Transcript Presentation

Climate change: a problem with very
specific time scales
Hervé Le Treut
Laboratoire de Météorologie Dynamique (CNRS/ Ecole
Normale Supérieure /Ecole Polytechnique/Université
Paris 6)
Institut Pierre Simon Laplace
Académie des Sciences
LMD
Our planet is confronted to a situation which was never
encountered in the history of human civilizations:
The perturbation has
increased sharply
after 1950
1950
1900
Energy use: oil, coal and
natural gas account for most of
the increase
The consequences have been anticipated by the scientists
on the basis of physical models (results of IPCC 1990
and IPCC 1995, compared to subsequent measurements)
They have been detected only recently ….
They will have lasting consequences, ….
Even at a very long time scale ….
Zero-emissions after
2100:
Effect on temperature
and sea-level rise
Adaptation to climate impacts: the necessary
interactions between decision making and
scientific assessment
Hervé Le Treut
Laboratoire de Météorologie Dynamique (CNRS/ Ecole
Normale Supérieure /Ecole Polytechnique/Université
Paris 6)
Institut Pierre Simon Laplace
Académie des Sciences
LMD
Assessing the impacts of climate change
is a process confronted with many difficulties:
-
The predicted amplitude of future climate change lies within a certain
uncertainty range
-
Potential impacts are very different in nature: heat waves, droughts, cyclone
intensification, ocean circulation changes, sea-level rise, modification of
ecosystems and loss of biodiversity, health, economic activities
-
The climate system is non-linear and may evolve abruptly when certain
(unprecisely known) thresholds are reached
-
The consequences of climate changes also depend on other anthropogenic
factors: direct modification of the biodiversity, water management, soil use,
geopolitical tensions, …
A constant interplay between scientific measurements and decision making is
necessary to define and revise continuously an adaptation stategy to climate
change
Assessing current evolutions provides a necessary insight
into future evolutions. The example of sea-level rise.
Satellite
measurements
Space-borne
instruments
In situ
measurements
Observed rise:
3.3 mm/year since 1993
1.8 mm/an
A. Cazenave (LEGOS/ Toulouse)
1993
2006
The rise is not evenly distributed!
Yellow/red
blue
Assessing current evolutions provides a necessary complement to modeling
approaches.
A summary of current physical and biological observations by IPCC
Working Group II.