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Que penser de la thèse du "réchauffement global d’origine anthropique" ?

22 mars 2010, 11:52, par Philippe de Casabianca

Non, le volcanisme n’est pas ignoré parmi les climatologues.

cf Turning the Tide on Climate Change (2009) (http://www.cefic.org/files/publications/Book-climate-change/) page 25 :

"Human activities are reinforcing the greenhouse effect
The warming trends of the last century, considered as much stronger than
climate fluctuations of the past two thousand years, have appeared together
with the sharp increases in atmospheric concentrations of the greenhouse
gases CO2 and methane. Those increases have no precedent in the preceding
million years. Indeed the rise in atmospheric CO2 due to human activities, most
of which has taken place in the last 50 years, is stronger and much faster than
the natural rise of CO2 that took place over a period of more than 5,000 years
at the end of the last ice age.

Attributing global warming since 1950 to the rise of CO2 is not simply a matter
of correlation. The well-established physics of the transfer of radiation in the
atmosphere tells us that although it is not the only factor affecting climate, this
rapid reinforcement of the greenhouse effect perturbs Earth’s energy balance.
As a result, mean surface temperature is rising

What about other natural climate factors ?
Variations of the Sun have been too weak to explain the climate changes of
the past century, but what about the “parasol effect” ? The planet’s albedo (the
fraction of the Sun’s incoming radiation reflected or scattered back to space)
determines what fraction of incoming solar radiation is converted into heat.

Volcanic eruptions increase the amount of reflecting particles in the stratosphere
(altitude 10-50 km). Powerful eruptions have caused global cooling, as in 1816,
the “year without a summer” that followed the 1815 eruption of Tambora in
Indonesia. The eruption of Mount Pinatubo in the Philippines in 1991 led to a
brief pause in global warming.
The effects of such eruptions can be strong, but
they last less than two years, while reinforcement of the greenhouse effect has
been growing year after year

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