College Park, MD - October 22, 2018 - A bit over one year ago, in June 2017, President Trump announced his intent to withdraw the United States from the Paris Agreement on Climate Change. While formally the withdrawal cannot legally happen until just after the 2020 election, this announcement catalyzed a groundswell of new climate action across the United States. Within 72 hours of that announcement, a coalition of over 2,700 cities, states, businesses, universities, communities of faith, and others had committed to support the goals of the Paris Agreement through the “We Are Still In” coalition.  That coalition—now numbering over 3,500—is globally significant. It represents more than half of the U.S. population (173 million people) and nearly 60% of U.S. GDP ($11.4 trillion). If this coalition were a country, it would be the world’s third largest economy and the world’s fourth largest GHG emitter.

  Figure 1. (Left) The American coalition of real economy actors making commitments to climate goals is globally significant: Were it a country, it would be the world’s third largest economy and fourth largest GHG emitter (right).

Figure 1. (Left) The American coalition of real economy actors making commitments to climate goals is globally significant: Were it a country, it would be the world’s third largest economy and fourth largest GHG emitter (right).

Shortly thereafter, California Governor Jerry Brown and Former New York Mayor Michael Bloomberg (now UN Special Envoy for Climate Change) announced a partnership called America’s Pledge that would support this coalition in raising ambition even beyond what these many actors had already committed to do. This partnership was novel and innovative in linking closely three elements essential to scoping and raising ambition: engaging stakeholders and coalition members to better understand their goals and needs, analysis and research to evaluate new opportunities, and to assess the impact of potential and new commitments, and communications to facilitate new understanding across the coalition and with the broader public.

While the coalition is indeed significant, a key question is whether these actions can really make a difference. In other words, “What does it all add up to?” As such we sought to understand better the opportunities for action across the U.S. economy and developed a new modeling approach to answer that question. The America’s Pledge analysis team, co-led by the Center for Global Sustainability and the Rocky Mountain Institute, assembled a team of 51 co-authors across seven institutions[1] to aggregate the commitments, characterize new and feasible pathways to rapidly raise ambition, and estimate the overall impact of such actions on the overall U.S. emissions trajectory. The results are presented in our recent report Fulfilling America’s Pledge: How States, Cities, and Businesses are Leading the United States to a Low-Carbon Future

In this overview, I provide a short summary and commentary on the results of this effort, but readers are encouraged to consult the report itself, the executive summary, or the extensive technical appendix available online, for a fuller description as well as some interesting case studies of how these actions are happening already across the United States. Figure 2 below shows the interesting, top-line result from the report: feasible actions by states, cities, and businesses over the next couple of years could actually drive U.S. emissions close to (though not quite reaching) the U.S. Paris target for 2025 (otherwise known as our NDC or Nationally Determined Contribution).

  Figure 2. What does it all add up to? The purple line (bottom) shows that ambitious action by states, cities and businesses can drive emissions down to 24% below 2005 levels by 2025, within striking distance of the US NDC. The gold (top) line shows the impact of current commitments; the blue (middle) line shows the impact of ten specific climate action strategies described below.

Figure 2. What does it all add up to? The purple line (bottom) shows that ambitious action by states, cities and businesses can drive emissions down to 24% below 2005 levels by 2025, within striking distance of the US NDC. The gold (top) line shows the impact of current commitments; the blue (middle) line shows the impact of ten specific climate action strategies described below.

While the methodology was complex, the overall conceptual approach is straightforward. First, we built out pathways for three levels of ambition:

  1. The first level, which we call Current Measures, is simply the aggregation of existing commitments from states, cities, and businesses.

  2. The next level is based on a set of ten Climate Action Strategies which we built out based on both analysis and in consultation with many of the actors undertaking actions. These ten strategies represent opportunities that are potentially high impact (in terms of emissions reductions) and available for action now for actions by states, cities and businesses – in other words, they can be implemented today without the federal government. We then estimated how much these strategies could deliver based on vigorous implementation across a plausible set of states, cities, and businesses.

  3. The third and most ambitious level, Enhanced Engagement, expands the number of actions beyond ten, and allows for higher implementation across a slightly expanded, but still plausible, set of real economy actors.

After developing these three scenarios for ambition, we then estimated the implications of the commitments at the state level, making sure to eliminate double counting, using a new aggregation tool called ATHENA. We finally fed that into a global integrated assessment model with 50-state resolution in the United States (GCAM-USA) to obtain an estimate of those commitments on the overall U.S. emissions trajectory. This new methodology allows broad incorporation of the commitments made at multiple levels into an economy-wide assessment of emissions impacts.

