The news follows widespread backlash after No.10 said Sunak would not be attending as he focused on the autumn budget, which was due to be published on 31 October but has been pushed back to 17 November.
Sunak has now confirmed that he will be attending the conference, tweeting that there would be "no long-term prosperity without action on climate change" or energy security without investing in renewables.
"That is why I will attend COP27P next week: to deliver on Glasgow's legacy of building a secure and sustainable future."
Alok Sharma, lead of last year's Conference of The Parties (COP) which was held in Glasgow, said that Sunak’s attendance would send a signal about “our renewed commitment on this issue”.
Green MP Caroline Lucas said she was "glad to see Sunak’s screeching U-turn" and described his back-and-forthing as "an embarrassing mis-step on the world stage".
Shadow climate change and net sero secretary Ed Milliband said Rishi Sunak’s original decision not to attend showed that he “just doesn’t get it when it comes to climate change and energy issues”, and said that the “storm of criticism” has been key to his u-turn.
On Tuesday, former prime minister Boris Johnson confirmed that he will also be attending COP27, as did Scotland first minister Nicola Sturgeon. King Charles will not attend the summit.
America’s President Joe Biden will also reportedly be attending, despite the summit coinciding with the US Midterms elections next month. Swedish environmental activist Greta Thunberg has said she will not be attending COP27, criticising the Egyptian government for gatekeeping, greenwashing, and describing the COP as “an opportunity for leaders and people in power to get attention”.
Sarah Mukherjee MBE, chief executive officer of the Institute of Environmental Management and Assessment, said: "The Prime Minister's decision to attend the climate negotiations is a positive one.
"With other world leaders expected to be in attendance it is an opportunity for the UK to play a leadership role in ensuring that COP27 delivers an ambitious set of outcomes that limit global warming to below 1.5C."
Friends of the Earth International climate campaigner Rachel Kennerley said: “It would have been a remarkable own goal for the Prime Minister to miss this year’s UN climate talks as the UK’s own presidency draws to a close, so it’s good that he’s seen sense and decided to attend.
“But simply showing up won’t be enough. The UK government has a lot of work to do to rebuild its climate reputation after a year of rowing back on commitments made in Glasgow."