Tuesday, 11 January 2000: 9:00 AM
Surface and satellite-based observations show decrease in
Northern Hemisphere sea ice extent during the past 25
years. We compare these observed trends to control and
transient (forced by observed CO2 and sulfate
aerosols) runs from the Geophysical Fluid Dynamics
Laboratory and Hadley Centre climate models. The estimates
of natural variability are based on the control
integrations. The observed decrease is far larger than would
be expected by natural climate variations. The decrease
agrees with a statistically significant retreat in sea ice
extent during the second half of the century, mostly during
the last 25 years, predicted by the forced integrations of
both models. Therefore, we conclude that the observed sea
ice decrease could be a fingerprint of anthropogenic global
warming. Both models predict continued sea ice decreases in
the next century.
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