An international agreement to limit hydrofluorocarbons (HFCs) is a significant step forward in the effort to slow global warming, several leading climate scientists say, but it will fall far short of politicians' lofty promises.

Government leaders have touted the deal as a method to reduce global temperatures by as much as 0.5° Celsius by 2100, citing research that showed the emission from air conditioners trapped thousands of times more heat in the atmosphere than carbon dioxide.

"Agreeing a deal to phase down the use of HFCs is the single most important step we can take to limit the warming of the planet," U.S. Secretary of State John Kerry said Thursday from Kigali, Rwanda, where the deal was reached early Saturday.

Indeed, the Paris climate accord calls for warming to be limited to 1.5º Celsius, and so a reduction of 0.5° would be an enormous step toward meeting that goal.

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But "[e]ager to declare a victory, governments glossed over many uncertainties about HFCs," Reuters reports.

"Some more recent research indicates HFCs may be less powerful in trapping heat than once feared," Michiel Schaeffer of Climate Analytics told the wire service. Climate Analytics is a European research organization that projects warming based on governments' climate pledges.

"My guesstimate would be around 0.2 degree Celsius (0.36F) by 2100" of avoided warming as a result of the agreement, Schaeffer told Reuters.

Reuters adds:

Guus Velders, an author of the widely quoted 2013 study of HFCs and warming, said his calculations of the impact of the Kigali accord show HFCs are now likely to stoke only 0.06C (0.1F) of warming this century, down from a range of 0.3C to 0.5C with no action.

Andrew Jones of Climate Interactive, a U.S. based think-tank that builds climate simulations, also said that while the HCF agreement was a significant step, "it's in no way a silver bullet."

Climate Interactive currently predicts that the Paris accord will lead to a staggering 3.5ºC of warming by the end of this century. Jones told Reuters that he will not reduce that prediction by 0.5ºC as a result of the HFC deal.

Small island nations had pushed particularly hard for quick international action to limit HFCs, as they are already suffering from rising sea levels caused by climate change—and leaders acknowledged that while the agreement isn't perfect, is still a "good deal."

"It may not be entirely what the islands wanted, but it is a good deal," the minister-in-assistance to the president of the Marshall Islands, Mattlan Zackhras, told the Guardian. "We all know we must go further, and we will go further."