Mark Lowen
BBC Italy Correspondent in Rome

Prince Charles's mere presence here speaks volumes - it is rare for a member of the royal family to be invited to one of these G20 summits - the meeting of the world's largest economies.

These countries produce 80% of global greenhouse gas emissions so Prince Charles addressed the summit in recognition of the need to mobilise all forces - political and royal in this case - to try to corral world leaders to stick to their pledges of a 1.5C on global warming and net zero carbon emissions.

He urged world leaders to form public-private partnerships to transition to greener cleaner energy.

He said this was the defining challenge of our times and that nature was at stake. It was a very heartfelt address from a man who has been a lifelong environmentalist.

Prince Charles has told the leaders of the world's largest economies, and largest emitters, that they have "an overwhelming responsibility to generations unborn", calling COP26 in Glasgow "the last chance saloon".

Speaking at the G20 summit in Rome, he called on governments to work with the private sector to try to create the investment in green infrastructure, energy and new jobs needed to meet the 1.5C target, which scientists say is quickly moving out of reach.

To remind you, Boris Johnson and other world leaders are at this other summit in Rome this weekend. If they are able to agree a strong declaration there on climate change, that would be very positive for the climate change conference in Glasgow.

Image source, PA Media

We've had a flurry of interviews this morning as the COP summit gets going.

Among the big names talking is 18-year-old climate activist Greta Thunberg, who was mobbed by crowds yesterday as she arrived on a "climate train" from Amsterdam carrying delegates and youth activists.

Asked if she might stand for office, she told the BBC it was more effective to change narratives "from the streets" rather than from "the inside".

Defending the actions of protest groups such as Insulate Britain, she told Andrew Marr "sometimes you need to anger some people" to have an impact on public perception.

"We are activists because we are very positive that we can actually change [the course of events]."

She's just one of thousands of activists who will be taking to the streets of Glasgow during this summit.

Ed Miliband, the shadow business and energy secretary, has just been speaking to the BBC's Andrew Marr.

If we're to tackle "deeply worrying situation" of climate change and keep the target of 1.5C of warming alive, we need to halve global emissions this decade, he says.

But at the moment, the UN says we will only cut them by 7%, leaving a "huge gap".

"We've got to push really hard at this summit. This has to be a real negotiation, not people coming along with their pre-prepared statements."

The UK government must put "proper pressure" on the world's big emitters at COP26," Miliband says. "Australia's commitment will take us to a 4 degree world."

There should be no "free passes at this summit whether its China, Australia or anyone else".

COP26 - which opens in the next half an hour - is expected to see the biggest ever deployment of armed officers in Scotland.

Police Scotland has 500 officers trained to use guns and they will be joined by others from around the UK.

The force will not give an exact number for how many will be on duty during the conference, but one former chief constable has suggested it could be about 1,000.

Operation Urram (Gaelic for respect) will see a total of 10,000 officers deployed on each day of the two-week summit.

The Scottish Event Campus (SEC) venue will become United Nations territory, guarded by armed UN personnel.

They will be based around the five interconnected exhibition and event halls of the SEC Centre, plus the 3,000-seat Armadillo and 14,300-seat Hyrdo arenas.

Major demonstrations and protests are expected, but Police Scotland bosses are confident they will cope.

Chief Superintendent Louise Skelton said:"There is no specific threat to the event at the moment but we continue to monitor any intelligence that comes in, and link in with the security services."

Tina Stege, climate envoy for the Marshall Islands, says if global temperatures rise above 1.5C, it will be "unimaginable" for the 60,000 people who live in her country.

She says sea levels were already rising and "creating inundations" on a yearly basis in the chain of islands in the Pacific.

She describes COP26 as "a hugely important moment" and offers a warning to the world: "We are going to be hit earliest and hardest, but this crisis is going to affect us all."

Image source, Getty Images

Andrew Marr is asking COP26 president Alok Sharma if China can be persuaded to go further with its climate change commitments.

"It moved forward somewhat since 2015 but of course we expected more," he says.

But he calls COP26 a "real opportunity" for China to "step up and show further leadership."

He says the country has pledged to stop international coal financing and domestic coal will start to go down from 2026 but says "we need to see the detail".

It's worth noting that China, the world's largest emitter, recently boosted coal output due to a power crisis.

Sharma adds: "I want to see more commitment from all countries here but ultimately this will come down to what we are able to negotiate."

According to Climate Action Tracker, an international group of scientists and policy experts, China's current actions to meet its commitments are "highly insufficient".

Andrew Marr is repeatedly asking Alok Sharma if he thinks he can really get world leaders to agree to action that will limit average temperature rises 1.5C.

Sharma acknowledges it will be "very, very tough".

"We are heading towards two degrees but need to ensure we are heading lower than that," he says.

He says the 2.7C that the UN says the world is heading for doesn't take into account all of the net zero targets that countries have made.

Scientists say there simply isn’t time for inaction if 1.5C is to be achieved, while some believe we’ve already left it too late.

COP26 President Alok Sharma is talking to the BBC's Andrew Marr just before he heads off to officially open the climate change conference.

He says climate change is a "huge challenge that we face collectively".

"The world needs to come together and ensure that we are doing our bit to limit global temperature rises."

