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Olivier Boucher is one of
the six co-authors, all researchers within the international scientific
community, of an article published in the journal Science on May
16, 2003, concerning climate change and related issues. He is a researcher
at the "Laboratoire d’0ptique Atmosphérique" (CNRS
- Université des Sciences et Technologie of Lille) and a member
of the "Groupement Intergouvernemental d’Experts sur l’Evolution
du Climat" (GIEC)* . By using twenty recently published
scientific articles as references, he focuses especially on the effect
of aerosols that cool the climate compared to greenhouse gases that lead
to warming. This synthesis makes it possible to better understand future
directions to be adopted by researchers on measuring the effects of aerosols.
Global warming is attributed to an increase in the concentration of greenhouse
gases that lead to a positive perturbation of the radiative balance or
"positive radiative forcing." However, aerosols (atmospheric
particles) of human origin cool the climate by reflecting incoming solar
radiation and by modifying cloud properties. This climatic disturbance
resulting from aerosols is very difficult to measure. It is estimated
according to two methods: direct and inverse. The direct methods are based
on an estimation of the anthropogenic aerosol quantities present in the
atmosphere and their physical and optical properties. The inverse methods
are based on the assumption that we can explain global warming today by
overall radiative perturbations. Thus, radiative forcing is calculated
on the basis of the total radiative forcing necessary to explain the present
warming, after the other known radiative forcings (including that of greenhouse
gases) have been deducted.
There is, however, inconsistency between the high radiative forcing values
obtained by direct methods and the low values derived using inverse methods.
Either the first are false or the estimates resulting from the inverse
methods are artificially low because they do not take into account uncertainties.
For Olivier Boucher, "It would not be wise to accept the first explanation.
We must continue working on direct estimates of the effect of aerosols
and try to find out ways to remedy this inconsistency." In fact,
climate forecasts would be even less accurate if the uncertainties related
to the radiative effects of aerosols were actually taken into account.
If the radiative forcing of aerosols is very negative, climatic sensitivity
will be higher and future global warming may be even greater.
At the "Laboratoire d’Optique Atmosphérique," research
is aimed at reducing the uncertainties about the climatic effects of aerosols
by simulations of the global distribution of aerosols and observations
from outer space of aerosols and clouds. The LOA will thus be participating
in the AQUA-train project in 2004, involving a series of Earth observation
satellites flying in formation and taking many different types of measurements.
*
Documents produced by the GIEC act as references within the framework
of international negotiations on greenhouse gases such as the Kyoto Protocol,
etc.
Researcher
contact:
Olivier Boucher
Laboratoire d’Optique Atmosphérique
Tel: +33 3 20 43 62 30
E-mail: boucher@loaser.univ-lille1.fr
Press contact :
Magali Sarazin
Tel: +33 1 44 96 46 06
E-mail : magali.sarazin@cnrs-dir.fr
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