The melting of the Antarctic and Greenland ice sheets has
raised sea levels by 11.1 millimetres since 1992, a fifth of
the total rise which threatens low-lying regions around the
globe, a new study published today said.
The results of the study involving 47 researchers from 26
laboratories which was supported by the European Space Agency
and the National Aeronautics and Space Administration give
the most accurate measurements of ice loss to date, they said
in the journal Science.
Two thirds of the ice loss was in Greenland which is losing
five times as much ice as in the 1990s, and the remainder was
Together, the two receding ice sheets are now adding 0.95mm
to sea levels a year compared to 0.27mm per year in the
1990s, the study said.
There have been at least 29 studies on ice sheet mass since
1998 which arrive at an average for the melt's contribution
to sea level rises of around 1mm a year, the study's leader
Andrew Shepherd told reporters.
The researchers used 10 different satellites to measure the
shape, speed and weight of the ice sheets from space, as well
as ground observations.
Past ice loss assessments typically used just one of those
techniques, said Shepherd, a professor at the University of
The results come as representatives from nearly 200 countries
are in Qatar trying to reach a new global agreement on
cutting greenhouse gas emissions, which are widely held
responsible for causing global warming.
"The study effectively ends 20 years of uncertainty over the
perception of our community. It provides a single climate
record for people to use rather than the 40 or 50 which
existed before this paper," Shepherd said.
In 2007 scientists on the Intergovernmental Panel on Climate
Change (IPCC) published their fourth report to assess
scientific and technical information on climate change and
its effects. The next IPCC report is due out next year.
The fourth report estimated a total global sea level rise of
2mm a year from the early 1990s to 2011, while research by
the Potsdam Institute for Climate Impact Research this week
estimated the rise has been as much as 3.2mm a year over the
"We have pinpointed the areas of ice sheets where people
should be concerned," Shepherd said. "There are parts of
Antarctic where the ice is not behaving in a normal way. It
is unstable and its sea level contribution is rising
Greenland even more so," he said.
"That allows us to say to people who build models for future
climate projections, 'these are the areas you should
concentrate on'," he said, adding that continued monitoring
of ice sheets is necessary.
The researchers did not make predictions about how much sea
levels were likely to rise this century, saying it was not
the aim of the project.
The IPCC has said seas could rise by between 18 and 59 cm
this century, not counting the possible acceleration of the
melt of the Greenland and Antarctic ice sheets that could add
more still water to the oceans. The Potsdam study places that
figure even higher at between 50cm and a metre this century.