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British naturalist Sir David Attenborough has urged COP26 climate summit delegates to "turn tragedy into triumph" and tackle climate change.
In an impassioned speech which drew a standing ovation, he said the fate of future generations must give delegates the impetus "to rewrite our story".
The 95-year-old warned that humanity was "already in trouble" because of rising carbon levels in the atmosphere.
More than 120 world leaders are in Glasgow for the two week summit.
The COP26 conference is seen as crucial to limit global temperature increases, and changes to the climate.
The world is now about 1.2C warmer than it was in the 19th Century – and extreme weather events like heatwaves, floods and forest fires are already becoming more intense.
The 2015 Paris climate conference called for average temperatures to rise by well below 2C, and preferably only 1.5C, when compared to pre-industrial averages.
But unless more is done, the planet is already on track to warm by more than 2C by the end of this century.
'The greatest problem solvers'
Sir David spoke for seven minutes alongside screens showing a graph that tracked the rise of carbon concentration in the Earth's atmosphere.
That number – which Sir David said was "the clearest way to chart" the story of humanity – currently sits at close to 414 parts per million. According to the Greenhouse Gas Bulletin, that is now 149% of the pre-industrial level.
"Our burning of fossil fuels, our destruction of nature, our approach to industry, construction and learning, are releasing carbon into the atmosphere at an unprecedented pace and scale," he told the conference. "We are already in trouble."
He also criticised wealthier nations, saying this was also a story of inequality and that "those who've done the least to cause this problem are being the hardest hit."
The naturalist however said people were "the greatest problem solvers to have ever existed on Earth" and called on leaders to think of the younger generation as they work to address climate change.
"If working apart we are a force powerful to destabilise our planet, surely working together we are powerful enough to save it," he said, before concluding, "In my lifetime I've witnessed a terrible decline. In yours, you could and should witness a wonderful recovery."
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World leaders give first speeches to summit
His address came after a strongly worded speech from UN Secretary General António Guterres. Demanding that people stop "treating nature like a toilet" he sharply criticised continued use of fossil fuels, saying "we are digging our own graves".
UK Prime Minister Boris Johnson said future generations "will judge us with bitterness" if they failed at the conference, while US President Joe Biden said that "none of us can escape the worst of what's yet to come if we fail to seize this moment".
Mr Biden was among those delegates to give a standing ovation to Sir David Attenborough's speech.
But outside the conference on the streets of Scotland's largest city, activists and protesters demanded more from global leaders.
Teenage campaigner Greta Thunberg told a crowd of demonstrators that politicians at the summit are "pretending to take our future seriously".
"Change is not going to come from inside there. That is not leadership. This is leadership. This is what leadership looks like," she said to cheers.
The climate summit is set to run for two weeks until 14 November.
Image source, PA MediaImage caption, Greta Thunberg told demonstrators outside the conference that politicians were "pretending to take our future seriously"