Envoys from almost 200 nations gathered in Poland's southern city of Katowice, a day earlier than originally planned, for the UN meeting that's scheduled to run until December 14. Ministers and some heads of government joined in on 3 December . Host Poland will push for a joint declaration to ensure a "just transition" for fossil fuel industries like coal producers who are facing closures as part of efforts to reduce greenhouse gas emissions. The meeting received a boost over the weekend, after 19 major economies at the G-20 summit affirmed their commitment to the 2015 Paris climate accord. The only holdout was the United States, which announced under President Donald Trump that it is withdrawing from the climate pact.