Joe Biden has warned world leaders this is the "decisive decade" to avoid the worst of the climate crisis as he outlined targets for the US to halve its emissions by 2030.
The US president announced a new target to achieve a 50-52% reduction in emissions from 2005 levels by 2030, as he hosted a virtual leaders summit to galvanise international action to curb rising global temperatures.
Mr Biden and British Prime Minister 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.
Ireland is being represented by Minister for the Environment, Climate and Communications Eamon Ryan.
The Government made a commitment to "pursue and achieve" carbon neutral status for Ireland by no later than the end of 2050 in the Climate Action Bill published last month.
Mr Ryan was due to take part in a discussion on climate adaptation and resilience chaired by US Agriculture Secretary Tom Vilsack.
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 to curb global temperature rises to as little as 1.5C if possible and avoid the most dangerous impacts of climate change.
In the wake of the announcements at the summit, environmental and aid campaigners warned much more ambition was needed to meet the 1.5C goal and action and policies had to deliver on the targets.
And Cop26 President Alok Sharma said the warning lights were "flashing bright red" as planet Earth faced make or break in the next decade.
He said the global community had not yet done enough to meet the goals of the Paris Agreement, as he urged countries to take immediate action to meet targets set out in their national plans, for example by phasing out coal.
The new US target is part of its national climate plan, being submitted as part of its return to the Paris accord, the world's first comprehensive climate treaty which Donald Trump quit when he was president.
Analysts at Climate Action Tracker said the new US target would reduce the global emissions gap between action pledged and the cuts needed to meet the Paris goals by around 5-10% in 2030, but bigger cuts would be needed for the US to play its part in meeting the 1.5C target.
Opening the summit, Mr Biden said the US was resolved to take action, but could not solve the problem on its own, urging: "All of us, particularly those who represent the world's largest economies, we have to step up.
"Those that do take action and make bold investments in their people, in clean energy futures, will win the good jobs of tomorrow and make their economies more resilient and more competitive."
And he warned: "Scientists tell us that this is the decisive decade. This is the decade we must make decisions that will avoid the worst consequences of the climate crisis.
"We must try to keep the Earth's temperature to an increase of 1.5C," he said, warning a world beyond 1.5C meant more frequent and intense fires, floods, droughts, heatwaves and hurricanes hitting communities, lives and livelihoods.
This week Mr Johnson announced a "world-leading" target for the UK to cut emissions by 78% on 1990 levels by 2035, which builds on plans to cut pollution by 68% 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 PM 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.
He 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.
The summit comes after the International Energy Agency warned that global carbon emissions were set for their second biggest increase on record after a sharp drop in 2020 due to the pandemic, with demand for fossil fuels, including coal, pushing climate pollution up to close to 2019 levels.
It also heard from UN secretary general Antonio Guterres, who called for action including ending subsidies for fossil fuels, ramping up investments in renewable energy, an end to coal power plants and for finance to help developing countries develop cleanly and deal with the impacts of climate change.
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Countries announce climate targets
Yesterday, European lawmakers in Brussels reached a last-minute agreement with members states on a net reduction of "at least 55%" of greenhouse gas emissions by 2030.
Meanwhile, Australia will spend A$565.8 million (€364 million) to co-fund research and pilot projects in green technologies, Prime Minister Scott Morrison has said, as his country seeks to illustrate its commitment to reducing carbon emissions.
While Mr Morrison has resisted global calls to commit to a target of net zero emissions by 2050, citing the risk of damage to Australia's economy, he promised the co-investment with partners from the UK, Japan, South Korea and Germany.
"Getting new energy technologies to parity will enable substantial reductions in global emissions - in both developing and developed countries - and ensure countries don't have to choose between growth and decarbonisation," he said in a statement.
"But Australia won't be able to make these technologies globally scalable and commercially viable all on our own."
Mr Morrison said international partners will invest between three and five times the amount Australia will spend on the research and pilot programmes.
The spending, which will be allocated from Australia's budget to be unveiled next month, is the latest outlay to be revealed from Canberra's A$18 billion (€11bn) fund established to invest in low-emission technology to meet its climate pledges.
Climate activists shatter windows at HSBC HQ in London
Climate activists shattered at least 19 windows at HSBC's headquarters in London's Canary Wharf as part of a protest against the financing of what the group says is devastating climate change that threatens the planet.
The activists from the Extinction Rebellion group used hammers to break the windows and pasted stickers on the windows before sitting down to wait for the police to arrive, a Reuters reporter at the scene said.
"Despite HSBC's pledge to shrink its carbon footprint to net zero by 2050, their current climate plan still allows the bank to finance coal power, and provides no basis to turn away clients or cancel contracts based on links to the fossil fuel industry," Extinction Rebellion said.
A spokesman for HSBC declined to make an immediate comment.
Police said that nine people had been arrested.
Extinction Rebellion wants to trigger a wider revolt against the political, economic and social structures of the modern world to avert the worst scenarios of devastation outlined by scientists studying climate change.
"It's time to stand up and be counted," said Gully Bujak from the group.
"Doing this today may land us in prison but we're on the right side of history."
The activists referenced the struggle of the Suffragettes who used direct action to fight for votes for women in the early 20th century.
The group broke windows at the London headquarters of Barclays two weeks ago.
Additional reporting Brian O'Donovan, AFP, Reuters