Following the release of a major climate report last year, U.N. Secretary-General António Guterres warned that the “climate time-bomb” was ticking. Standing behind a podium emblazoned with the United Nations symbol of a globe encircled by olive branches, Guterres declared, “Our world needs climate action on all fronts — everything, everywhere, all at once.”

That call to action (possibly inspired by the movie of the same name) turns out to be a decent summary of what it takes to tackle rising carbon emissions. According to a new study out Thursday in the journal Science, countries have managed to slash emissions by putting a price on carbon, but the biggest cuts came by adopting a combination of policies. Seventy percent of the instances where countries saw big results were tied to multiple actions that generated “synergy.”

“There really isn’t a silver bullet,” said Felix Pretis, a co-author of the study and an economics professor at the University of Victoria in British Columbia, Canada. “That goes a bit against the conventional wisdom that economists have been saying that carbon pricing is the one thing we should push for.”

Pretis and researchers in Germany, France, and the United Kingdom looked for big drops in countries’ emissions and compared those results against the policies that had been adopted. Using machine learning, they analyzed 1,500 policies across 41 countries between 1998 and 2022, and found just 63 instances in which countries substantially slashed emissions. In total, these cuts added up to between 600 million and 1.8 billion metric tons of carbon dioxide. 

“I feel like there’s so much gloom and doom around climate policies, that nothing really happens, but actually, we’ve made a fair amount of progress,” Pretis said.

Part of the reason that the study only found 63 success stories is because it set a high bar in terms of emissions reductions, Pretis said. “But at the same time, we also see lots of policies having been implemented that don’t really bite.” Governments are falling short of their climate targets set in the 2015 Paris Agreement by about 23 billion metric tons of CO2. The problem isn’t just caused by a lack of ambition, the study says, but a lack of knowledge in terms of what policies work in practice.

Carbon pricing, whether through a carbon tax or a cap-and-trade program, was “a notable exception” in that it sometimes led to large emissions cuts on its own, the study says, and worked particularly well for emissions from industry and electricity. However, “it works even better if you complement and package it up as a policy mix,” Pretis said.

For example, the United Kingdom saw a 19 percent drop in emissions from the electricity sector between 2012 and 2018 after the European Union introduced a carbon price for power producers. Around the same time, the U.K. had implemented a host of other steps, including stricter air pollution standards, incentives for building solar and wind farms, and a plan to phase out coal plants. Similarly, China cut its industrial emissions by 20 percent from 2013 to 2019 through a pilot emissions-trading program, but also by reducing fossil fuel subsidies and strengthening financing for energy-efficiency investments.

To cut emissions from transportation and buildings, the study shows that it’s an even better idea to pair together multiple tools. Regulation is the most powerful policy for reducing emissions from transportation, and it can work well alongside carbon pricing or subsidies. The study also stresses that different policies might be effective in different contexts. The researchers found that carbon pricing was less effective in developing economies, places where regulations to limit pollution and investments in green technologies might be a better fit.

Gernot Wagner, a climate economist at Columbia Business School, said the study shows what measures to curb carbon emissions have been politically possible, but it shouldn’t necessarily serve as a guide for future policymaking. “It doesn’t capture policies that never passed — including those that would have been wildly successful but didn’t pass precisely because they would have been so effective.” 

Because of the bounds of the study, it also missed some of the most significant climate policies, Wagner said, pointing to the carbon taxes Sweden’s government passed in the early 1990s and the Inflation Reduction Act, signed by President Joe Biden in 2022. The United States’ landmark climate law invests hundreds of billions of dollars in clean energy and tax credits toward low-carbon technologies like heat pumps. The law is estimated to cut emissions by 40 percent by 2030, compared to 2005 levels.

“I wouldn’t be surprised if this exercise gets repeated five, 10 years from now, the Inflation Reduction Act would show up” as causing a big drop in emissions, Wagner said.