What does lowering the United States’ greenhouse gas emissions accomplish for climate change, if most emissions come from other countries?

The U.S. is the second largest emitter on the planet. Reducing U.S. emissions will make a measurable impact on global warming on its own, and can encourage other countries to cut their own emissions too. 

May 30, 2024

Today, U.S. climate-warming greenhouse gas emissions account for roughly 14 percent of the worldwide total.¹ That fraction could shrink in the coming decades, because the United States has made significant investments in clean energy and electric vehicles, while reducing its use of climate-polluting fossil fuels. Already, emissions have been falling in the U.S. over roughly the last two decades.¹

Some other regions have shown similar trends. Fossil fuel use in the European Union has been dropping since 1990,² and emissions peaked in 1979.¹

Meanwhile, fossil fuel use in some other countries is climbing. China is now the world’s largest emitter of greenhouse gases,¹ and in 2022 approved more coal plants than the rest of the world combined.³ India is the third largest emitter, and while it’s well behind China and the U.S, its emissions are rising quickly.¹
 
So the United States plainly can’t “solve” climate change on its own. Nonetheless, as the world’s second largest emitter, U.S. actions to reduce greenhouse gases are essential—both in raw numbers, and because the U.S. can be uniquely influential in encouraging more climate action around the world. 
 
The U.S. has cumulatively emitted the most greenhouse gases by a large margin. To many countries, U.S. commitments to emissions reductions are a matter of fairness. The U.S. and other developed nations became rich by burning fossil fuels, and cumulative U.S. emissions are the biggest driver of climate change to date. And while all nations are suffering from climate change now, less-wealthy countries will bear the brunt of the impacts. In global climate negotiations, leaders of developing countries have pointed out these inequities: wealthy countries have enjoyed the benefits of fossil fuels, and now less-developed countries are being pushed to do without them. Further, people in the U.S. still emit much more than most others on a per person basis. In 2022, U.S. residents emitted nearly 15 metric tons of carbon dioxide per person, while Chinese residents emitted less than 9 metric tons each. Per capita emissions in India, Peru, the Philippines, and Namibia were less than 2 tons, and many African nations emit less than one-half ton per person per year.¹
 
The U.S.’s historical emissions and its wealth mean it plays an important role as a leader in global climate negotiations, says John Sterman, director of the MIT Sloan Sustainability Initiative, who studies global climate policymaking. Serious commitments from the United States—which still relies heavily on fossil fuels—can encourage other countries to make their own commitments. “The United States is the largest economy and the largest cumulative emitter in the world—every nation looks to us for leadership on this issue,” Sterman says. “If we delay action, other countries are likely to do the same.”
 
In fact, we have a recent example of the United States stepping back from climate commitments. After he was elected in 2016, former President Donald Trump withdrew the United States from the UN-brokered Paris Accord, a global climate agreement virtually every country in the world had agreed to. After the U.S. left, Sterman says, the pace of climate action slowed. As President Trump rolled back climate actions that were reducing emissions from vehicles and electric power plants, methane from oil and gas production, and fluorinated gases used in refrigeration, some other countries felt less pressure to make climate commitments or even rolled back their own regulations.  

Since 2021, the U.S. once again became a leader in confronting climate change. The U.S. rejoined the Paris climate agreement and its return to global climate negotiations has helped lead to new progress, including a global declaration in 2023 that, for the first time, called for a “transition away from fossil fuels.” The U.S. passed legislation including the Infrastructure Investment and Jobs Act and Inflation Reduction Act, which are encouraging production of clean power, boosting energy efficiency, and building infrastructure needed for further growth of clean energy.
 
That legislation builds on past policies like the American Recovery and Reinvestment Act of 2009, which invested in research, development and manufacturing of technologies like solar panels and electric vehicles. Those technologies are now manufactured and used worldwide—another way U.S. climate action has global impacts. “Wind and solar power are now cheaper than fossil fuels in most places around the world,” says Sterman. “Energy storage and technology to move power from where it is abundant to where it is needed are improving rapidly. Innovation and adoption of these technologies keep lowering the costs, and lower costs stimulate more adoption in a virtuous cycle.”

But while U.S. leadership is critical, no one nation can solve the climate crisis alone. If every country behaved as though its emissions didn’t matter, no one would take action and the world’s temperature would continue to soar. “We all have a common duty to reduce greenhouse emissions,” Sterman says. “To avoid potentially catastrophic harm from climate change, every nation must build a clean economy that cuts their emissions deeply and rapidly, achieving net zero by around mid-century.  Doing so will create a healthier, safer, more equitable and more prosperous future for all.”

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