What Are the Best Policies for Reducing Carbon Emissions? A New Study Has Some Answers

A systematic analysis of more than 1,500 climate policies from around the world found that only 63 were successful, reducing average emissions by 19 percent on average.

The research, published August 22 in the journal Science, finds that policies are more effective when implemented with a variety of other policies, instead of alone.

“We systematically evaluated policy measures that have rarely been studied until now, providing new insights into well-designed combinations of complementary policy instruments,” Nicolas Koch, a co-author of the study and an environmental economist at the Mercator Research Institute on Global Commons and Climate Change in Germany, says in a statement from the Institute for New Economic Thinking at the University of Oxford.

The study also shows the types of policies that would be most helpful in meeting goals for emissions reductions across different sectors.

“This study gives me confidence that we know what to do and how to do it,” Julio Friedmann, a carbon removal expert at the carbon management firm Carbon Direct who did not contribute to the findings, tells the Wall Street Journal’s Eric Niiler.

Still, the research also highlights that many policies have not been successful in meeting emissions reduction goals.

“This study provides a warning to countries around the world that their climate policies have had very limited effects so far,” Xu Chi, an ecologist at Nanjing University who was not involved in the research, says to Nature News’ Xiaoying You. “Existing policies will need to be re-evaluated, and changes will need to be made.”

Currently, countries around the world are not doing enough to limit global warming to between 1.5 and 2 degrees Celsius above pre-industrial times—the aim of the Paris Agreement. A 2023 analysis from the United Nations found that the world is on pace for 2.5 to 2.9 degrees Celsius of warming based on pledges under the Paris Agreement, and predicted emissions must fall by 28 to 42 percent by 2030 to meet goals for limiting warming.

Researchers say in the new paper there is a question about which policies are most successful at reducing emissions. The new study looks at policies implemented between 1998 and 2022 across 41 countries from six continents that accounted for 81 percent of global emissions in 2019.

“To my knowledge, it is a first-of-its-kind study providing such a global evaluation,” Jan Minx, an environmental economist with the Mercator Research Institute on Global Commons and Climate Change in Germany who did not contribute to the findings, tells Nature News.

To determine which policies were most effective, the researchers combined machine learning methods with statistical analysis, identifying 63 policies that reduced total emissions by between 0.6 and 1.8 billion metric tonnes of carbon dioxide.

The analysis supported the theory that mixing different types of policies is effective. In the U.K., banning coal-fired power plants worked when it was combined with tax or price incentives. The same was true for banning combustion engine cars in Norway. Such implementations didn’t significantly reduce emissions alone and needed to be combined with additional policies.

“The commonality in those successful cases is where we see subsidies and regulations being combined with price-based policy instruments,” Koch tells the Wall Street Journal. “This means carbon pricing, and it could be energy taxes, it could be vehicle taxes.”

The study also found that successful strategies differed between countries—in developed countries, carbon pricing was effective, while regulation was successful in developing countries, according to a statement from the University of Oxford.

The authors conclude that if all the countries in the study created emissions reductions typical of the successful policies identified in the study, they could move 26 to 41 percent closer to meeting the Paris Agreement’s targets.

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.