The impact of the three levels of ambition is shown below in Figure 3. The first (far left) bar shows the level of U.S. emissions for all greenhouse gases in 2005 – about 6,500 million tonnes of CO2 equivalent. The second bar shows emissions for 2016, the most recent year we had data for, which shows a drop of about 12% from 2005 levels, about halfway to our Paris NDC of 26-28% below 2005 levels. These reductions have been driven by policies, consumer choices, and market forces. Now we start to look forward to 2025. The next (third) bar shows the emissions impact of an expected ~18% growth in GDP between now and 2025 would, all else equal, lead to a slight emissions increase of about 3%.

  Figure 3. Estimates of reductions from feasible real economy actions between now and 2025, grouped according to three levels of ambition in the study. Yellow shows impact of current commitments, delivering reductions of 17% below 2005 levels by 2025. Blue shows impact of 10 near-term, high-impact Climate Action Strategies, delivering reductions of 21%. Purple shows impact of expanded number of actions, more significant utilization of those actions, and broader participation – which would deliver reductions of 24%.

Figure 3. Estimates of reductions from feasible real economy actions between now and 2025, grouped according to three levels of ambition in the study. Yellow shows impact of current commitments, delivering reductions of 17% below 2005 levels by 2025. Blue shows impact of 10 near-term, high-impact Climate Action Strategies, delivering reductions of 21%. Purple shows impact of expanded number of actions, more significant utilization of those actions, and broader participation – which would deliver reductions of 24%.

And this is where it gets interesting. The yellow bar in Figure 3 shows the reductions that current commitments by states, cities, and businesses, as well as remaining federal policies would drive emissions to 17% below 2005 levels by 2025. This is nearly 2/3 of the way to the Paris target and represents significant progress against what otherwise would have been an increase of emissions over the next seven years.

The blue bar in Figure 3 shows the additional reductions that could be delivered by a concerted push on the 10 near-term, high impact Climate Action Strategies that are available to non-federal actors. The ten strategies, detailed here (and in the report), are: 1) Double down on renewable energy targets; 2) Accelerate the retirement of coal power; 3) Encourage residential and commercial building energy retrofits; 4) Electrify building energy use; 5) Accelerate electric vehicle adoption; 6) Phase down super-polluting HFCs; 7) Stop methane leaks at the wellhead; 8) Reduce methane leaks in cities; 9) Develop regional strategies for carbon sequestration on natural and working lands; and 10) Form state coalitions for carbon pricing. A focus on such strategies is feasible even under current political constraints, and could deliver significant impacts quickly: we estimate that vigorous implementation could drive emissions down 21% relative to 2005 levels by 2025.

Finally, the purple bar in Figure 3 shows enhanced engagement beyond just the 10 strategies, and with broader uptake. It was nevertheless constructed to be still feasible under real and current political constraints. This scenario would bring the United States very close to its Paris NDC, at 24% below 2005 levels by 2025. Our Paris NDC, which I helped develop when I worked in White House for Obama Administration, was a highly ambitious target even with full Federal action. The ability of states, cities, and businesses to come close to this target is therefore significant. One other way to look at this is that the enhanced engagement approach allows the U.S. to reach the NDC level by roughly 2026.

Importantly, we did not model the impact of potential new federal actions after 2020. While federal re-engagement (from both Congress and the Executive Branch) will be necessary for the United States to get on the required emissions pathway, we focused this study on opportunities for states, cities, businesses, and other actors both to contribute to reductions and build the right groundwork faster action after federal re-engagement.

Another way to look at the potential reductions is to divide the estimates out by sector, which are depicted Figure 4. Our assessment underscores the significant near-term importance of the power sector, using both reductions in coal power usage and increases in renewable energy deployment. But it also shows the collective significance of an approach that also targets near-term opportunities in the other major sectors of the economy.

  Figure 4. Estimates of reductions from feasible real economy actions between now and 2025, grouped by sector. The power sector provides significant near-term opportunities, but other sectors collectively add a lot and also deliver increasing reductions after 2025.

Figure 4. Estimates of reductions from feasible real economy actions between now and 2025, grouped by sector. The power sector provides significant near-term opportunities, but other sectors collectively add a lot and also deliver increasing reductions after 2025.

