Philanthropist and former U.S. presidential candidate Michael Bloomberg is rejoining the United Nations as its special envoy on climate ambition and solutions. U.N. Secretary-General António Guterres said Friday that Bloomberg will work “to mobilize stronger and more ambitious climate action in the lead-up to the critical Glasgow Climate Conference – COP 26 – in November 2021.”That gathering is the annual review conference for the 2015 Paris Climate Agreement, which aims to reduce global greenhouse gas emissions and limit the planet’s temperature increase. The United Nations says bold commitments are needed to keep the global temperature increase to below 2 degrees Celsius this century.A long-time climate activist, Bloomberg was Guterres’ special envoy for climate action from March 2018 until November 2019, when he made a late entry into the presidential race as a Democratic candidate. Under the previous U.N. chief, Ban Ki-moon, he was U.N. special envoy for cities and climate change.The U.N. said Bloomberg will support the secretary-general in expanding and strengthening the coalition of governments, cities and companies committing to reach net-zero carbon emissions by 2050. Bloomberg’s own company pledged this week to meet that target by 2025.Today, Bloomberg LP commits to achieving net-zero carbon emissions by 2025. Companies have a key role to play in fighting climate change, and @Bloomberg is committed to helping lead the way. https://t.co/5LUbWyaYLwhttps://t.co/XOfmxngsyF— Mike Bloomberg (@MikeBloomberg) February 3, 2021“The Special Envoy will engage government officials and members of the private sector and civil society to finalize and implement plans, particularly in high-emitting countries, industries and sectors, to vastly accelerate the transition to a clean energy economy,” the statement announcing his appointment said.Guterres has also called for the phasing out of coal plants in industrialized nations by 2030, and in other nations by 2040 — a goal Bloomberg supports.Great news on climate action from Europe: The EU’s foreign ministers are putting their policy weight behind supporting an end to coal. Our @EurBeyondCoal campaign has already closed 154 plants since 2016, and this will help accelerate progress. https://t.co/jySY1AjFx6— Mike Bloomberg (@MikeBloomberg) January 25, 2021The former three-time New York City mayor is also board president of the C40 Cities Climate Leadership Group, a global network of 97 major cities, and co-chair of the Global Covenant of Mayors for Climate & Energy, a network of more than 10,000 cities and local governments. In addition to climate action, Bloomberg has put billions of dollars into other issues, including public health and gun safety. The World Health Organization announced Wednesday that he will continue for a third term as the agency’s global ambassador for noncommunicable diseases and Injuries.