Why is John Kerry stepping down as US climate envoy?

John Kerry, the United States climate envoy who has been instrumental in the Biden administration's efforts to combat climate change, is set to step down from his position to focus on the president's reelection campaign, US media reported Saturday.

Ex-US secretary of state and senator Kerry has been working with other countries to increase climate change commitments, including at the 28th Conference of the Parties (COP28) summit in Dubai, AFP reported.

He plans to support Biden's campaign by publicising his efforts in combating global warming, according to US media outlets.

Kerry informed Biden of his intentions to leave on Wednesday, and his staff learned of the decision on Saturday, officials said.

Besides leading the US delegation at three UN climate summits, Kerry worked effectively with China despite complicated diplomatic relations. The countries are the world's two largest polluters, accounting for 41% of greenhouse gas emissions.

In a rare display of unity, the US and China helped carry the COP28 December climate summit in Dubai, where negotiators sealed a historic although watered-down agreement to begin to transition away from oil, gas and coal.

Kerry had welcomed his Chinese counterpart Xie Zhenhua a month earlier in California, where the two countries agreed on outlines of climate action that partly served as a basis for the nearly 200-nation Dubai deal.

Biden's first act after his inauguration was to rejoin the Paris Climate Agreement, which aimed to limit Earth's warming to "well below" 2°C. However, 2023 was the hottest on record, with the increase in Earth's surface temperature nearly crossing the 1.5°C threshold, according to Europen Union (EU) climate monitors.

Kerry, himself a one-time Democratic presidential nominee, will step down sometime in the coming months, according to Axios, which first reported the news.