Oceans Warming and Rising

Julio Godoy*

BERLIN, Dec 21 (IPS/IFEJ) - 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 on oceans.

"The semi-empirical 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 100 years.

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 

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 said.

(*This story is part of a series of features on sustainable 
development by IPS - Inter Press Service and IFEJ - International 
Federation of Environmental Journalists.)