Data from satellites is showing that sea-level rises and polar
ice-melting might be worse than earlier thought, a leading oceanographer
said on Monday.
Sea levels, rising at 1 millimetre a year before the industrial
revolution, are now rising by 3 millimetres a year because of a
combination of global warming, polar ice-melting and long natural cycles
of sea level change.
"All indications are that it's going to get faster," said Eric
Lindstrom, head of oceanography at the National Aeronautics and Space
Administration (NASA), told Reuters on the sidelines of a global oceans
conference in Hobart.
Rapid advances in science in the past five years on polar ice-sheet
dynamics had yet to filter through into scientific models, Lindstrom
said.
He also pointed to huge splits in Antarctic ice shelves in 2002, then
seen as once-in-100-year events that created icebergs bigger than some
small countries.
The mega icebergs were first thought not to affect global sea levels
because the ice broke off from shelves already floating on the surface
of the ocean.
But the disintegration of ice shelves that had blocked the flow of ice
from the Antarctic continent could allow sudden flows by glaciers into
the ocean, raising sea-levels.
"What we're learning is that ice isn't slow. Things can happen fast,"
Lindstrom said.
"If the (polar) ice sheets really get involved, then we're talking tens
of metres of sea level -- that could really start to swamp low-lying
countries," he said.
A report by the UN climate panel released last month cited six models
with core projections of sea level rises ranging from 28 to 43 cms
(11.0-16.9 inches) by 2100.
The Intergovernmental Panel on Climate Change also said temperatures
were likely to rise by 2-4.5 Celsius (3.6-8.1 Fahrenheit) above
pre-industrial levels if carbon dioxide concentrations are kept at 550
parts per million in the atmosphere, against about 380 now. The "best
estimate" for the rise is about 3C (5.4F).
The report, which brought together 2,500 researchers from more than 130
nations, said Antarctica was likely to stay too cold for wide surface
melting and is expected to gain in mass due to more snow.
(Por Michael Byrnes,
Planet Ark, 12/03/2007)