Praising the passion and articulacy of the assembled young climate activists, he urged them to demand action from their politicians and business leaders ahead of the Cop26 summit in Glasgow at the end of this month.
He said they were justified in feeling frustrated “with those who aren’t doing enough to stop” global warming, but did not respond directly to criticism levelled at him personally by Ms Thunberg earlier this week.
She used a speech at the conference on Tuesday to ridicule global leaders over their rhetoric on tackling global warming, saying: “Build back better. Blah, blah, blah. Green economy. Blah blah blah. Net zero by 2050. Blah, blah, blah.
“This is all we hear from our so-called leaders. Words that sound great but so far have not led to action. Our hopes and ambitions drown in their empty promises.”
The 18-year-old Swedish activist quoted Mr Johnson saying the green agenda was “not some expensive, politically correct, green act of bunny hugging”, as she warned that science does not lie.
It’s dire, but change is possible, says PM
The UN predicts that carbon emissions are set to rise by 16 per cent by 2030, while the target of keeping global warming under the internationally agreed ceiling of 1.5C requires that they fall by half.
Ms Thunberg said Britain’s new licences and drilling permissions for oil and gas in the North Sea are “textbook examples of hypocrisy”, as the UK prepares to host the Cop26 summit.
Research published this week shows that a child born in 2020 will endure seven times as many extreme heatwaves and twice as many droughts as their grandparents.
Mr Johnson told the young activists: “Hundreds of millions of you are facing rising seas, failing crops, burning forests and ever more ferocious storms. Daily challenges that lead to lost opportunity.”
He said the current situation is “dire” and “frightening”, but added: “Change is possible and it can be done.”