He says there has been progress since the 2015 COP summit Paris, when all the world's countries came together in an agreement pledging to tackle climate change and keep warming to below 2C and ideally 1.5C by 2100.

The UN recently said we were on track for 2.7C - but Sharma and UK PM Boris Johnson want to use this conference to "keep 1.5 alive".

We've got about an hour until the COP26 summit officially kicks off, so we’re going to go back to basics here on climate change for everyone who needs a refresher.

The climate is the average weather in a place over many years. And so climate change is a shift in those average conditions.

The rapid climate change we are seeing now is caused by humans using oil, gas and coal for their homes, factories and transport.

When these fossil fuels burn, they release greenhouse gases – mostly carbon dioxide(CO2). These gases trap the Sun’s heat and cause the planet’s temperature to rise.

The world is now about 1.1-1.2C warmer than it was in the 19th Century – and the amount of CO2 in the atmosphere has risen by 50%.

In order to avoid the worst consequences of climate change, scientists say temperature rises must slow down. They warn global warming needs to be kept to 1.5C by 2100.

Teenage activist Greta Thunberg, COP26 President Alok Sharma and Shadow Business and Energy Secretary Ed Miliband are among the guests talking to Andrew Marr on his Sunday show this morning. It's just started.

We'll be bringing you updates here and if you're in the UK you can also watch live by clicking the play button at the top of this page.

Image source, Getty Images

The COP26 conference is formally being opened this morning in Glasgow but many of the key players are in Rome for the G20 summit. The G20 is a global forum where 19 countries and the EU discuss major issues.

What happens there is really important for the climate summit because the G20 includes some of the world’s most polluting economies. In fact, the group is estimated to account for 80% of the world's emissions.

Lesser-developed countries, some of which are suffering from the worst effects of climate change, are relying on G20 nations to pledge more financial aid and come up with better targets on cutting their emissions.

There is a particular focus on China and India - the world’s 1st and 3rd largest emitters respectively on a country basis. They have not submitted more ambitious targets ahead of COP despite pressure from the US, and the conference’s hosts, the UK.

Can COP26 really save the planet?published at 08:21 Greenwich Mean Time 31 October 2021

08:21 GMT 31 October 2021

David Shukman
Science editor, BBC News

At face value, things do not look promising, for a simple reason: the previous 25 of these giant conferences failed to turn off the tap of the greenhouse gases that are driving up global temperatures.

Despite three decades of talking, the planet is now at least 1.1C hotter than the pre-industrial level - and rising.

For this conference, however, expectations for real progress are higher than usual.

That's partly because the risks are hitting home. This year floods killed 200 people in Germany, heatwaves struck chilly Canada and even the Siberian Arctic was burning.

And scientists are clearer than ever that avoiding the most damaging temperatures means halving global carbon emissions by 2030 - a deadline looming close enough to focus minds.

David Shukman has been reporting on climate change for nearly 20 years. This is his 10th COP summit.

Image source, Getty Images

Thousands of climate activists are descending on Glasgow for the summit - including perhaps the most famous of them all, Greta Thunberg.

The Swedish teenager was mobbed as she arrived on a "climate train" on Saturday evening.

The specially-chartered train, which arrived from Amsterdam, also had on board some 500 passengers including delegates from the Netherlands, Belgium, Italy and Germany, as well as 150 youth activists and members of the European Parliament.

Many participants and activists are taking the train to Glasgow as it is a more sustainable way to travel than flying.

You might remember that Greta herself once took a boat to New York to attend a UN climate summit because she didn't want to fly.

Image source, Getty Images

Image source, Getty Images

In a line: The COP26 summit from 31 October to 12 November brings the world together to discuss how we tackle climate change and could lead to major changes to people's everyday lives across the globe

Why it matters: Fossil fuel emissions caused by humans are causing global warming and we’re already seeing extreme weather events linked to climate change. Urgent action is needed to avoid catastrophic consequences to the planet

What to look out for: Nearly 200 countries are being asked for their updated plans to cut emissions by 2030. They have all already vowed to keep global warming "well below" 2C above pre-industrial levels - and to try aim aim for 1.5C. This conference will be about putting those promises into action, and some form of declaration is expected

What’s the reality: Some scientists say it’s already too late to achieve the 1.5C target, which is expected to be breached between 2030 and 2040. Ahead of the conference, the UN said that we were headed for 2.7C despite all the pledges already made.

Go deeper: What is the climate conference in Glasgow all about?

After years of preparations, it’s here - the international climate change conference in Glasgow, Scotland, that has been billed by some as the “last best chance” we have to avert the worst consequences of climate change.

Later this morning, after a year’s delay due to the Covid pandemic, COP26 will formally be opened. And from now until 12 November, up to 25,000 people including world leaders, delegates, campaigners and journalists are expected to attend.

And a “conference” might sound boring but this one could eventually lead to major changes to our everyday lives. The kind of car we drive, how we power and heat our homes and how we live in the future are all going to be discussed. Of course, there's no guarantee that world leaders will agree on the action that needs to be taken.

Over the next two weeks we’ll bring you live coverage of the key issues being debated and put the announcements into context and explain what they mean to all of us. You’ll also hear from people living on climate frontlines around the world. Stay with us.