So that’s what it all adds up to. A concerted near-term effort, rooted in real economy actions and using policy levers available to cities, states, and businesses in the U.S. could drive down the U.S. emissions trajectory close to – although not quite reaching – our Paris target. Figure 5 shows a more detailed set of trajectories for each of the three levels of ambition including uncertainties. A key feature to note in this figure is the accelerating rate of reductions that these actions can deliver: compared to the recent rate of reductions of 1.1% per year, we estimate roughly 1.6% per year between 2016-2025; and after 2025, our estimate is that the rate accelerates further to roughly 2.1% per year. This rate is close to the 2.3% needed to bring the U.S. to deep decarbonization by midcentury. In other words, these actions now are not only helping to deliver real reductions, but are laying groundwork for faster action later.

  Figure 5. Estimates of potential reductions from feasible real economy actions between now and 2030. These actions deliver accelerating action after 2025: the recent rate of reduction was 1.1% per year; action between now and 2025 increases that rate to 1.6% per year, and that increases to 2.1% per year to 2030.

Figure 5. Estimates of potential reductions from feasible real economy actions between now and 2030. These actions deliver accelerating action after 2025: the recent rate of reduction was 1.1% per year; action between now and 2025 increases that rate to 1.6% per year, and that increases to 2.1% per year to 2030.

The federal political system and free market economy in the United States devolves significant policymaking authority to real economy actors in other levels of government and to companies and other organizations. Our Fulfilling America’s Pledge report showed that the globally significant group of actors committing to climate action in the U.S. are already on track, with current commitments, to drive U.S. emissions to 17 percent below 2005 levels by 2025, roughly 2/3 of the way to the NDC. Broader engagement within realistic constraints could reduce emissions by more than 24 percent below 2005 levels by 2025--within striking distance of the Paris target, and setting up the U.S. economy for accelerating decarbonization after 2025.  This analysis demonstrates that climate action can be led by the bottom-up efforts of real economy actors—but only with strong domestic and international collaboration and engagement. The high ambition levels and the potential federal re-engagement both require new modes of collaboration as well as strong political backing. So elections matter and creative approaches to organizing will be key.

The recent IPCC 1.5 report underscored the urgency for quickly developing not only new technologies, but new modes of social and political organization to rapidly mobilize climate action on a global scale. And in the spirit of the Paris Agreement, which calls on all Parties to help reach global climate goals, new modes to better meld sub-national climate actions with national ambition will be an essential part of ratcheting up global ambition in advance of 2020. America’s Pledge provides one model of integrating these new real economy coalitions with analytical approaches to engage and incorporate this ambition into national processes. Pursuing significant engagement domestically in concert with rapidly developing international approaches to fusing sub-national with national ambition will be an essential element to bringing the U.S. and global communities on track toward the rapid decarbonization that we know will be needed. And in doing so, we will be able to collectively move toward a cleaner, healthier and more prosperous future.


Author: Nate Hultman

Nate Hultman is Director of the Center for Global Sustainability and lead author on the Fulfilling America’s Pledge report. 51 co-authors across 7 institutions contributed to the report, and it would not have been possible without the input and support from many additional people across the community. The report was made possible with support from Bloomberg Philanthropies.


1. Nate Hultman and Koben Calhoun served as the report’s lead authors, with guidance and coordination from Paul Bodnar. Writing, modeling, and analysis team members from contributing organizations include: University of Maryland: Nate Hultman, Shannon Kennedy, Christina Bowman, Arijit Sen, Woijciech Krawczyk, Jiehong Lou, Jessica Frech, Florencia Sanchez, and Andrea Prada. Rocky Mountain Institute: Paul Bodnar, Koben Calhoun, Annie Benn, Ellen Franconi, E.J. Klock-McCook, and Michael Liebman. World Resources Institute: Kevin Kennedy, Kristin Igusky, Michelle Manion, Tom Cyrs, James DeWeese, Karen Chen, James Mulligan, Tyler Clevenger, Joe Thwaites, Yelena Akopian, Stephen Russell. Peter Hansel (Independent Contractor). Environmental Defense Fund: Nathaniel Keohane, Daniel Francis, Pam Kiely, Charlie Jiang, Mark Brownstein, Matt Watson, Jonathan Peress, David Lyon, Hilary Hull. American Council for an Energy-Efficient Economy: David Ribeiro, Weston Berg, Stefen Samarripas, and Shruti Vaidyanathan.  CDP: Andrew Clapper, Luz Cervantes Valdivieso, Zoya Abdullah, and Ian van der Vlugt.  The Cadmus Group: Jon Crowe, Egan Waggoner, Graham Stevens, Miles Gordon, Emily Messer, Neil Veilleux and Jeremy Koo.