Geoökologisches Kolloquium SS 2003

Alle Termine

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Dr. George Kukla
Lamont Doherty Earth Observatory of Columbia University, Palisades, NY, USA
Donnerstag, 03.07.2003 18:00 H6

Foxy trick of mother nature: into a glacial through global warming

Frequency of paleoclimatic variations matches that of the elements of
earth\'s circum-solar orbit. It is generally accepted that the seasonal
and latitudinal redistribution of solar energy reaching the Earth controls
the state of global climate. Correlation of paleoclimatic evidence with
orbital changes shows that the build-up of polar ice accelerates at
times of low obliquity and early winter perihelion. Paleoclimatic data
also show that this orbital configuration favors the warming of tropical
oceans, increased transfer of water vapor to the high latitudes and
increased frequency of El Nino, which becomes dominant over La
Nina anomalies. Because the oceans in low latitudes, which are
warming, form the largest portion of the planet, it is highly probable
that the areally averaged global surface temperature during the first
several millennia of the glacial ice build-up was increasing and
consequently, that the glacials started with global warming.

Today the orbital configuration, although less extreme, is in principle
similar to the one at the start of the last glacial, 115 thousand years
ago. Frequency of El Nino is increasing, that of La Nina decreasing,
ice on top of Antarctica and Greenland is growing and northern North
Atlantic is getting fresher. Obliquity is also dropping and the insolation
to central Arctic is slowly decreasing. These current trends, when
compared with the paleoclimatic evidence, raise important questions
about near future climates:

1) What is the proportion of natural and artificial components of
the ongoing climate change?
2) Is the anthropogenic impact on climate change properly
detected by globally averaged temperatures? Does IPCC and media
have it right?
3) And, most importantly: is the man made CO2 mitigating or
accelerating the natural shift into a glacial?


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