Climate change: a problem with very specific time scales Hervé Le Treut
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Climate change: a problem with very specific time scales
Hervé Le Treut
LMD
Laboratoire de Météorologie Dynamique (CNRS/ Ecole Normale Supérieure /Ecole Polytechnique/Université Paris 6)
Institut Pierre Simon Laplace
Académie des Sciences
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Our planet is confronted to a situation which was never encountered in the history of human civilizations:
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The perturbation has increased sharply after 1950
Energy use: oil, coal and natural gas account for most of the increase
19001950
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The consequences have been anticipated by the scientistson the basis of physical models (results of IPCC 1990
and IPCC 1995, compared to subsequent measurements)
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They have been detected only recently ….
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They will have lasting consequences, ….
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Even at a very long time scale ….
Zero-emissions after 2100:
Effect on temperature and sea-level rise
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Adaptation to climate impacts: the necessary interactions between decision making and
scientific assessment
Hervé Le Treut
LMD
Laboratoire de Météorologie Dynamique (CNRS/ Ecole Normale Supérieure /Ecole Polytechnique/Université Paris 6)
Institut Pierre Simon Laplace
Académie des Sciences
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Assessing the impacts of climate changeis 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
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Space-borne instruments
1.8 mm/an
In situ measurements
Observed rise: 3.3 mm/year since 1993
Satellite measurements
The rise is not evenly distributed! Yellow/red blue
1993 2006
Assessing current evolutions provides a necessary insight into future evolutions. The example of sea-level rise.
A. Cazenave (LEGOS/ Toulouse)
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Assessing current evolutions provides a necessary complement to modeling approaches. A summary of current physical and biological observations by IPCC Working Group II.