No part of the planet will be spared a climate crisis as oceans warm and glaciers and ice sheets melt, according to a report by United Nations scientists.

The Intergovernmental Panel on Climate Change (IPCC) warns one billion people will be affected as soon as 2050 because of rising sea levels, water shortages and food insecurity.

The report, compiled by more than 100 leading climate scientists, calls for urgent, ambitious and coordinated action.

In full: Climate activist Greta Thunberg calls out world leaders

Image: Sea levels are now rising by 3.6mm a year, more than twice the rate of the last century

The findings are corroborated by scientists in the Arctic, who showed Sky News evidence of "unprecedented" ice melt. One cautioned against buying coastal property.

Debra Roberts, one of the IPCC authors, urged world leaders to redouble efforts to reduce greenhouse gas emissions and keep the global temperature rise to below 2C, as agreed in Paris in 2015.


"The more decisively and the earlier we act, the more able we will be to address unavoidable changes, manage risks, improve our lives and achieve sustainability for ecosystems and people around the world - today and in the future," she said.

The report, The Ocean and Cryosphere in a Changing Climate, says the impact of warming air temperatures in polar regions is accelerating.

Arctic snow cover has shrunk by one million square miles since 1967. The extent of the sea ice at the end of the summer melt season was this year at its second lowest on record, with conditions "unprecedented for at least 1,000 years", the report says.

Between 2006 and 2015, 650 billion tonnes of ice a year were also lost from Greenland, Antarctica and the world's glaciers.

Sky News was taken to a glacier near Ny Alesund, a research base on the Norwegian archipelago of Svalbard, 800 miles from the North Pole.

Image: A glacier near Ny Alesund, a research base on the Norwegian archipelago of Svalbard, 800 miles from the North Pole

Image: Arctic snow cover has shrunk by one million square miles since 1967

Measuring poles in the ice showed that the glacier had thinned by more than two metres since the spring. The ice won't be replaced over winter because of reduced snowfall.

Jack Kohler, of the Norwegian Polar Institute, said: "This is unprecedented. It is increasing sea level and that will continue and accelerate in future.

"What happens in the Arctic doesn't stay in the Arctic.

"Don't buy oceanfront property."

The IPCC scientists have dramatically raised their projections for future sea level rise as evidence grows that the Antarctic ice sheet is becoming unstable and vulnerable to breaking up.

Sea levels are now rising by 3.6mm a year, more than twice the rate of the last century.

But if greenhouse gas emissions continue at their current rate, sea level rise will accelerate to several centimetres a year in the 22nd century and several metres a year in the 23rd century.

Image: Greta Thunberg (3rd L), with Intergovernmental Panel on Climate Change (IPCC) vice-chairman Youba Sokona (4th R) and IPCC working group II co-chairman Debra Roberts (3rd R)

Image: Once in a century floods may happen once a year by 2100

"Once-in-a-century" floods and storm surges are expected to happen at least once a year in many parts of the world by 2100.

Dr Helene Hewitt, head of ocean modelling at the UK's Met Office, said: "Today's report makes a very strong link between future rises in sea levels and increased coastal flood risk with extreme sea level events that are historically rare becoming more common by 2100.

"Around the UK coasts, UKCP climate projections show that sea levels will continue to rise, with a possible increase in London of 115cm under the worst-case greenhouse gas emission scenario by 2100."

Glaciers in high mountain areas will also shrink, with some in the Alps disappearing altogether.

In areas such as the Himalayas millions of people depend on a steady flow of glacier meltwater for drinking, cooking and irrigation.

The report also warns of dramatic impacts on the ocean, which has absorbed 90% of the heat from global warming.

Marine heatwaves are expected to become 50 times more common by the end of this century compared to 1850-1900. Most coral reefs, which are highly temperature sensitive, will die.

Rising water temperature is also depleting oxygen levels, and the oceans are also becoming more acidic as they absorb more carbon dioxide.

The effect is to make the oceans more hostile to life, with fish stocks likely to fall.

Dr Stephen Cornelius, WWF chief adviser on climate change, said: "We cannot gamble with people's lives.

"Given the stakes, leaders must act now to ensure a positive future for the planet and invest in rapid and deep cuts to greenhouse gas emissions as well as significantly increasing funding for resilience and adaptation."