A host of famous faces from around the globe have been spotted in Glasgow at the Cop26 climate summit.
Along with world leaders, including US president Joe Biden and prime minister of Canada Justin Trudeau, members of the Royal Family are in attendance as well as special guest natural historian Sir David Attenborough.
But another high-profile name on the guest list is former president of the United States Barack Obama.
Mr Obama, the 44th US president, confirmed his attendance at the climate conference back in October.
His spokesperson said he would be laying out "the important progress made in the five years since the Paris Agreement took effect".
Cop26 is being billed as a critical moment in the climate crisis as leaders are being urged to act on promises made in Paris and commit to further action in a bid to keep rising temperatures to a 1.5C target.
Mr Obama is yet to be seen at Cop26, which is taking place at the SEC in Glasgow between October 31 and November 12, but it is understood he will be attending at a later date.
The Obama Foundation said the former president would participate in a roundtable discussion with emerging leaders on Monday, November 8.
It said Mr Obama will sit down with a small group from around the world to discuss how young people can make their voices heard in the climate debate and spark further action.
According to CNN, sources close to Mr Obama say his appearance is intended to help President Biden win back faith in American leadership on the issue of climate change, following Mr Trump's presidency.
Mr Biden flew into Edinburgh on Air Force One before his multi-vehicle motorcade was spotted on the M8 heading towards Glasgow for the start of the conference on Monday.
Addressing world leaders on the first day of Cop26, Mr Biden said the US was "back at the table" ready to take a leading role in combating climate change.
His predecessor Mr Trump had withdrawn the US from the 2015 Paris climate pact during his time in office.
Mr Biden told the conference: “I shouldn’t apologise, but I do apologise for the fact the United States, the last administration, pulled out of the Paris Accords and put us sort of behind the eight ball a little bit.”
The president acknowledged that the US and other developed nations bear much of the responsibility for climate change, and said actions taken this decade to contain global warming will be decisive in preventing future generations from suffering.
“None of us can escape the worst that is yet to come if we fail to seize this moment,” he told the conference.
Mr Obama said the signing of the Paris Agreement was one of his "proudest moments" of his presidency.
In a video posted on his Twitter page, the former president reflected on the signing of the Paris accord and what it meant for the climate change crisis.
"We all knew that Paris by itself does not solve the climate crisis," he said. "But our basic assumption was that once we got everyone signed on, then with each successive year we could try to negotiate for greater and greater reductions.
"Now you have cities and corporations, the nonprofit sector, all working to continue moving the boulder up the hill and I am optimistic."
"We have no time to lose and we have to take this seriously," he added.
On Monday, broadcaster and natural historian Sir David Attenborough, who has been named the Cop26 People's Advocate, addressed world leaders at the global climate summit.
The 95-year-old warned humanity is “already in trouble” due to burning fossil fuels, destroying nature and releasing carbon into the atmosphere, and said those least responsible were being hardest hit.
“Perhaps the fact that the people affected by climate change are no longer some imagined future generations but young people alive today, perhaps that will give us the impetus we need to rewrite our story, to turn this tragedy into a triumph," he said.
