This week the Prime Minister announced a “world-leading” target for the UK to cut emissions by 78 per cent on 1990 levels by 2035, which builds on plans to cut pollution by 68 per cent by 2030, the most ambitious among leading economies.
But environmental groups in the UK have warned that policies and action are urgently needed to deliver on the pledges and cut pollution from homes, transport, industry and power supplies.
Addressing the summit, the Mr Johnson said climate action was not an “expensive, politically correct, green act of bunny hugging” but could deliver green jobs and growth, and the world could build back better from the pandemic by building back greener.
“Let’s use this extraordinary moment and the incredible technology that we’re working on to make this decade the moment of decisive change in the fight against climate change and let’s do it together,” he urged.
In response Ms Thunberg, who rose to fame for leading international school strikes, changed her biography on Twitter to "bunny hugger".
The Swedish activist has previously changed her description in response to politicians’ comments.
In 2019, after then US President Donald Trump said she had an anger management problem and needed to chill, Ms Thunberg changed her description to: "A teenager working on her anger management problem. Currently chilling and watching a good old fashioned movie with a friend".
Watch: Greta Thunberg changes Twitter bio to 'bunny hugger' after Boris Johnson's climate summit remarks
Mr Biden and Boris Johnson, who also addressed the summit, both sought to highlight the opportunity to create good jobs from shifting to clean energy and technology as they urged other countries to follow their lead with action.
The two-day summit on Earth Day also heard from leaders from major economies including China, Brazil, Russia and India – with countries including Japan and Canada announcing more ambitious goals to cut emissions in the next decade.
Countries are under pressure to come forward with more ambitious plans up to 2030, under the global Paris Agreement, ahead of a major UN summit, Cop26, taking place in November.
That is because existing plans are not nearly enough to meet countries’ commitments under the Paris deal, which aims to curb global temperature rises to as little as 1.5C if possible and avoid the most dangerous impacts of climate change
Mr Johnson also focused on the role new technology, including carbon storage tech, new crops and cheap hydrogen, could play to tackle the climate crisis, as he welcomed the US’s “game-changing” announcement and highlighted UK action.
“As host of Cop26 we want to see similar ambitions around the world, we are working with everybody from the smallest nations to the biggest emitters to secure commitments that will keep change to within 1.5C.
“I think we can do it, to do it we need scientists in all of our countries to work together to produce the technological solutions that humanity is going to need,” he said.
He also highlighted the need for rich nations to go beyond existing commitments to deliver 100 billion US dollars a year in finance to support developing countries to tackle the climate crisis.
Watch: World leaders, activists & pope make Earth Day appeals