Ice Sheet Melting Triples In 20 Years

The planet's two largest ice sheets are melting three times faster today than they were in the 1990s, according to a new study.

The most accurate analysis of satellite measurements to date showed that the Antarctic and Greenland ice sheets have lost four trillion tons of ice since 1992.

The melt water has added 11.1mm to global sea levels.

But the scientists warned that the rate of ice loss is accelerating. Figures published in the journal Science show that melting ice now adds 0.95mm a year to sea levels, compared to 0.27mm in the 1990s.

Study leader Professor Andrew Shepherd told Sky News: "This is hugely significant. Ice loss has tripled in 20 years. What will happen in the next 20, 40, 60 years?"

Even small sea level changes are a substantial threat to low-lying areas, particularly during storm surges.

"Low-lying areas need to consider infrastructure now," said Professor Shepherd.

"London will have to build a new flood barrier in the next century. It would take 30 years to build, so planning needs to start soon."

Much of the rise in sea levels is due to thermal expansion from warmer water. But melting ice sheets now contribute 30% to the overall rise, compared to just 10% in the 1990s.

Until now there has been uncertainty over how a warmer world was affecting the ice on the Greenland and Antarctic land masses.

Some studies have suggested the amount of ice has increased; others have indicated substantial losses.

But the new research used data from 10 different satellite missions to precisely measure the thickness of the ice sheets.

The observations should lead to more accurate predictions of the effects of climate change.

Professor Richard Alley, a climate scientist at Penn State University in the US, said: "This project is a spectacular achievement.

"The data ... will lead to a better understanding of how sea level change may depend on the human decisions that influence global temperatures."