The US has unveiled an updated carbon pledge that will see its emissions nearly halved by 2030
President Joe Biden will host 40 leaders at a virtual summit in the White House to raise ambition on tackling climate change
The meeting will aim to re-assert US global leadership in the area after President Trump pulled the country out of the Paris agreement
President Biden has made the climate a key focus for his administration, re-joining the Paris agreement on his first day in office
Ahead of the meeting, officials urged greater ambition, particularly among countries perceived as "laggards" on climate
The leaders of China, the UK, India, Canada, France, Germany, South Africa, Bangladesh, Indonesia and Russia are all attending
Observers have been closely watching China - the world's top emitter - for any commitments it might make at the meeting
In her remarks today, Greta Thunberg has once again challenged world leaders to do more to address the climate crisis.
"Unlike you, my generation will not give up without a fight," she says. "How long do you honestly believe that people in power will get away with it?"
Greta Thunberg warns US lawmakers over climate change
Image source, HouseThe Democratic congresswoman who has been a leader in the US climate fight is now speaking at the House Environment Subcommittee's hearing.
Alexandra Ocasio-Cortez of New York says Republicans continue to engage in myths about climate change as "a socialist conspiracy takeover".
"They fail to acknowledge what's happening right now," she says.
Fondly known as "AOC", the young lawmaker calls on witness Tara Houska, a Native American woman, to explain the disproportionate impacts of the climate crisis on communities like hers.
Houska says: "We are the people that are desperately experiencing the impacts of not just the climate crisis, but in the actual building of infrastructure."
Earlier this week, Ocasio-Cortez re-introduced her signature climate legislation, known as the Green New Deal, an ambitious framework for addressing climate change and speeding up the transition to renewable energy.
Patricia Espinosa, the executive secretary of the UN Framework Convention on Climate Change, the international treaty to address climate change, said the global climate emergency was “a clear, present and growing danger to all people on this planet.”
She observed that the leaders taking part in the summit represented nations that were responsible for 80% of global emissions, and their messages offered a “step in the right direction”.
Ms Espinosa added: “We congratulate the commitments shown by several nations at the summit and I urge all nations to carry forth this leadership and momentum to the crucial COP26 negotiations…in Glasgow.”
Image source, HouseSpeaking alongside Greta Thunberg as a witness at today's US House of Representatives subcommittee hearing is a woman billed as a "fracking refugee".
Jill Antares Hunkler was a seventh-generation resident of the Ohio Valley but was forced to move out because of a heavily polluting compressor station downwind of her home.
She describes her family and neighbours experiencing all kinds of symptoms from nausea and headaches to rashes and sleeplessness.
Hunkler says continuing to subsidise the fossil fuel industry worsens public health and plastic pollution, and hurts efforts to achieve environmental justice.
Image source, HouseGreta Thunberg tells lawmakers that "we are not treating this crisis like a crisis".
It creates "a hamster wheel" of people who do not adequately demand climate action voting in politicians who do little, she says.
"Someone needs to break that and the people with the most responsibility have the biggest opportunity to do that," testifies Thunberg.
Anthony Zurcher
BBC North America reporter
Joe Biden, in his morning address to the climate summit, pledged to cut US carbon emissions 50% below 2005 levels by 2030. It’s an ambitious goal and, even if he wins re-election in 2024, one that he won’t be in office long enough to see arrive.
Addressing climate change is all about setting long-term objectives, however, and given the constantly shifting US political environment, sticking to a consistent long-term policy is tricky.
Barack Obama signed the Paris Climate Accord. Donald Trump pulled the US out. Biden has rejoined it.
Obama promulgated environmental regulations, which Trump tried to rescind and Biden hopes to reinstate.
It’s enough to make liberal activists who listen to Biden’s words a bit jaded.
Making substantive progress on an environmental agenda – one that can’t be rolled back by a conservative president in 2024 or 2028 – requires laws passed by Congress. That’s why Biden’s proposed infrastructure legislation, with its massive investment in climate-oriented projects, is pivotal to his success on this issue – and why Biden specifically touted its benefits, both for the environment and the economy, in his opening remarks on Thursday.
The bill is currently being negotiated in Congress, and its passage is very much an open question. But it may be the best, if not the only, way Biden can ensure that the US makes substantive progress toward his announced emission targets.
John Kerry now introduces a panel of public and private sector groups that will discuss how to best invest in climate solutions.
He opens by posing the question: "How can public and private finance meet this challenge?"
He first calls upon Kristalina Georgieva, the Managing Director of the International Monetary Fund to speak.
"At the IMF we see climate change as central to our work," she begins.
Matt McGrath
Environment correspondent
After the first major session of the leaders climate summit a few things are clear.
Numerous technical glitches showed that negotiating via technology is really, really hard.
On the positive side, the US confirmed that it is right back in the mix and with some credibility as it put forward a pledge for 2030 that’s slightly bolder than many expected. It’s also significantly upped its financial commitments on climate.
Japan, South Korea and Canada put new targets on the table, although campaigners viewed the Canadian contribution as a bit limp.
Brazil’s President Bolsonaro softened his tone and promised an end to illegal deforestation.
Even President Putin showed up and made some soothing sounds about the need for international co-operation.
On the negative side, China and India took part but didn’t offer anything new – although China hinted that the days of coal are numbered.
For many contributors, the underlying message was that more action is certainly possible, but money is needed to make it happen.
