UPDATE 1-U.S. envoy Kerry calls for climate change measures to be speeded up

(Adds comments, background)

MILAN, Jan 21 (Reuters) - U.S. special climate envoy John Kerry said on Thursday measures to tackle climate change needed to be ramped up significantly, and achieving net zero global carbon emissions by 2050 would require a radical transformation of the economy.

“Failure at the COP (climate conference) in Glasgow is not an option,” Kerry said in an online event organised by a business forum linked to Italy’s presidency of the G20.

New Democratic President Joe Biden named former Secretary of State Kerry as special climate envoy back in November, a sign that he was putting climate change at the centre of his foreign policy.

Kerry said coal needed to be phased out five times faster than is the case at present while renewable energy needed to be ramped up six times faster and electric car roll-out 22 times.

“We must move from the dirtier options much faster ... we have to reach a much faster path of decarbonisation ... it is doable,” he said.

Biden, who was sworn in as president on Wednesday, has promised to put the United States on a track to net-zero emissions by 2050 with climate change one of his key priorities.

On Wednesday he re-committed to rejoining the 2015 Paris climate accord that his predecessor Donald Trump withdrew from, claiming it was too costly to the U.S. economy.

“(In) the last 4 years the leader of our country chose to pull out of the agreement and engage in reckless behaviour with respect to the future of people all over the world,” Kerry said.

Reporting by Stephen Jewkes, additional reporting by Valentina Za, editing by Giles Elgood