Greta Thunberg mocked Boris Johnson as she opened a climate summit in Italy today - accusing them of making 'empty promises' over global warming. Quoting a speech that Mr Johnson gave back in April, she said: 'This is not about some expensive politically correct dream of bunny hugging, or build back better, blah blah blah. Green economy, blah blah blah, net zero by 2050, blah blah blah.' Thunberg, who rose to fame thanks to her 'school strike for climate' protests in her native Sweden, then added: 'This is all we hear from our so-called leaders.