Promising climate action is one thing, but it’s not always easy for countries to deliver on the pledges they’ve made to reduce greenhouse gas emissions under the Paris Agreement. New research published Thursday in Nature Climate Change now shows that countries with the most ambitious climate plans also are the most likely to follow through.

One important question the study helps answer is whether the mechanisms of the Paris Agreement are working, said co-author Astrid Dannenberg, an environmental and behavioral economist at the University of Kassel in Germany. The 2015 climate pact is unique because it’s completely voluntary, leaving it up to governments and countries to “offer what they think is appropriate and feasible,” she said.

“And once everyone has offered something, then you can compare,” she said. “You can say, OK, this isn’t enough, we need to do more, and then the whole procedure starts again. And I think the results show that it is working, at least some of the pledges are credible. So there is something that countries can build on.” 

Whether or not they will do that is still up in the air, she added.

“Will they use the opportunity? Will they make more ambitious pledges, because it’s also very clear that the pledges right now are not enough to achieve the 2 degree target or the 1.5 degree target,” she said. “Our data is also showing that the international climate goals are still out of reach right now. But we also see that the Paris Agreement can initiate the dynamics that are needed to become more ambitious in the future.”

The study also shows that countries with “high quality” political institutions are seen as those that are most able to deliver credible climate pledges, said co-author Marcel Lumkowsky, who is studying the effectiveness of the Paris Agreement at the University of Kassel. 

“I think that this is a very important outcome, also to see what can be done in countries that may be struggling to reach their targets,” he said. “Maybe they need help improving their institutions and with capacity building, and things like that.” 

Lead author David Victor, a professor of innovation and public policy at the School of Global Policy and Strategy at the University of California, San Diego, said the study shows that the Paris Agreement has spurred countries to make ambitious pledges.

“Our results indicate that the framework of the agreement is working pretty well,” he said. “The Paris Agreement is getting countries to make ambitious pledges; last year nearly all countries updated those pledges and made them even more ambitious. What’s needed next is better systems for checking to see whether countries are actually delivering what they promise.”

US Efforts Rated as Least Credible

Many efforts to measure the effectiveness of the Paris Agreement to date are based on taking pledges at face value and plugging them into a climate model, which doesn’t account for whether or not countries are actually doing what they say they will.

Victor’s team took a different approach, surveying more than 800 climate policy experts, climate diplomats and scientists from all over the world including people who are part of key policy decisions, enabling them to evaluate what their countries and other countries are likely to achieve. They were asked to rate member nations—their own country included—by comparing pledge ambition and credibility with what countries feasibly can do, given their economic and political conditions. 

A subset of survey responses from eight countries plus the European Union were selected for being most relevant to climate mitigation policy, and rated Europe’s goals as the most ambitious and credible. Europe is followed by China, Australia, South Africa and India. The U.S. and Brazil came in last place in the credibility category and second to last, after Saudi Arabia, in terms of ambition.

“What’s different about our approach is that we are looking at credibility through the eyes of the people who have the best intuition about how all the complex policy and political processes in each country actually work,” Victor said. “ And for phenomena like this, where the outcome of national policy depends on a lot of complex factors that are hard to measure systematically—expert judgment of this type is really useful.”

Lumkowsky said the poor U.S. showing is partly because the survey was completed in 2020, under the climate policies of the Trump administration and a U.S. pledge dating back to 2016. 

“So maybe if we would do the survey now, the ratings would be a bit higher, because there is a new pledge and the Biden administration is focusing more on these issues,” he said.

The survey was completed before the Inflation Reduction Act was signed by Biden, Dannenberg said, adding that nevertheless the U.S. still seems to have a credibility problem among the experts surveyed. 

“The U.S. is not seen as a very reliable leader,” she said. “This act had difficulties to come through and I think people were very relieved when they managed to get it through. You don’t know who will be the next president, and you don’t know what will happen next. I think the whole world is nervous about the U.S. and I think this is what we see in our data.”

Victor said the IRA will help accelerate U.S. decarbonization, but it doesn’t put the U.S. on a permanent path, and a big gap remains between what the U.S. pledges and what the rest of the world believes it might actually do.

“The U.S. ranking is fundamentally rooted in our flaky federal policy, to the extreme, the flip flopping from Obama to Trump to Biden,” he said. “But I think there is something deeper here that we can’t measure in our survey but which I see as an analyst. The country is divided politically and thus our key challenge is, how can the country put together and hold together a policy for the long haul? Serious deep decarbonization requires credible long-term signals to industry and the rest of the economy.”

Federica Genovese, a political scientist at the University of Essex, said the research can help decision-makers shape better climate policy.

“If I were to brief decision makers with this article, I would stress the importance of listening to both scientists and diplomats, because the former have technical knowledge, but the latter are better at assessing the political feasibility and ambition of pledges,” said Genovese, who was not involved in the new study. “I would also warn about the importance of keeping democratic institutional processes healthy, as these seem to matter a lot for the credibility of climate pledges.”

Ambition Equals Credibility

Dannenberg said the most surprising result of the research was that there was a positive correlation between the ambition and credibility of climate pledges. “We expected, more from a theoretical perspective, that, if a pledge is very ambitious, it would be less credible,” he said.

Countries with the boldest pledges are also the most likely to achieve their goals. Europe takes the lead with the strongest commitments that are also the most credible, according to the survey, while the U.S., despite having a less ambitious commitment under Paris, is not expected to meet its pledges. 

In Europe, with a few exceptions, “No matter which party is in power in almost any significant European country, they’re going to care a lot about climate change,” said Victor. “And that’s why Europe, frankly, for 25 years has been a reliable leader on international climate change policy.”

The findings also suggest that China and other non-democracies are expected to comply with their pledges not just because many of them have less ambitious pledges, but because they also have administrative and political systems that make it easier to implement national policies needed to align their countries with international commitments. 

“One of the challenges in democratic countries is that even if there’s strong political pressure to do something about climate, if a government is not well organized about it, then it very easily can make pledges that it can’t honor,” Victor said.

“There has been a lot of attention to ramping up ambition of the pledges,” he added. “There should be a lot more attention to getting countries to explain why their pledges are credible, and to assessing that credibility.”