Last week, the Trump administration announced it will begin the legal process of withdrawing from the Paris climate agreement. This symbolic move will have little impact. Whether the world reduces carbon emissions matters far more than whether the United States remains part of the agreement. The agreement was designed to tolerate noncooperation. While some observers worry that nations will tackle climate change only if everyone else does, too, the empirical record suggests otherwise. Right now, other nations are acting to reduce emissions. A Trump administration withdrawal will irritate other countries but won’t derail global action.

What does Paris require?

Under the Paris agreement, nations set their own goals, making pledges to reduce their greenhouse gas emissions as they see fit. This is a direct response to the failures of the Kyoto Protocol, which required developed nations to cut their emissions according to a rigorous set of targets and timetables. The United States did not join the Kyoto Protocol, and major emitters such as Canada and Australia either withdrew or did not sign on to its continuation.

The Paris agreement, by contrast, offers a flexible framework that requires all nations to take some action on climate change, however minimal, with the expectation that they will ratchet up their ambitions over time. Given that each country gets to make its own rules, President Trump’s lamentation that the agreement is “unfair” demonstrates a profound misunderstanding of its design. This decentralized approach, emphasizing national and subnational action, means that climate policy can be tailored to domestic economic concerns and political constraints. This increases the likelihood that governments will make national pledges they can actually keep — or so the logic goes.

The problem, therefore, is not who participates, or doesn’t, but rather how ambitious nations’ pledges to reduce emissions actually are. Right now, if all countries actually implement their national pledges under the agreement, the mean global temperature will rise by 3 degrees Celsius, or about 5.5 degrees Fahrenheit. This is far higher than the goal set in the Paris agreement to limit warming to 1.5 degrees Celsius.

The United States has already damaged the climate — and it’s set to get worse

The Paris agreement has served as a convenient target for the Trump administration, but the reality is the United States is the worst offender when it comes to global emissions. Historically, it is the largest emitter, responsible for about one-third of total emissions, and its per capita emissions are roughly twice as large as those of the next largest emitter. Many, including Trump, point to China’s emissions as a reason for inaction. But China overtook the United States as the world’s biggest emitter only in 2005, though some of these emissions are to produce exports for the United States and the European Union.

The damage is not just historical. Since 2016, the Trump administration has steadily eviscerated federal climate policy. It repealed President Barack Obama’s signature climate policy, the Clean Power Plan, and replaced it with new regulations that could increase emissions. It has also weakened fuel economy standards, which will also raise emissionsagainst the wishes of much of the auto industry. It’s trying to revoke California’s Clean Air Act waiver, which allows California to set air quality standards that are more demanding than federal rules. If the administration succeeds, that will probably increase emissions while reducing the use of electric vehicles. Previous research suggests such a move will not only affect California but have ripple effects through the U.S. economy. In short, the United States’ actual policy changes are more important than its moves to withdraw from the Paris agreement.

Cities and states are making climate policy, without the federal government

Governments around the world are preparing for yet another round of climate negotiations — in Chile in December. Meanwhile, within the United States, cities, states and businesses insist that “we are still in,” despite the looming federal withdrawal from the Paris agreement in 2018. A number of U.S. cities and states have set their own targets for reducing greenhouse gas emissions. Recently, New York state passed the Climate Leadership and Community Protection Act, which sets one of the world’s most ambitious climate goals, pledging that by 2050 it will reduce carbon emissions to 85 percent below 1990 levels.

Such efforts are making some progress toward emissions reductions; the U.N. Environment Program estimates that current efforts are reducing about 0.5 gigatons of CO2 (in 2018, the world emitted roughly 37 gigatons). One environmental group estimates that these commitments add up to about two-thirds of the U.S. pledge made as part of the Paris agreement. Still, the United States will not get there, much less achieve net-zero carbon emissions, unless the federal government gets involved.

A Green New Deal could move the needle

Discussions of a Green New Deal could play a critical role in changing federal policy. This congressional resolution, proposed by Rep. Alexandria Ocasio-Cortez (D-N.Y.) and Sen. Edward J. Markey (D-Mass.), aims to decarbonize the U.S. economy while reducing income inequality and expanding the social safety net. Though climate change has traditionally been a polarizing topic in the United States, at least some polls suggest public support for a Green New Deal is overcoming this divide.

The Paris agreement would survive a U.S. withdrawal. But the tougher political questions are: How quickly can carbon emissions be removed from the U.S. economy, and can climate and justice advocates, working with elected officials, build enough political support to do that?

Jessica F. Green (@greenprofgreen) is an associate professor in the department of political science and School of the Environment at the University of Toronto.