Australia adopted a rather bullish tone, refusing to give a date when it might hit net zero.
Much of this was as expected, and it would be foolish to think the complex issue of climate change could be solved in a few hours via dodgy internet connections.
But it does show that there is significant heavy lifting required by the UK as president of COP26 before world leaders and their negotiators assemble in Glasgow in November.
Image source, pool"Like all island nations, we remain committed to climate action," says Prime Minister Andrew Holness of Jamaica.
"Major emitters should contribute more financially to the problem."
The women speaking so far at this summit are few and far between - as most of the heads of state who have spoken are men.
But next up is Prime Minister Jacinda Ardern of New Zealand.
"Both our financial systems and financial flows to assist developing countries is at the heart of that transition," she says.
She urges other nations to do what New Zealand has done and price carbon, end fossil fuel subsidies, and finance adaptation.
Image source, poolGreta Thunberg tells the committee's highest ranking Republican member, Ralph Norman, that there is "no magic number" of emissions reductions that is ideal.
Getting to as low a number or proportion of emissions as possible quickly should be the goal, she says.
She also adds that the large developed countries must take the lead in the climate fight.
This can create pressure on China and other countries that are not complying with global climate commitments, says Thunberg.
"If the US for example, which is the biggest emitter in history won't take action, then how can we expect other countries to do that?"
Image source, House of RepresentativesHouse Environment Subcommittee Chairman Ro Khanna, a Democrat from California, says the repeal of fossil fuel subsidies should be in President Biden's next big proposal - an infrastructure overhaul.
Thunberg agrees the repeal is much needed based on "the overall current best available science" but makes sure to point out "you don't need me saying this".
Biden's current infrastructure reforms do not include a subsidy repeal.
The US is currently the largest oil and gas producer in the world.
Under former president Donald Trump, the fossil fuel industry reportedly received between $10.4 (£7.5 bn) and $15.2 bn (£10.9 bn) in pandemic relief.
Thunberg notes repealing subsidies would amount to "bold action on reducing emissions at the source".
Reality Check
You can’t see or smell carbon dioxide (CO2) but it’s actually all around us and is at the heart of the world's changing climate.
Scientists believe the last time levels of CO2 in the atmosphere were as high as they are now was probably more than three million years ago.
Reality Check’s Chris Morris explains why limiting the amount of carbon dioxide we use is so important.
Climate Basics: CO2 explained
This next session will feature a few more world leaders - including Prime Minister Jacinda Ardern of New Zealand and President Félix Tshisekedi of the Democratic Republic of the Congo.
It will then move on to speakers from various organisations working to combat climate change including the International Monetary Fund, the World Bank, Allianz, and more.
Thunberg's opening statement is yet another sharp and pointed critique of leaders for being slow to adapt to the climate fight.
Climate activists are not naive, she says, and do not really expect countries and companies to take bold action.
Thunberg says the proof is that they are still "making vague, distant insufficient targets without any real pressure from the media and the general public".
"The general level of awareness is so absurdly low you still get away with not stopping fossil fuel subsidies," she points out, referring back to the topic of the hearing.
But "my generation will not give up without a fight", she warns, adding that leaders in the US and around the world will not continue to get away with their lack of urgency.
"We the young people are the ones who are going to write about you in the history books. We are the ones who get to decide how you will be remembered," she says.
"So choose wisely."
Climate activists have appeared to dump cow manure in front of the White House to protest about Biden's climate plan, which they say doesn't do enough.
It's unclear if they are protesting about his recent announcement of cutting greenhouse gases 50% by 2030, or if the protest was planned prior.
The Earth Day protest has a few dozen attendees and calls on Biden to declare a climate emergency.
It comes as Biden is hosting a climate summit with world leaders.
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Biden opens the second session with a short statement on the importance of reaching net zero emissions.
Special Presidential Envoy for Climate John Kerry is speaking now.
Image source, House of RepresentativesClimate activist Greta Thunberg is now giving her opening statement as a witness at the House of Representatives.
"I don’t represent any financial or political interest. I am not a lobbyist. So I can’t negotiate, compromise or make deals," she begins.
"All I can do is to urge you to listen to and act on the science, and to use your common sense."
Thunberg suggests the hearing is meaningless, by saying she will not bother explaining why fossil fuel subsidies are bad.
"It is proof that we have not understood the climate emergency at all," she says.
She calls on subsidies to be ended immediately.
The morning session is over and the summit will resume shortly.
Image source, PoolTeenage activist Xiye Bastida follows the world leaders as one of the summit's first invited speakers.
"I am one of the many young people impacted by climate change," she tells the summit, after an introduction from US Secretary of State Antony Blinken.
Her hometown in Mexico was hit by flooding in 2015 which led her family to move to New York.
"We can no longer keep having summits and conversations," she says to the summit.
She urges action and shares a list of demands.
"We demand comprehensive non-Eurocentric climate education," she says.
"We demand to get to net zero emissions by 2030, not 2050."
Greta Thunberg has participated in many climate strikes in cities around the world.
But perhaps most memorable was her impassioned speech at the UN Climate Action Summit in 2019, calling out world leaders for doing too little.
"You have stolen my dreams and my childhood with your empty words," she said.
"We are in the beginning of a mass extinction, and all you can talk about is money and fairy tales of eternal economic growth," she continued.
"How dare you!"
Thunberg: 'If you choose to fail us we will never forgive you'