Paleoclimate
Paleoclimate research at the Center for Climate Systems Research (CCSR) has the aim of better understanding the evolution of the Earth's atmosphere, oceans, biosphere and cryosphere, from the depths of the geologic past to periods only slightly before the beginning of the 20th century and the development of modern meteorological instruments. s paleoclimate efforts are primarily centered on the use of global climate models to simulate climates of the past. However, we are involved in many collaborative efforts that bring together both data and modeling techniques to provide the broadest possible view of Earth's climate history.
Paleoclimate modeling helps us to better quantify the Earth's changing climate through time, especially helping us to understand the forces that drive climate change and the processes the operate when climates are either warmer or colder at present. In turn, we use paleoclimate simulations to validate the ability of computer climate models to accurately represent a wide range of climatic conditions. The ability to simulate climate changes that occurred in the past strengthens our confidence in the conclusions drawn from simulations of future climate.
Commonly, GCM simulations are used to corroborate or refute hypotheses first drawn from paleoclimate data or to sort out conflicting data interpretations. However, since GCMs are capable of simulating numerous climate variables that are largely unattainable from the geologic record (e.g., cloud distribution, wind patterns, energy transports and radiative fluxes), they offer insight into a broad range of complex processes. Models also provide complete global coverage while data provide unequal, perhaps biased, coverage of Earth's surface. Finally, because paleoclimate simulations can, to a certain degree, be verified, they help us test and improve developmental GCM formulations.
Numerous time periods throughout Earth's history have been simulated by CCSR and NASA/GISS researchers. The climates of the Last Glacial Maximum (21 Kyr) and the Holocene (the last 10,000 years) have available vast amounts of data from both land and oceans. Thus, they provide an excellent validation set for climate models as well as a test of model sensitivity to carbon dioxide change and to variations in Earth's orbit. Climates of much older time periods are also simulated and explored at CCSR, from the warmth of the middle Pliocene (3 Myr) - the most recent prior period of extreme global warming in Earth's past - to the snowball earth episodes of the Neoproterozoic (750 Myr and 600 Myr ago). Such ancient climates test the sensitivity of the GCM to large changes in geography, greenhouse gases, solar luminosity and ocean heat transports.
