While the number of climate laws and policies worldwide has increased dramatically over the past 20 years, from just 72 in 1997 to 1,500 today, the pace of passing new legislation has recently significantly slowed, according to a new study.

From the years 2009 to 2015, between 100 and 143 climate change laws were passed globally every year. That number dipped in 2016 to 64, and then again dropped last year to just 36, according to the study, which was published this week by the Grantham Research Institute on Climate Change and the Environment, and the ESRC Centre for Climate Change Economics and Policy at the London School of Economics and Political Science.

While having a body of existing policies and laws that cover "substantial ground" lessens the need for new legislation, "a sustained low level of legislative developments could be a sign for concern," the study says.

The report was published on Monday as diplomats and environmentalists gathered in Bonn, Germany, to keep working on the rules governing the 2015 Paris climate accord, a landmark agreement aimed at combating climate change. Among the unresolved issues are how to ensure transparent monitoring of what countries do to cut global emissions and the methods used take stock of what countries have achieved. Advocates also want governments at the two-week talks to explicitly acknowledge that current national pledges won't be enough to keep global warming below 2 degrees Celsius by 2100, and therefore raise their ambitions.

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The talks are part of preparations for December's global climate summit in Katowice, Poland, when the so-called Paris rulebook must be formally approved.

While President Donald Trump announced last year that the U.S. will pull out of the Paris accord, the rest of the world remains committed to the deal.

The study published this week found that all 197 countries, nations and territories that have signed or ratified the Paris Agreement have at least one policy or law on climate change or "the transition to a low-carbon economy." Of the 1,500 climate laws and policies in place around the world today, 106 of them were introduced since the Paris Agreement was reached in December 2015, and 28 of those specifically reference it.

The report notes, however, that "further analyses will be required to determine if these new laws and policies are consistent with the Paris Agreement and countries' nationally determined contributions."

"Alignment between national and international goals will be pivotal to meeting the Paris targets," it says.