INTEGRATING COMPONENTS OF THE EARTH SYSTEM TO MODEL GLOBAL CLIMATE CHANGES: IMPLICATIONS FOR THE SIMULATION OF THE CLIMATE OF THE NEXT MILLION YEARS
Laboratoire mixte CEA-CNRS-UVSQ, France
The climate system is complex because it is made up of several components (atmosphere, ocean, sea ice, continental surface, ice sheets), each of which has its own response time. The paleoclimate record provides ample evidence that these components interact nonlinearly with each other and also with global biogeochemical cycles, which drive greenhouse gas concentration in the atmosphere.
Forecasting the evolution of future climate is therefore an extremely complex problem. In addition, since the nineteenth century, human activities are releasing great quantities of greenhouse gases (CO
2,CH4, CFC, etc.) into the atmosphere. As a consequence, the atmospheric content of these gases has tremendously increased. As they have a strong greenhouse effect, their concentration is now large enough to perturb the natural evolution of the earth’s climate.
In this paper, we shall review the strategy which has been used to develop and validate tools that would allow to simulate the future long-term behaviour of the Earth’s climate. This strategy rests on two complementary approaches: developing numerical models of the climate system and validating them by comparing their output with present-day meteorological data and paleoclimatic reconstructions. We shall then evaluate the methods available to simulate climate at the regional scale and the major uncertainties that must be solved to reasonable estimate the long-term evolution of a region, which would receive a geological repository for nuclear wastes. Modelling the general circulation of the mosphere It was realised as early as the Mid twentieth century that modelling the global climate system was the only approach allowing to forecast the long-term (~ 10 6 years) evolution of the earth’s climate.