Mayor of Bonn Ashok-Alexander Sridharan, former California Governor Arnold Schwarzenegger, and COP 23 President Prime Minister Frank Bainimarama of Fiji attend the COP23 UN Climate Change Conference, in Bonn, Germany, November 2017.
Mayor of Bonn Ashok-Alexander Sridharan, former California Governor Arnold Schwarzenegger, and COP 23 President Prime Minister Frank Bainimarama of Fiji attend the COP23 UN Climate Change Conference, in Bonn, Germany, November 2017.
Wolfgang Rattay / REUTERS

President Donald Trump’s announcement of the United States’ withdrawal from the Paris agreement on climate change last summer triggered an important public debate. Although many lamented the move as a major climate setback, others disagreed and called for calm, on the theory that if U.S. cities, states, and businesses continued to reduce their emissions the United States could still meet its carbon reduction commitments, even without backing from Washington. Sure enough, thousands of municipalities, companies, universities, and civil society groups reaffirmed their support for the Paris agreement in the wake of Trump’s announcement, and many set their own climate goals.

The Global Climate Action Summit in San Francisco earlier this month put this debate over the significance of local and private-sector climate initiatives back in the spotlight. The summit was a platform for dozens of new announcements and pledges from municipal, state, and business leaders, including plans for zero-waste cities and zero-emissions buildings. Yet skeptics will ask: Are these pledges significant? Will they lead to significant emissions reductions that counteract some of the inaction by national governments, including the Trump administration’s series of environmental rollbacks?

We, along with co-authors from NewClimate Institute and PBL Netherlands Environmental Assessment Agency, set out to answer these questions in a new report launched prior to the summit. We examined close to 6,000 individual city and region pledges and more than 2,000 business commitments from ten of the world’s highest-emitting regions, as well as 21 collective pledges (often referred to as international cooperation initiatives) made by a mix of private sector, civil society, city, regional, and national government participants. We found that these pledges, if realized, would deliver significant carbon mitigation on a global scale.

Combined, the individual commitments would mitigate an additional 1.5 to 2.2 gigatons of carbon dioxide equivalent—an amount roughly double Canada’s annual emissions—above what national policies alone would achieve by 2030. When cities, regions, and companies act together alongside national governments in international cooperation initiatives, the potential impact is much greater, ranging from 15 to 23 gigatons of carbon dioxide equivalent mitigation—enough to reduce annual global emissions by approximately one-third by 2030, putting the world on track to achieve the Paris agreement’s goals of limiting global temperature rise to 1.5 to 2 degrees Celsius above preindustrial levels.

Profound reductions are particularly promising in efforts to tackle greenhouse gases other than carbon dioxide, from sectors like waste and agriculture. The Climate & Clean Air Coalition, an international cooperative initiative, is working to reduce emissions of potent greenhouse gases such as methane, which has a global warming potential 20 times higher than that of carbon dioxide. Improved land use could bring about even greater carbon reductions. For example, the Bonn Challenge—a 56-member international cooperative initiative—has set a goal of restoring 350 million hectares of degraded and deforested land by 2030.

In the United States—which has emitted more carbon than any other nation in history—state, local, and business leaders have stepped up as the national government has backpedaled. More than 3,000 mayors, governors, CEOs, and university presidents have signed on to the We Are Still In movement, pledging to honor the country’s climate change commitments articulated in the Paris agreement. Across the United States, more than 100 companies have set meaningful targets to reduce their emissions and more than 90 U.S. cities and counties have adopted goals of using 100 percent renewable energy. In total, we found that U.S. city, state, and business pledges could provide at least half of the emissions reductions needed to meet Washington’s former Paris agreement commitment. If enacted, these pledges could lower U.S. emissions by 670 to 810 megatons of carbon dioxide equivalent per year by 2030, an impact on par with retiring over 160 coal-fired power plants. The reductions are coming from over 900 companies, 19 states that account for just under half of the country’s population, and nearly 100 cities that represent 13 percent of the country’s population. Together, these actors contributed 38 percent of the country’s total carbon footprint in 2015. They have all made commitments that specifically pledge to cut emissions or shift to renewable energy.

There are, however, other countries included in our analysis whose city and business commitments do not add up to the same kind of additional impact as those from the United States. Individual city and company contributions from China, for example, showed far less than we expected, given the country’s status as the world’s number one greenhouse gas emitter. We evaluated pledges by 22 Chinese city and regional actors and 140 Chinese companies, which will contribute up to 155 million tons of carbon dioxide equivalent mitigation above what current national policies alone would achieve by 2030—a mere fraction of the total for U.S. cities, regions, and companies. One reason for the low local reductions numbers is China’s vertically integrated environmental governance system. Most of the country’s climate and energy policies are set by the national government and implemented at local levels through binding targets, making these top-down policies much stronger drivers of climate action than participation in international climate change initiatives and reporting platforms. Examining the national-level emissions data for China, it is clear that the country is on track to meet its Paris targets years ahead of schedule, largely due to its explicit policy demands on cities to deliver emissions cuts.

For all the impressive state and local initiatives in the United States, then, China’s example shows that national policy matters. Moreover, the Trump administration’s efforts to weaken or eliminate federal domestic climate policies could threaten some of the gains made by subnational jurisdictions and non-state actors. The Obama administration’s Clean Power Plan—which would have prompted states to enact policies to cut power plants’ greenhouse gas emissions—is now stuck in legal uncertainty. Trump also aims to reverse the Corporate Average Fuel Economy (CAFE) standards, which gradually ratchet up vehicle fuel-economy requirements nationwide. The current administration’s strategy would remove the ability of California—and 12 other states—to retain their current Zero Emission Vehicle deployment and stricter emissions standards, which set more ambitious goals than national policies. It could also stifle innovation in the auto industry, putting a damper on the ability of both states and the private sector to create climate change solutions.

This added uncertainty comes at a critical time for the global response to climate change. Individual countries’ current pledges under the Paris agreement provide just one-third of the emissions reductions needed to meet the agreement’s overall goals and prevent disastrous levels of temperature rise. By 2020, national governments will be asked to update their Paris pledges, and will hopefully take into consideration what their cities, regions, and companies can contribute. Washington may have walked away from these commitments, but if the initial response to Trump’s withdrawal is any indicator, subnational groups are unlikely to back down.

You are reading a free article.

Subscribe to Foreign Affairs to get unlimited access.

  • Paywall-free reading of new articles and a century of archives
  • Unlock access to iOS/Android apps to save editions for offline reading
  • Six issues a year in print, online, and audio editions
Subscribe Now
  • ANGEL HSU is an Assistant Professor at Yale-NUS College, an Adjunct Professor of the Yale School of Forestry and Environmental Studies, and Director of Data-Driven Yale. AMY WEINFURTER is a Research Associate at Data-Driven Yale.
  • More By Angel Hsu
  • More By Amy Weinfurter