Natural history expert Sir David Attenborough has said "we can't be radical enough" in combating climate change.
Answering questions from British MPs at a UK parliamentary committee on Tuesday, the 93-year-old warned that "great social unrest" could be approaching in the next two or three decades.
It will affect "what we eat, how we live, and so on. It's going to happen," he said.
Attenborough opened the session by recalling his most vivid memory of seeing climate change occur at the Great Barrier Reef.
He said: "I will never forget diving on the reef around 10 years ago, but instead of seeing this multitude of wonderful forms of life, it was stark white.
"It had bleached white because of the rising temperatures and increasing acidity of the sea."
Referring to his decades of experience presenting nature programmes, Attenborough said half of a century earlier "we never thought humans could change the climate".
"We now know we are, and what is worse is that we're changing it in a way that is irreversible if we go on the way we are."
Tuesday's hearing was held as part of the UK's clean growth strategy, which aims to decarbonise the nation.
In June, outgoing Prime Minister Theresa May committed the UK to reduce its carbon emissions to net zero by 2050, becoming the first G7 country to make such a pledge.
Attenborough said he didn't know whether the 2050 target was practical, but added that he believed it also wasn't the way to look at the issue.
"We can't be radical enough in dealing with these issues. The question is what is possible, how can we take the electorate with us."
"Dealing with the problems means changing our lifestyles," he added.
He later laid the blame at the UK's door, saying the industrial revolution had begun the motion toward a changing climate, and that it was "only a right and responsible" thing for the UK to also lead on solving such issues.
Looking to the younger electorate, he said he found it "a great source of comfort" that the youth were "making their voices very clear" on climate, before saying he hoped people would continue to make their voices heard to world leaders.
He also took aim at US President Donald Trump over moves to withdraw from the Paris climate accord.
He said: "It'll be a very sad day if he succeeds.
When asked about his opinion on climate change deniers, Attenborough referred to Trump once more: "I am sorry there are people who are in power internationally - notably, of course, the United States, but also in Australia which is extraordinary actually because Australia is already having to deal with some of the most extreme manifestations of climate change - both Australia and America, those voices are clearly heard."
"And one hopes that the electorate will actually respond to those.”
Trump has, in the past, said he believed climate change was an elaborate "hoax" set up by China.
But on a positive note, Attenborough said: "The only way you can get up in the morning is to believe that, actually, we can do something...and I believe that we can."