Fingerprint of global warming? Press release from the Nansen Environmental and Remote Sensing Center, 950324. Click here for a text file.

The sea ice in the Arctic is melting,
is this a sign of global warming?


With the increasing emissions of greenhouse gases into the atmosphere, we are approaching the period where we will note and observe global warming. Simulations with global climate models in various climate research centers around the world show that around the turn-of-the-century we can prove that global warming is indeed occurring. The warming will first be noticed in Arctic regions, for example, in decreases in the sea ice extent. By then the human-induced greenhouse gases will bring about a signal in the atmosphere greater than the natural climate variability. Atmospheric warming will have far-reaching and dramatic consequences: for example, ocean circulation will be changed, the global sea ice cover will decrease, the distribution of precipitation will be different, and the sea level will rise. Thus everyone on the planet is participating in a completely uncontrolled, long-term, global experiment which will bring about dramatic ecological and economic changes for the world's people today and for our descendants' future.

At the Nansen Environmental and Remote Sensing Center, affiliated with the University of Bergen, researchers have for several years used satellites to monitor potential climate changes. In particular, they have studied changes in the global sea ice cover using two American satellite systems, the NASA Nimbus-7 and the Defense Meteorological Satellite Program (DMSP). At present, global observations are made daily from the so-called passive microwave sensors which measure radiation emitted from the ocean and ice independent of weather and darkness. The Nimbus-7 satellite was launched in fall 1978 and operated until 1987. It was then replaced by the DMSP satellite, which is still operating today. Professor Ola M. Johannessen at the Nansen Center has worked with these data over a long period, and he was a member the NASA Nimbus-7 team at its launch in 1978.

Professor Johannessen, with research colleague Dr. Martin Miles and student Einar Bjørgo, has just now completed an analysis of the global ice cover variations from this unique data set, which covers a 16-year period from 1978-94. The results are that the extent and area of sea ice have decreased about 5.5% over the period in the Arctic. The conditions in the Antarctic are stable and no trend can be measured. The 5.5% decrease in the Arctic over 16 years represents an area twice the size of Norway. Less ice in the Arctic means greater heat exchange between ocean and atmosphere, with consequences for the weather in Norway and Europe. On the other hand, less ice means easier transport conditions for ships (for example through the Northeast passage) and easier exploration and recovery of potential gas and oil reserves in the polar regions.

The results of the researchers at the Nansen Center, which are submitted for publication, qualitatively support the predictions from the climate models, namely that it is in the Arctic that the first "fingerprints" of the anticipated global warming will be found. The analyses of the global ice cover using satellites also show the potential that satellites have to monitor environment and climate on our planet.

Plot of Arctic sea ice area .
Plot of Arctic sea ice area anomalies with trend .

For further information, contact:
    Prof. Ola M. Johannessen
    Nansen Environmental and Remote Sensing Center
    Edvard Griegs vei 3a
    N-5037 Bergen-Solheimsviken
    Norway

    Phone:  +47 55 29 72 88 (Office)
            +47 55 22 69 23 (Home)
    Fax:    +47 55 20 00 50
    E-mail: Ola.Johannessen@nrsc.no
    URL:    http://www.nrsc.no:8001/
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