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Dramatic sea-level rise imminent, new study shows

Image: NASA

Image: NASA

Daniel Martins
Digital Reporter

Monday, July 13, 2015, 12:46 GMT - In a warming world, we know ocean levels are likely to rise, but just how much?

There've been a lot of estimates cited in recent years, based on how rising temperatures are expected to interact with Earth's current ice caps, but new research published last week attempts to predict the future by looking at the past.

And it doesn't look good. According to scientists at the University of Florida, the last time global temperatures were this high, the sea levels rose as much as six metres.

"While this amount of sea-level rise will not happen overnight, it is sobering to realise how sensitive the polar ice sheets are to temperatures that we are on path to reach within decades," lead researcher Andrea Dutton said in a release from the university.

Greenland Ice Sheet (3970865344).jpg
"Greenland Ice Sheet (3970865344)" by Christine Zenino from Chicago, US - Greenland Ice Sheet Uploaded by russavia. Licensed under CC BY 2.0 via Wikimedia Commons.

The researchers say the last time sea levels were more than six metres higher than today was around 125,000 years ago, when global temperatures were 1oC higher than pre-industrial levels, or more or less close to today's level. They were at that level also around 400,000 years ago, when global temperatures were as much as 2oC higher than the preindustrial average.

Our own prognosis looks even worse when you look at carbon levels. The researchers say carbon levels during previous eras of higher sea levels peaked at 280 parts per million. Today's levels are around 400 ppm, and still rising.

Dutton says even if current climate negotiations succeed in limiting global temperature rise to 2oC, that could still be enough to trigger that level of sea rise.

"The decisions we make now about where we want to be in 2100 commit us on a pathway where we can’t go back," Dutton told Scientific American. "Once these ice sheets start to melt, the changes become irreversible."

Global sea levels have been steadily rising since the 19th century, with the world's oceans now 200mm (0.2m) higher than they were in 1870. Currently, global sea levels are rising at a rate of just over 3mm a year.

The research was published in the latest issue of Science.

SOURCE: University of Florida | Science Magazine | Scientific American

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