Environmental advocates are holding out hope that 150 world leaders and 40,000 delegates at climate talks—held in Paris on Nov. 30- Dec. 11—can reach a binding agreement to hold average global temperatures to an increase of less than 2° C, the level scientists say is necessary to prevent irreversible changes to the earth’s ecosystems. But Republicans in Congress may present obstructions.

At the opening of the “Conference of Parties 21,” President Obama said he is looking for “an enduring framework for human progress—not a stopgap solution, but a long-term strategy that gives the world confidence in a low-carbon future.” He added that world leaders need to show they are serious about reducing carbon emissions. “There are hundreds of billions of dollars ready to deploy to countries around the world if they get the signal that we mean business this time,” he said.