Warming And Rising
By Julio Godoy
24 December, 2006
Inter Press Service
Ocean levels will rise faster
than expected if greenhouse gas emissions continue to rise, a leading
German researcher warns.
Using data from the U.S.
National Aeronautics and Space Administration (NASA), Stefan Rahmstorf,
professor of physics of the oceans at the University of Potsdam near
Berlin estimates that sea level could rise 140 cm by 2100.
Rahmstorf, member of the German Advisory Council on Global Change, is
considered a leading European researcher on global warming and its effect
model we used to process NASA data showed a proportional constant sea
level rise of 3.4 mm per year per degree Celsius," Rahmstorf told
IPS. "Then we applied this constant proportionality to future earth
surface warming scenarios of the Intergovernmental Panel on Climate
Change (IPPC), and came to estimate that by the year 2100, sea level
could rise between 50 and 140 cm above the level measured in 1990."
Through the 20th century,
global warming led to an average 20cm rise in sea level. But most computer
models of climate change used at present significantly underestimate
sea level rise, Rahmstorf said. "Future projections of sea level
based on these climate models are therefore unreliable."
Currently, sea level is rising
at three cm per decade, faster than projected in the scenarios of the
IPCC Third Assessment Report, Rahmstorf added.
The IPCC, an intergovernmental
team of scientists carrying out a wide range of research related to
climate change, was established in 1988 by the World Meteorological
Organisation and the United Nations Environmental Programme. The IPCC
aims to assess scientific, technical and socio-economic information
relevant for understanding of climate change, its potential impact,
and options for adaptation and mitigation.
Scientific research has found
that industrial activities have produced greenhouse gas emissions considerably
higher than levels observed before the industrial revolution.
Concentration of carbon dioxide
(CO2), the most potent of greenhouse gases, has risen from about 280
parts per million (ppm) in the atmosphere in the year 1750 to about
380 ppm today.
This rise is primarily due
to the burning of fossil fuels, and to a lesser extent, deforestation.
Scientists estimate that if the present emissions trend continues, the
atmosphere could heat up by about five 5 degrees Celsius by 2100.
Studies by the Potsdam Institute
for Climate Impact Research suggest that this would roughly be the temperature
difference between an ice age and a warm stage. But while the rise of
average temperatures by some five degrees between the last great ice
age and today took 5,000 years, the new global warming would need only
Rahmstorf acknowledged that
forecasts of global warming and its effects on sea levels continue to
be marked by uncertainty. "The fact that we get such different
estimates using different methods shows how uncertain our sea level
forecasts still are," Rahmstorf told IPS.
A major reason for the uncertainty
is the behaviour of the large ice sheets in Greenland and Antarctica.
A likely consequence of a
massive melting of the ice masses on the North Pole could be the breakdown
of the North Atlantic Current (NAC). The NAC is the northern extension
of the Gulf Stream, and constitutes a warm water current flowing between
Britain and Iceland. This has considerable impact in moderating the
North European and Scandinavian climate.
"One critical factor
for the continuation of this current is the amount of fresh water that
enters the Northern Atlantic region in the future," Rahmstorf said.
"This will depend in large part on the speed at which Greenland's
ice sheet melts."
Rahmstorf, who earlier this
year co-authored a research paper titled 'The Future Oceans -- Warming
Up, Rising High, Turning Sour' said that reliable prediction on the
risk of a total stoppage of deepwater formation in the Northern Atlantic
is not possible given present knowledge.
But he pointed out that experts
have evaluated that risk at more than 50 percent if global warming is
between three and five degrees.
Rahmstorf said greenhouse
gases emissions are also increasing the acidity of oceans. "In
the atmosphere carbon dioxide does not react with other gases, but in
the ocean it dissolves, contributing to the acidification of seawater,"
Rahmstorf said. This acidity is a serious threat to marine biodiversity.
"There is a good chance
to avoid such dangerous climate change if global warming caused by human
activities is limited to two degrees in the coming decades," Rahmstorf
(*This story is part of a
series of features on sustainable development by IPS - Inter Press Service
and IFEJ - International Federation of Environmental Journalists.)
Copyright © 2006 IPS-Inter
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