Cooperative Institute for Climate Science: Modeling the Earth System
Although the Cooperative Institute for Climate Science (CICS) is the newest NOAA Joint Institute (founded only in 2003) it builds on a long tradition of collaboration between NOAA’s Geophysical Fluid Dynamics Lab and Princeton University in climate science. For over thirty five years, GFDL and Princeton have collaborated through the Atmospheric and Oceanic Sciences (AOS) Program to build cutting edge models of the climate system and to use these models to understand and predict the climate. The distinguished group of researchers involved includes three members of the National Academy of Science, George Philander at Princeton and Isaac Held at GFDL. Research within this collaboration has traditionally focused on two themes:
Understanding processes, forcings and feedbacks on the physical climate system: What processes play an important role in controlling earth’s climate? How well do we understand these processes and their interactions? When we try to model these processes, how well do our results compare with data? AOS and CICS postdocs and graduate students have played a key role in addressing these questions. Over the years, postdoctoral fellows in the AOS program have worked to implement new models of sea ice within the GFDL coupled model, help to develop and test new parameterizations of ocean eddies, examined the roles of aerosols in climate, and performed simulations of past climates, with an eye to elucidating key mechanisms within the climate system. Current postdocs and graduate students are helping us to understand how changes in aerosols affect clouds and weather, analyzing modes of variability such as El Nino and the North Atlantic Oscillation, and helping to develop conceptu al models of hurricanes.
Biogeochemical cycling: Humans now play a major role in biospheric processes. Human additions of fixed nitrogen to the biosphere are the same size as the natural cycle. Human contributions of carbon to the atmosphere (6GtC) are of the same order of magnitude as the natural year-to-year variability in carbon exchange with the oceans and land plants. CICS director Jorge Sarmiento and Princeton professor Steve Pacala have played a leading role in developing models of how elements like carbon and nitrogen cycle through the biosphere. These models are currently being implemented in a range of circulation models within GFDL by both CICS and GFDL scientists to address key questions. For example, it is known that the ocean is a major sink of carbon dioxide, absorbing approximately 1/3 of the carbon put into the atmosphere each year. Figure 1 shows both observational estimates of the inventory of this carbon (the result of a community-wide collaboration in which both NOA A and CICS scientists have played a leading role) and three models which reproduce most of the main features of the observations.
In the next few years, CICS also plans to answer NOAA’s call to extend the applicability of climate models by applying them both to the past, where long records of climate change are available, and to the coastal zone. The first effort builds on the intellectual base provided by the observational work of Michael Bender and Daniel Sigman at Princeton, who are engaged in making cutting-edge measurements which demonstrate how both the climate and biosphere have changed in the past. Additionally, recent work by George Philander suggests the role of the tropics in abrupt climate change may have been overlooked. Philander has suggested that rapid changes in tropical temperatures may provide a mechanism for puzzling episodes in the global record involving global changes in climate on a scale of a few decades.