Major climate news arrived on Tuesday when Chinese President Xi Jinping said China would aim for "carbon neutrality" by 2060 and a CO2 emissions peak before 2030.

Why it matters: China is by far the world's largest greenhouse gas emitter. So its success or failure at reining in planet-warming gases affects everyone's future.

The big picture: Glen Peters of the Center for International Climate Research said the 2060 goal — if it happens — keeps alive the prospect of holding global temperature rise to 1.5°C.

• That's the most ambitious and moonshot goal of the Paris climate deal and it's fast slipping out of reach.
• And here's Wood Mackenzie analyst Alex Whitworth in a note this morning: "The world’s largest carbon emitter finally shifted from its long-term position of having limited responsibility to reduce global emissions as a developing country, to assuming clearer leadership in tackling climate change."

Catch up fast: Xi made the pledge in video remarks Tuesday before the UN General Assembly.

• He also said China will slightly toughen its nearer-term pledge under the Paris deal by aiming for the emissions peak before 2030. Their current pledge said they'll do this "around" 2030.

Reality check: The new commitment is very brief and super vague and there's no guarantee they will make good.

• China watchers are now looking to see how the country will define "carbon neutrality" and what concrete steps it's planning to transform the targets into action.
• "China’s upcoming 14th five-year plan has the potential to be the most important document in global energy market history," Gavin Thompson, another Woodmac analyst, said in their note.
• And, here's just one of many challenges: China's fleet of coal-fired power plants is very young and they're still building new ones.

The intrigue: Xi's speech came after President Trump's remarks hit China for "rampant" pollution, touted his decision to abandon Paris, and noted the U.S. has reduced CO2 emissions.

• "Xi Jinping’s climate pledge at the UNGA, minutes after Trump’s speech, is clearly a bold and well calculated move. It demonstrates Xi’s consistent interest in leveraging the climate agenda for geopolitical purposes," says Greenpeace's Li Shuo.