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Nombre de programmes trouvés : 76
Conférences

le (28m58s)

Modelling Forced and Internal Climate Variability During the Last Millennium

At hemispheric scale, the surface temperature is strongly influenced by the 28 variations of the natural (solar and volcanic) and anthropogenic (land-use, sulphate aerosols, greenhouse gas concentrations) forcings. By contrast, at regional scale, the internal variability, which is purely due to the internal dynamics of the climate system, can mask the forced response. As a consequence, before the 20th century, cold or warm periods are rarely global, homogenous phenomena. Furthermore, the response to the forcing could be associated with changes in the frequency of some modes of variability. This interplay between the response of the climate system to the various ...
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Conférences

le (28m50s)

International Negociations on Climate Change: How to Take Advantage of Risk Aversion to Improve the Conditions for the Emergence of a Consensus

Climate change is one of the best examples of global environmental problems. Countries are conscious that they have to find a solution to this global problem at the international level. Negotiations on climate change started more than 15 years ago with the signature of the United Nations Framework Convention on Climate Change. Since then, the process went through a series of conferences and protocols. Part of this process, the Kyoto protocol constitutes a major step since it designed country-specific targets defined in terms of CO2 emissions abatement. The fact is that we should not speak about an international environmental agreement ...
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Conférences

le (28m6s)

Global Climate Change: Past and Future

My presentation will begin with a review of the now-solid evidence for a human influence on the climate of recent decades. Such evidence includes instrumental measurements available for the past two centuries, paleoclimate observations spanning more than a millennium, and comparisons of the predictions from computer models with observed patterns of climate change. I will then address how the study of paleoclimate can inform our assessments of the potential future impacts of human-induced climate change.
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Conférences

le (28m0s)

Climate Models: learning from the Past Long-Term Climate Variability

Projections of future climate change rely on global climate models. Such models simulate the dynamics and physics of the coupled atmosphere-ocean system and move towards models of the full Earth system. These models are evaluated on the present day mean climate as well as on climate variability over the last century. Although climate models agree on the overall patterns of future climate change, discrepancies are still displayed between models, both in amplitude and at the regional scale (e.g., IPCC AR5 (2007)). Past climates offer an unique opportunity to evaluate climate models on climate conditions different from the present-day conditions ...
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Conférences

le (27m2s)

The Impacts of Climate Change on Continental Ecosystems

Climate change will deeply modify the ecophysiological functioningof plants, by creating a set of conditions which could be more favourable (in the sense of biomass production) or not. Among the first, the increase ofatmospheric CO2 will stimulate the photosynthesis (with levels depending upon plants and conditions), with a result of a potential increase in biomass up to 20 % in some cases. Warmer temperatures will also generally be favourable to most of the physiological processes, up to an optimum above which the risk of detrimental or lethal values exists. The (almost) generalized advance in phenology (calendar of development stages) will ...
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Conférences

le (24m29s)

Detection and Attribution of Climate Change to Different Causes

According to the last IPCC report, the most part of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This statement relies on a long process of demonstration that consisted in evaluating the ability of the successive generations of climate models to reproduce and interpret the climate variability of the last decades. The more and more numerous statistical analyses aiming at detecting and attributing climate change to natural and anthropogenic causes have reinforced the assessment of experts. The recent detection and attribution studies of observed ...
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