The format meant a cavalcade of short speeches by world leaders,some scripted,some apparently more impromptu. “This is not bunny-hugging,” British Prime Minister Boris Johnson said of the climate efforts. “This is about growth and jobs.”

The Biden administration’s pledge would require by far the most ambitious US climate effort ever,nearly doubling the reductions that the Obama administration had committed to in the landmark 2015 Paris climate accord.

The new urgency comes as scientists say that climate change caused by coal plants,car engines and other fossil fuel use is already worsening droughts,floods,hurricanes,wildfires and other disasters and that humans are running out of time to stave off most catastrophic extremes of global warming.

But administration officials,in previewing the new target,disclosed aspirations and vignettes rather than specific plans,budget lines or legislative proposals for getting there.

Biden planned to join a second session of the livestreamed summit later in the morning on financing poorer countries’ efforts to remake and protect their economies against global warming.

With the pledge from the US and other emissions-cutting announcements from Japan,Canada,the European Union and the United Kingdom,countries representing more than half the world’s economy will have now committed to cutting fossil fuel fumes enough to keep the earth’s climate from warming,disastrously,more than 1.5 degrees celsius,the administration said.

As of 2019,the last year before the pandemic,the US had reduced 13 per cent of its greenhouse gases compared with 2005 levels,which is about half way to the Obama administration goals of 26 to 28 per cent,said climate scientist Niklas Hohne of Climate Action Tracker. That’s owing largely to market forces that have made solar and wind,and natural gas,much cheaper

Biden,a Democrat,campaigned partly on a pledge to confront climate change. He has sketched out some elements of his $US2 trillion ($2.6 trillion) approach for transforming US transportation systems and electrical grids in his campaign climate plan and in his infrastructure proposals for Congress.

His administration insists the transformation will mean millions of well-paying jobs. Republicans say the effort will throw oil,gas and coal workers off the job. They call his infrastructure proposal too costly.

“The summit is not necessarily about everyone else bringing something new to the table – it’s really about the US bringing their target to the world,” said Joanna Lewis,an expert in China energy and environment at Georgetown University.

Political divisions in America that were exposed by Trump’s presidency have left the nation weaker than it was at the 2015 Paris accord. Unable to guarantee that a different president in 2024 won’t undo Biden’s climate work,the Biden administration has argued that market forces – with a boost to get started – will soon make cleaner fuels and energy efficiency too cheap and consumer-friendly to trash.

Having the US,with its influence and status,back in the climate game is important,said Lauri Myllyvirta,lead analyst at the Centre for Research on Energy and Clean Air in Helsinki.

But hoping the world will forget about the last four years seems like wishful thinking,he said.

“There is too much of an impulse in the US to just wish away Trump’s legacy and the fact that every election is now basically a coin toss between complete climate denial and whatever actions the Democrats can bring to the table,” he said.

AP