Future Climate

The earth's climate may change in the future due to the same factors that influence the present climate: (1) natural external changes, such as changes in volcanic activity or, perhaps, small changes in solar radiation; (2) human activities, such as changes in atmospheric greenhouse gases, changes in atmospheric aerosol loading, and changes in land use; and (3) internal variability of the coupled atmosphere-ocean-land-biosphere system. Within CCR, we are focusing our research on the role of human activities and the role of internal variability, and, very importantly, the coupling between human-caused changes in base-state climate and possible resulting changes in climate variability.

Human activities. We are using coupled atmosphere-ocean models to simulate the climate's response to increasing levels of atmospheric carbon dioxide concentration. One important aspect of this research is to understand the cause of observed and simulated changes in the climatology of the tropical Pacific Ocean, because changes in this sector may be related to changes in El Nino/ Southern Oscillation (ENSO) and to changes world-wide through dynamical linkages between the atmospheric circulation of the tropics and middle latitudes. Another important aspect of our studies is to examine simulated changes in the ocean's thermohaline circulation, the so-called ocean "conveyor belt" that results in a net transport of heat from the equatorial regions toward middle and high latitudes.

We are also studying how changes in land-use, specifically, changes in the area of tropical forests, might influence both the atmospheric circulation and the circulation of the oceans adjacent to the deforested land. In more realistic scenarios, we will be examining the possible combined effects of deforestation and greenhouse warming.

Future climate change and changes of variability. Changes in the base state of the climate, for example, the strength of the oceanic trade winds, the degree of tropical upwelling, the location and strength of the Intertropical Convergence Zone, and the temperature of the ocean may influence the frequency and magnitude of El Nino. In some of our preliminary work, we find that increasing the atmospheric carbon dioxide concetration leads to decreased strength of El Nino.

Changes in terrestrial and marine ecosystems. We are in the process of coupling terrestrial and marine ecosystem models with an atmosphere-ocean model in order to simulate possible changes in ecosystems in future global change scenarios involving greenhouse gas increase and changes in land use. (see ecosystems/climate).