The U.S. and China just ratified the Paris climate agreement

The United States and China — two nations that have among the worst pollution records on earth — joined together in signing the Paris global climate agreement on Saturday.

The historic agreement is the world's first comprehensive global effort to reduce emissions, according to the BBC. 

The BBC also reported that the two countries — which represent the two largest economies in the world — contribute to a combined total of 40% of the world's carbon emissions. 

In order for the agreement to go into effect, 55 countries in total must add their signatures, and among them must produce a total of 55% of the world's carbon emissions. With the U.S. and China's signatures, the agreement has received a huge boon to that emissions target.

Although 180 nations signed the global climate pledge in December 2015, at the United Nations summit held in Paris, only 25 countries have formally ratified it thus far — a number that is expected to surge in September, Bill Hare, chief executive of Climate Analytics, told Reuters.

"The signal of the two large emitters taking this step together and taking it early ... should give confidence to the global communities and to other countries that are working on their climate change plans, that they too can move quickly and will be part of a global effort," Brian Deese, a senior Obama advisor, told reporters on Friday, according to Reuters.

During a speech in Hangzhou, China, U.S. President Barack Obama said that the agreement was the "single best chance that [we] have to deal with a problem that could end up transforming this planet," the BBC reported.

"We are moving the world significantly towards the goal we have set," he said.