Sea level rise may be even more urgent than previously thought

A new study has suggested that as a result of global warming, sea level rise may be even more urgent than previously thought.

According to a report in Nature News, Robert Kopp, a palaeoclimatologist at Princeton University in New Jersey, and his colleagues examined sea level rise during the most recent previous interglacial stage, about 125,000 years ago.

It was a time when the climate was similar to that predicted for our future, with average polar temperatures about 3-5 degrees Celsius warmer than now.

Other studies have looked at this era, but most focused on sea level changes in only a few locales and local changes may not fully reflect global changes.

Sea level can rise, for example, if the land is subsiding.

It can also be affected by changes in the mass distribution of Earth. For example, according to Kopp, ice-age glaciers have enough gravity to pull water slightly polewards.

When the glaciers melt, water moves back towards the Equator.

To adjust for such effects, Kopp's team compiled sea-level data from over 30 sites across the globe.

"We could go to a lot of different places and look at coral reefs or intertidal sediments or beaches that are now stranded above sea level, and build a reasonably large database of sea-level indicators," said Kopp.

The team reports that the sea probably rose about 6.6-9.4 m above present-day levels during the previous period between ice ages.

When it was at roughly its present level, the average rate of rise was probably 56-92 cm a century.

"That is faster than the current rate of sea level rise by a factor of about two or three," Kopp said, warning that if the poles warm as expected, a similar acceleration in sea-level rise might occur in future.

According to Peter Clark, a geologist at Oregon State University in Corvallis, if the world warms up to levels comparable to those 125,000 years ago, "we can expect a large fraction of the Greenland ice sheet and some part of the Antarctic ice sheet, mostly likely West Antarctica, to melt. That's clearly in sight with where we're heading."