Chris Morris
BBC Reality Check

We’re going to hear a lot today about pledges for reducing carbon emissions, and many of the numbers will sound impressive.

But we’re still waiting for a lot of the detailed policy about how change will be implemented.

Much of the progress made so far in reducing emissions has been achieved by removing coal, the most polluting of fossil fuels, from energy networks.

But harder tasks lie ahead. We’ve looked into how well UK governments have met previous climate targets here.

Roger Harrabin
BBC environment analyst

Image source, Reuters

The oceans are in distress, according to a UN report, external released today.

It warns the seas are suffering from overfishing, pollution and aquaculture.

And it says that if we don’t protect the oceans we will be fuelling climate change anyway, because the seas help to regulate global temperatures by taking up CO2 and producing oxygen.

The new documentary film Seaspiracy on Netflix has been criticised by some for exaggeration, but it highlights how fishing is disrupting the food chain by taking out top predators.

It also points to the vast amounts of plastic fishing gear discarded or lost a far greater threat than plastic straws.

The UN’s report says:

• Rising carbon dioxide emissions have led to ocean acidification
• The number of “dead zones”, or areas with reduced oxygen in the ocean, has increased from more than 400 globally in 2008 to about 700 in 2019.
• Around 90% of mangrove, seagrass, and marsh plant species - as well as 31 percent of species of seabirds - are threatened with extinction.
• Approximately 15% of all sandy beaches worldwide are seeing retreating shorelines at an average trend of 1 metre/year or more over the last 33 years.

Image source, Getty Images

The world’s most famous climate activist will testify on Thursday to a committee of the House of Representatives, which is the lower chamber of the US Congress.

The 18-year-old will feature at a specially convened meeting of the House Oversight Subcommittee on the Environment, about the role of fossil fuel subsidies in preventing action, starting at 1500 BST (1000 local).

When she addressed Congress in 2019, her exchange with a Republican congressman made headlines. You can watch it below.

https://www.bbc.co.uk/news/av/world-us-canada-49748345

At 1300 BST (0800 local), President Biden and Vice-President Kamala Harris will open the first session of the two-day summit, in which leaders from dozens of countries will talk about the challenges their nations face, and what new steps they are taking to address climate change.

Among those invited are:

• Chinese President Xi Jinping
• Russian President Vladimir Putin
• German Chancellor Angela Merkel
• UK Prime Minister Boris Johnson
• UN Secretary General Antonio Guterres
• Australian Prime Minister Scott Morrison
• Brazilian President Jair Bolsonaro
• South African President Cyril Ramaphosa

The second session at 1645 BST (1145 local) will look at ways to increase the financing of solutions especially in developing countries, and will feature US Treasury Secretary, US climate envoy John Kerry, Pope Francis and New Zealand Prime Minister Jacinda Ardern.

Another group at 1745 BST (1245 local) will look at ways to increase resilience to the impacts of climate. And at 1900 BST (1400 local) defence ministers from assorted countries will discuss the global security implications.

Day Two will focus on tech solutions and the economic opportunities in taking action, and will include Bill Gates among the speakers.

Image source, Getty Images

The UK has been keen to display its ambition on tackling the climate crisis ahead of the US Leaders Summit.

Earlier this week, the UK pledged a 78% cut in its emissions by 2035 compared with 1990 levels.

And it is also hosting the crucial COP 26 climate summit in Glasgow later this year.

According to the news agency PA, Prime Minister Boris Johnson is expected to tell the meeting in Washington that 2021 must be the year countries "get serious" about tackling climate change.

He will say: "The UK has shown that it's possible to slash emissions while growing the economy, which makes the question of reaching net zero not so much technical as political.

"If we actually want to stop climate change, then this must be the year in which we get serious about doing so.

"Because the 2020s will be remembered either as the decade in which world leaders united to turn the tide, or as a failure."

He will urge leaders to come to Glasgow in November - and Kunming in China in October for a summit on tackling declines in nature - armed with ambitious targets and the plans required to reach them.

He will add: "Let the history books show that it was this generation of leaders that possessed the will to preserve our planet for generations to come."

Matt McGrath
Environment correspondent

The Trump years marked a new low in US relations with the global community on the issue of climate change.

One of President Biden's first acts on the day of his inauguration was to rejoin the Paris climate agreement, which his predecessor had castigated as "unfair" when he announced the US would leave the pact in 2017.

But the perception that the US has been an unreliable partner on climate change does not just rest with Donald Trump.

Former UN climate chief Yvo de Boer, who ran global climate talks between 2006-2010, had this scathing assessment of America's previous record on the climate.

“I’ve still got the photograph on my desk of Al Gore signing the Kyoto Protocol in the full knowledge that he was never going to take it to the Senate,” he told the BBC, referring to an earlier global climate treaty, agreed in 1997.

“Then Obama signed the Paris Agreement, and Trump walked away. And now Biden's back and he thinks he can convene the whole world because he's the champion of climate action.”

There are obviously some bridges to be mended - that's one of the key reasons the Biden leaders summit is taking place.

David Shukman
Science editor, BBC News

The UK’s pledge to cut its carbon emissions by 78% by 2035 is likely to cause a bit of a stir at President Biden’s climate summit – it’s an eye-catchingly large number.

But the more ambitious a target, the greater the scrutiny about whether the government is doing the right things to deliver it.

The question I keep hearing from experts in the field is “where’s the plan?” - meaning the policies on everything from heat pumps to hydrogen, charging points to loft insulation.

Strategy documents are promised in the coming months and they should spell out the answers but most have been delayed.

Perhaps the most important is one by the Treasury which will set out the financial arrangements – basically, answering the crucial question of who pays?

Ministers reject the suggestion that they don’t have a strategy but the criticism is likely to continue until their ambition is underpinned by hard detail.

Welcome to our coverage of the Leaders Summit on Climate, to be held virtually from the US.

The US wants to re-assert its global leadership on climate change after President Trump pulled the country out of the Paris climate agreement.

Some 40 world leaders are expected to attend the key meeting, including President Xi Jinping of China and UK Prime Minister Boris Johnson.

The UK is hosting another climate meeting at the end of the year, known as COP 26, which is seen as crucial for keeping the planet's temperature rise under 1.5C.

At Thursday's meeting in the White House, it is expected that America will unveil an updated carbon pledge that will see its emissions nearly halved by 2030.

We'll bring you all the news updates, debate and analysis as the day unfolds.

Image source, Getty Images