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Secretary-General Antonio Guterres gave former New York mayor and billionaire media mogul Michael Bloomberg a new title Monday as U.N. special envoy for climate action, handing him the job of spurring speedy global action to help curb global warming.

A longtime activist for clean energy, Bloomberg was appointed U.N. special envoy on cities and climate change by then U.N. chief Ban Ki-moon in January 2014 and he has been traveling around the United States and the world to campaign for reducing climate-warming greenhouse gas emissions.

Guterres announced that Bloomberg will help support a U.N. Climate Summit that he is planning in 2019 to mobilize more ambitious action and start implementing the landmark 2015 Paris climate agreement now.

Countries agreed in the Paris accord to limit global warming to 2 degrees Celsius (3.6 degrees Fahrenheit) and do their best to keep it below 1.5 degrees C (2.7 degrees Fahrenheit), compared with pre-industrial times. But the agreement starts after 2020 — and at U.N. climate talks in November over 170 countries stressed the importance of implementing ambitious climate actions before 2020.

Speaking at a ceremony officially appointing Bloomberg to his new job, Guterres said temperatures in the atmosphere and at sea level are rising faster than expected, glaciers are receding more quickly, and the Arctic ice cap is "shrinking much more quickly and dramatically than in the past — so climate change is running faster than we are."

But there are two pieces of "very good news," the secretary-general said: "Today, the cheapest energy is green energy" and the "green economy" is the economy of the future. And there is "enormous capacity" to mobilize civil society, the business community and cities.

He pointed to the work Bloomberg has done in all those areas, saying: "I am very confident that this battle will be won, because the realities of today's economy are such that the wise decision is the green decision."

Guterres said last July that Bloomberg is "convinced" the United States will reach the Paris goals — despite President Donald Trump's decision to pull the U.S. out of the pact in 2020.

The former mayor has urged world leaders not to follow Trump.

"My hope is that President Trump listens to his advisers and looks at the data and changes his mind. And if that's the case, that shows a great leader who when facts change, and they recognize something different, they're not bound to what they did before, they're willing to change," Bloomberg said. "And I think it's fair to say this president does change his views — generally it's one day to the next."

Bloomberg has pledged to help save the Paris agreement. Last October, for example, his foundation donated $64 million to a Sierra Club program seeking to phase out coal-fired power plants and reduce planet-warming carbon emissions.

Bloomberg said Monday that his foundation is interested "in spending a lot of money in helping us understand that climate change is real and it's measurable."

As examples, he said that for the first time the North Pole in the middle of the winter had temperatures above melting, oceans over the last 20 or so years have risen, and there are more frequent and powerful storms. In addition, Bloomberg said, there are floods where there used to be droughts — and droughts where there used to be floods.

He said the solution is for people everywhere to get together and change the way they live, "and we have to be a little smarter about how we generate energy.