President Xi Jinping’s surprise announcement that China plans to go carbon-neutral by 2060 has left many questions, none more important than: “How?” China is the world’s largest energy user and greenhouse gas emitter, mines and burns half the world’s coal, and is the top importer of oil and natural gas. Transitioning that economic behemoth to carbon-neutrality within a few decades could cost $5.5 trillion, Sanford C. Bernstein & Co estimates, and require the deployment of technologies that are barely in use today.

“What’s being contemplated here has never been done before,” said Neil Beveridge, an analyst at Bernstein. “The larger the energy mix, the longer it takes to transition. This is a monumental challenge.” While Xi’s comments during his speech to the United Nations on Tuesday were void of details, he did said China would scale up its Paris Agreement commitments through “more vigorous” measures. China may provide more details about its new climate strategy in an official submission to UN later this year, said Chai Qimin, a government researcher affiliated with the Ministry of Ecology and Environment.

“If any country can achieve such ambitious goals it will be China,” said Gavin Thompson, Asia-Pacific vice-chairman at consultancy Wood Mackenzie Ltd. “Strong state support and coordination have proved extremely effective at reaching economic goals; if this is now directed towards climate change then China is capable in transforming its carbon emissions trajectory over the coming four decades in exactly the same way it has transformed its economy over the past 40 years.”

Renewable Energy

Non-fossil fuels, which account for about 15% of the country’s primary energy mix now, will have to take a huge leap forward. China had about 213 gigawatts of solar and 231 of wind power capacity installed at the end of last year, according to BloombergNEF. That will have to increase to at least 2,200 gigawatts of solar and 1,700 of wind by 2060 to make the transition, said Xizhou Zhou, vice president for global power and renewables at IHS Markit Ltd.