Ice scientists are alarmed after the “doomsday” glacier, which is around the size of the Great Britain, is melting faster than 30 years ago and showing cracks.
Thwaites, a West Antarctic ice sheet in the Antarctic peninsula, could cause a half-metre rise in global sea levels, experts have warned.
The threat comes after researchers also discovered big fissures on top and underneath the West Antarctic ice sheet, prompting fears that it could collapse in less than five years.
Thwaites already contributes to four per cent of worldwide global sea level rises, and satellite studies show its melting is happening faster than in the 1990s.
The glacier is blocking many other huge glaciers in Antarctica which are also deteriorating as the Southern Ocean warms, and scientists think that if Thwaites collapses, so will the whole ice sheet, causing several metres of sea level rises.
Currently, sea levels are rising fast, and even a part of Thwaites disappearing could increase the severity of storm surges, according to The Guardian.
If all of West Antarctica’s glaciers ever collapse, all coastal cities in the world would be flooded, leading to the loss of lives, livelihoods and hard-hit economies, according to the newspaper.
Although scientists believe massive glaciers such as Thwaites shouldn’t collapse until after centuries of global heating, the loss of sea ice in the Arctic and of Larsen B 20 years ago raised concerns that a much quicker disaster could unfold.
Larsen B, which was believed to weigh around 500 billion tonnes and be 3,250-sq-km in length, surprised everyone when it broke off the Antarctic continent and into thousands of icebergs in only one month.
Earlier this year, the United Nations warned humans’ harmful impact on the planet is already “locked in” for decades but the climate crisis could get much worse.
The UN Intergovernmental Panel on Climate Change (IPCC) warned in a report that without rapid and large-scale action to cut down emissions, global temperatures are set to increase – and pass the critical 1.5-degree Celsius threshold in the next two decades.
UN Secretary General Antonio Guterres said the report is a “code red for humanity”.
He added: “The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk.
“Global heating is affecting every region on Earth, with many of the changes becoming irreversible .
“This report must sound a death knell for coal and fossil fuels, before they destroy our planet.”
In recent months, environmental problems included wildfires in Turkey, Greece, Cyprus, Russia and Italy.
There have also been floods across European countries which caused people to die in Germany, Belgium, Romania, Austria and Italy.
Guterres called for government leaders and all stakeholders to come together to avoid a “climate catastrophe” – and stressed there is “no time for delay and no room for excuses”.
Related: EU move to ban products linked to deforestation two weeks after Cop26