|
March
2, 2007
HEAT
WAVE ON THE TOP OF THE WORLD
The French
Intergovernmental
Panel on Climate Change (IPPC, or GIEC in French) has just announced
the
conclusions of its 4th report, which restates that global warming has
increased
the average temperature by 0.74°C over the last century.
However, there is very
little information about some parts of the planet, such as central Asia. A new study by French
researchers from the
Laboratory of Glaciology and Geophysics of the Environment (LGGE, CNRS
/
Université Joseph Fourier, Grenoble, France) and the
Laboratory of Sciences of
the Climate and the Environment (LSCE / IPSL, CEA / CNRS /
Université de
Versailles Saint-Quentin, France), in collaboration with Chinese,
Russian and American
researchers, proves that the recent warming has also affected the ice
cap on
Mount Everest, in the heart of the Himalayas. This result was published
on
February 7, 2007 in the European journal Climate
of the Past.
Relatively little is
known about
climate change in the Himalayas
and the
Tibetan plateau. There are very few meteorological stations, and
instrumental
records from glaciers, lakes or tree growth rings are rare and
difficult to
interpret. However, in 2001 and 2002, Chinese scientists drilled three
ice
cores in the eastern summit of the East Rongbuk glacier that covers the
north
pass of Mount Everest,
at 6518 meters above
sea level. These ice cores were analyzed in collaboration with the LGGE
and the
LSCE, and they have shown that a new climate marker exists, the ice
core gas
content, which can reconstruct the changes in summer temperatures on
this very
high site.
At these altitudes,
the surface
snow partially melts in the summer and the melt water percolates1
through the
snow cover to refreeze deep down. This process affects the density and
size of
air bubbles contained in the ice, that is, its gas content. So the gas
content
is directly related to the intensity of the summer ice melt. By
measuring
accurately the gas content throughout two of the three ice cores taken
from the
top of Everest, researchers have been able to follow the changes over
time,
going right back to 2,000 years ago. They noted a very marked decrease
in the
quantity of gas trapped in the 20th century ice, compared with the
content in
older ice, which reflects recent increases in the summer melts on the
glacier
surface. Although the team has not as yet been able to quantify exactly
the
temperature change over time using this new marker of trapped gas,
their
research clearly shows that global warming has also affected the ice
cap on top
of the world.
##
Contact:
Monica
McCarthy
CNRS
33-104-496-5191
monica.mccarthy@crns-dir.fr
This text derived from:
http://www.cnrs.fr/index.html
Recommend this Article to a Friend
Back to: News |