World leaders made a climate pledge on coal and recognized the importance of reaching carbon neutrality ‘by or around mid-century’ on the final day of the G20 summit in Rome. Meanwhile, the United Nations’ climate summit COP26 officially began in Glasgow, Scotland amid dire warnings by scientists on the time left to cap global warming to 1.5 celsius. New York Times climate reporter Somini Sengupta joins. COP26 marks the 26th "conference of parties," or all the countries that have signed on to international climate change action starting with the UN Framework Convention on Climate Change and later the Paris Agreement. The Paris Agreement was the last major international agreement on climate change designed to reduce key countries' greenhouse gas emissions to keep global average temperatures from rising 2 degrees celsius or more. It was adopted in 2015. The G20 or "group of 20" is a forum for diplomacy and economic agreements made up of the 19 largest national economies and the European Union (economic and political alliance of European countries). The forum represents leadership of two-thirds of the world population and more than 75% of international trade.