Half of Greenland and vast areas of Antarctica are destined to melt if global warming continues at the same pace until the end of the century, scientists warned on Thursday.
Their research shows that the loss of so much ice will trigger dramatic rises in sea levels, ultimately swamping low-lying islands and coastal regions and threatening the flood defenses of cities such as London.
The last time so much ice was lost from the poles -- in a period between ice ages 129,000 years ago -- global sea levels rose between 4m and 6m.
Experts believe many coastal regions would suffer long before sea levels rose significantly, because even a minor rise will make storm surges more devastating and increase the risk of flooding.
The warning comes from climate scientists who combined historical records of Arctic and Antarctic ice melting with advanced computer models capable of predicting future environmental conditions.
They found that if nothing is done to put the brakes on climate change, Greenland, the west Antarctic ice sheet and other expanses of polar ice will be warmed beyond a "tipping point" after which their melting is inevitable.
Jonathan Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona, and Bette Otto-Bliesner, at the US National Center for Atmospheric Research in Colorado, looked back in history to find a time when sea levels were higher than they are today.
They identified a period when glacial melting increased sea levels by several meters.
They used a computer model of the environment to work out how warm the world must have been to trigger the mass melting and concluded that the Earth was between 3oC and 5oC warmer than it is today.
Using the same model, the scientists spun the clock forward to see when climate change is likely to make the world as warm again.
"We showed that that level of warming will come later in this century unless we act on carbon emissions," Overpeck said.
"An Arctic warming of 3oC to 5oC is enough to cause 4m to 6m of sea level rise," he said.
If temperatures do rise as the scientists predict, the ice at the poles will not be lost immediately. Enough ice is likely to melt within the next 100 years to raise sea levels by a meter, but ultimately the fresh water pouring into the North Atlantic would slow down the Gulf stream by a quarter.
"These ice sheets have melted before and sea levels rose. The warmth needed isn't that much above present conditions," said Otto-Bliesner.
The major concern is that unless climate change slows down significantly, the eventual loss of polar ice and subsequent 6m rise in sea levels will become unavoidable.
"There has been an increasing number of observations from the ice sheets suggesting they are responding faster to climate change than anticipated," Overpeck said.
"Now along come our results showing these kinds of changes occurred in the past and lead to large ice sheet retreat and sea level rise," he said.
A 1m rise in the sea level would see the Maldives disappear, make most of Bangladesh uninhabitable and put cities such as New Orleans "out of business," according to Overpeck.
The research was published in two papers in the US journal Science on Thursday.
Super Typhoon Kong-rey is the largest cyclone to impact Taiwan in 27 years, the Central Weather Administration (CWA) said today. Kong-rey’s radius of maximum wind (RMW) — the distance between the center of a cyclone and its band of strongest winds — has expanded to 320km, CWA forecaster Chang Chun-yao (張竣堯) said. The last time a typhoon of comparable strength with an RMW larger than 300km made landfall in Taiwan was Typhoon Herb in 1996, he said. Herb made landfall between Keelung and Suao (蘇澳) in Yilan County with an RMW of 350km, Chang said. The weather station in Alishan (阿里山) recorded 1.09m of
STORM’S PATH: Kong-Rey could be the first typhoon to make landfall in Taiwan in November since Gilda in 1967. Taitung-Green Island ferry services have been halted Tropical Storm Kong-rey is forecast to strengthen into a typhoon early today and could make landfall in Taitung County between late Thursday and early Friday, the Central Weather Administration (CWA) said yesterday. As of 2pm yesterday, Kong-Rey was 1,030km east-southeast of Oluanpi (鵝鑾鼻), the nation’s southernmost point, and was moving west at 7kph. The tropical storm was packing maximum sustained winds of 101kph, with gusts of up to 126 kph, CWA data showed. After landing in Taitung, the eye of the storm is forecast to move into the Taiwan Strait through central Taiwan on Friday morning, the agency said. With the storm moving
NO WORK, CLASS: President William Lai urged people in the eastern, southern and northern parts of the country to be on alert, with Typhoon Kong-rey approaching Typhoon Kong-rey is expected to make landfall on Taiwan’s east coast today, with work and classes canceled nationwide. Packing gusts of nearly 300kph, the storm yesterday intensified into a typhoon and was expected to gain even more strength before hitting Taitung County, the US Navy’s Joint Typhoon Warning Center said. The storm is forecast to cross Taiwan’s south, enter the Taiwan Strait and head toward China, the Central Weather Administration (CWA) said. The CWA labeled the storm a “strong typhoon,” the most powerful on its scale. Up to 1.2m of rainfall was expected in mountainous areas of eastern Taiwan and destructive winds are likely
The Central Weather Administration (CWA) yesterday at 5:30pm issued a sea warning for Typhoon Kong-rey as the storm drew closer to the east coast. As of 8pm yesterday, the storm was 670km southeast of Oluanpi (鵝鑾鼻) and traveling northwest at 12kph to 16kph. It was packing maximum sustained winds of 162kph and gusts of up to 198kph, the CWA said. A land warning might be issued this morning for the storm, which is expected to have the strongest impact on Taiwan from tonight to early Friday morning, the agency said. Orchid Island (Lanyu, 蘭嶼) and Green Island (綠島) canceled classes and work
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