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NASA sees unavoidable sea level rise ahead

AFP logoAFP 26/08/2015 Axel Heimken
According to NASA's sea level rise team, it's pretty certain we are locked into at least three feet (one meter) of sea level rise, and probably more, however it is not clear when this will occur © AFP PHOTO According to NASA's sea level rise team, it's pretty certain we are locked into at least three feet (one meter) of sea level rise, and probably more, however it is not clear when this will occur

The latest data on sea level rise from global warming suggests that three feet (one metre) or more is unavoidable in the next 100-200 years, NASA scientists said Wednesday.

Much uncertainty remains in the predictions - particularly with regard to timing - because scientists do not know how fast major polar ice sheets will melt.

But a wealth of data in the past few years from satellite instruments shows that oceans are swelling much faster than they have in years' past.

"Given what we know now about how the ocean expands as it warms and how ice sheets and glaciers are adding water to the seas, it's pretty certain we are locked into at least three feet (one metre) of sea level rise, and probably more," said Steve Nerem of the University of Colorado, Boulder and leader of NASA's sea level rise team.

"But we don't know whether it will happen within a century or somewhat longer."

The last major predictions were made in 2013 by the United Nations Intergovernmental Panel on Climate Change (IPCC).

Based on a consensus of international researchers, the IPCC said global sea levels would likely rise from one to three feet by the end of the century.

Nerem said new satellite data suggests the higher end of that range is more likely.

Scientists are particularly focused on the Greenland ice sheet, which shed an average of 303 gigatons of ice a year over the past decade.

Also, the Antarctic ice sheet has lost an average of 118 gigatons a year.

But scientists have never seen an ice sheet collapse, so the question of when sea levels will rise drastically is a major mystery.

The world's oceans have risen an average of almost three inches (7.6 cm) since 1992, with some locations rising more than nine inches (23 cm) due to natural variation, NASA said.

"We've seen from the paleoclimate record that sea level rise of as much as 10 feet (three metres) in a century or two is possible, if the ice sheets fall apart rapidly," said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington.

"We're seeing evidence that the ice sheets are waking up, but we need to understand them better before we can say we're in a new era of rapid ice loss."

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