Paris Climate Deal: US and China Formally Join Pact

The US and China - together responsible for 40% of the world's carbon emissions - have both formally joined the Paris global climate agreement.

After arriving with other leaders of G20 nations for a summit in the city of Hangzhou, Mr Obama said: "History will judge today's effort as pivotal."

CO2 emissions are the driving force behind climate change.

Last December, countries agreed to cut emissions enough to keep the global average rise in temperatures below 2C.

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