The US was one of the 196 countries that adopted a climate agreement on Saturday, which took the shape of a 133-page rulebook for implementing the landmark 2015 Paris climate change negotiations. The Katowice deal from the United Nations talks signals that the world should step up its ambitions beyond current pledges—which are far from adequate to contain warming to under a disastrous 2 degrees Celsius—when the Paris agreement kicks into effect in 2020. Negotiators with the UN Climate Action summit ended up with a deal that was a mixed bag of ambition and unresolved issues.