Greta Thunberg is running late to the COP 25 climate meeting in Madrid, Spain, after hitching a ride with an Australian couple travelling the world by boat so she would make it on time.

Key points: Ms Thunberg estimated she'd arrive on Tuesday morning local time

Ms Thunberg estimated she'd arrive on Tuesday morning local time The meeting was moved from Chile to Spain after unrest in the South American country

The meeting was moved from Chile to Spain after unrest in the South American country The summit aims to put the finishing touches to the rules governing the 2015 Paris accord

Ms Thunberg broke the news of her late arrival to the conference of the parties on Monday: "We're speeding towards Europe!

"Estimated time of arrival right now is Tuesday morning [local time]. We'll be arriving at Doca de Alcantara, Lisbon. We are all looking forward to see you there!"

The first day of the conference, slated to run until December 13, saw UN secretary-general Antonio Guterres declare "the point of no return is no longer over the horizon".

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Mr Guterres warned: "In the crucial 12 months ahead, it is essential that we secure more ambitious national commitments — particularly from the main emitters — to immediately start reducing greenhouse gas emissions at a pace consistent to reaching carbon neutrality by 2050.

"We simply have to stop digging and drilling and take advantage of the vast possibilities offered by renewable energy and nature-based solutions."

The summit, which moved to the Spanish capital Madrid after Chile had to pull out amid anti-government protests, aims to put the finishing touches to the rules governing the 2015 Paris accord.

That involves creating a functioning international emissions-trading system and compensating poor countries for losses they suffer from rising sea levels and other consequences of climate change.

The annual Conference of the Parties is usually an important assessment of where the world stands on climate change.

For the past 25 years, negotiators from almost 200 countries have gathered to try to advance a global strategy for tackling rising temperatures.

Countries agreed in Paris four years ago to limit global warming to well below 2C, ideally 1.5C, by the end of the century compared with pre-industrial times.

Already, average temperatures have increased by about 1C, leaving little room for the more ambitious target to be met.

Ms Thunberg had travelled from Sweden to California by boat, train and electric car and was on track to attend the next round of climate negotiations in Santiago until the meetings were moved to Madrid and she was forced to find a way to get to Europe.

The country had backed out of hosting the COP 25 due to weeks of anti-government protests.

The 16-year-old tweeted from Los Angeles at the time: "As #COP25 has officially been moved from Santiago to Madrid I'll need some help."

"It turns out I've travelled half around the world, the wrong way. Now I need to find a way to cross the Atlantic in November … If anyone could help me find transport I would be so grateful."

Days later, Ms Thunberg posted to her Instagram again saying she had accepted the offer of couple Riley Whitelum and Elayna Carausu and their son Lenny to make the trip to Europe on their 48-foot catamaran called La Vagabonde.

The teen climate activist refuses to fly because of the carbon emissions involved.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 44 seconds 44 s Mr Guterres warned that humanity was running out of time to save itself from climate change.

Oxfam report shows 'climate chaos'

The latest Oxfam report, released in conjunction with the climate summit, has found people were three times more likely to be displaced by cyclones, floods or fires than by conflicts.

Some countries had been battered by both droughts and floods and sometimes in the same year, the report found.

Fiercer weather and worsening wildfires drove more than 20 million people from their homes over the past decade — a problem set to worsen unless leaders act swiftly to head off surging climate threats, Oxfam found.

Much of the displacement caused by cyclones, floods and fires appeared temporary and in some cases due to better efforts to evacuate people ahead of danger.

Environmental stress can hamper women's ability to adapt in climate change hotspots, like Bangladesh. ( Getty Images: Zakir Hossain Chowdhury/Barcroft Media )

But its "sheer scale" was a surprise, Oxfam's climate policy leader, Tim Gore said.

Nations such as Cuba, Dominica and Tuvalu are seeing on average close to 5 per cent of their people out of their homes in any given year, he added.

"This is the warming world we have long been warning about. Now we're seeing it play out before our eyes."

The Oxfam study examined the numbers of people displaced inside their home countries by climate-fuelled disasters between 2008 and 2018, based on Government and international agency data, as well as media reports.

Confluence of disasters leaves many poor nations — where most of the displacement is occurring — struggling to recover from one crisis before the next hits, Mr Gore said.

"This is climate chaos — what it actually looks like," he said.

Seven of the top 10 countries with the highest displacement by proportion of their population were developing island states, largely in the Pacific and the Caribbean, the report found.

But around 80 per cent of all people forced from their homes by weather disasters over the past decade were in Asia, where large populations in countries from the Philippines to Sri Lanka live in areas threatened by cyclones or flooding.

ABC/AP