa, Brazil, China, Europe, India, Indonesia, Mexico and the United States. Its more than 1,000 experts and staff work closely with leaders to turn big ideas into action at the nexus of environment, economic opportunity and human well-being. More information on WRI can be found at or on Twitter @WorldResources.