Séminaire
Because the solar luminosity increases over geological timescales, Earth climate is expected to warm, increasing water evaporation which, in turn, enhances the atmospheric greenhouse effect. Above a certain critical insolation, this destabilizing greenhouse feedback can "runaway" until all the oceans are evaporated (the so-called runaway greenhouse instability). Through increases in stratospheric humidity, warming may also cause oceans to escape to space before the runaway greenhouse occurs. The critical insolation thresholds for these processes, however, remain uncertain because they have so far been evaluated with unidimensional models that cannot account for the dynamical and cloud feedback effects that are key stabilizing features of Earth's climate. With more than 1000 exoplanets discovered, the need to understand these processes goes beyond the boundaries of the Earth, as it is the main way to know which planet can harbor liquid water... with many implications.
Here I will present the generic version of the LMDZ global climate model that I have been developing specifically to quantify the climate response of terrestrial planets to increased insolation in hot and possibly extremely moist atmospheres. I will also show the application of this model to various extreme planetary climate questions: when will the Earth lose its oceans, did Venus ever harbor any surface liquid water, and what happens when planetary tides have been strong enough to synchronize the rotation of the planet with its orbit, leaving one hemisphere permanently sunlit and the other in eternal darkness?
MP Lefebvre (0144272799)