This has been another year of major accomplishment for the Climate and Global Dynamics Division (CGD). CGD scientists have completed a 300-year control run using the first version of the Climate System Model (CSM) and made the data available to the community. CGD scientists have also completed a 125-year run in which carbon dioxide was prescribed to increase at 1% per year. The monthly averaged data from that run is also available to the community. Nearly 20 papers describing the CSM and its simulation characteristics have been submitted to the Journal of Climate, and they will hopefully appear in the April or May, 1998, issue.
In the last year, a Scientific Steering Committee has been appointed to guide the development and use of CSM. Eight working groups have been formed with foci ranging from model development for the next version of CSM to diagnostic studies using the present model and datasets. CGD sponsored the second annual CSM Workshop in June, 1997, in Breckenridge, Colorado. This workshop was attended by approximately 150 scientists, and the level of non-NCAR participation has grown substantially. The CSM is rapidly becoming an important, widely-recognized community resource for climate studies.
CGD also developed a Strategic Plan that will be used to focus our research over the next 3 to 5 years. There are 6 major elements, each of which has modeling and diagnostic parts. Most involve people from more than one section within CGD, scientists from other divisions, and collaboration with scientists outside of NCAR.
The first of these projects is Climate of the 20th Century and Future Climate. We are developing the best estimates for concentrations of carbon dioxide, other greenhouse gases, and sulfate aerosols beginning in the late 19th century up to the present. These will be used to change the atmospheric forcing in the CSM in an experiment that will examine how well the model can simulate the climate of this century. We will then continue these runs using plausible scenarios for the evolution of greenhouse gases for the 21st century to see the range of global warming outcomes that CSM predicts.
Scientists in CGD and the Atmospheric Chemistry Division (ACD), as well as scientists outside of NCAR, will collaborate on a variety of projects to incorporate chemistry and biogeochemistry into the atmosphere, ocean, and land surface components of CSM. We will expand the capability of the CSM to examine the carbon cycle, the nitrogen cycle, the sulfur cycle, stratospheric and tropospheric ozone, and aerosols. CSM will evolve towards a coupled Earth System Model (ESM).
The study of past climates is also of great interest to CGD scientists, both for its own sake and to test the CSM in climate regimes relatively far from that of the present. If the CSM can in fact simulate some of the previous climates, which are due to different climate forcings than the present, the credibility of the model simulations for the present and the future will be enhanced. We have developed a special lower resolution version of the CSM that will be made available to the paleoclimate community for these investigations. Work has begun on understanding the climate of the past 21,000 years. Attention will be focused on the Last Glacial Maximum (21,000 years ago) and the Climatic Optimum (6000 years ago), as well as the past few centuries.
Two special studies will focus on Variability and Predictability in the North Atlantic and Arctic Regions and Variability of the Tropical Oceans and Global Atmosphere. The North Atlantic/Arctic system is thought to be the source of much of the interdecadal variability of climate. The tropical oceans, especially the Pacific, are involved in seasonal-to-interannual variability, including the El Niño Southern Oscillation (ENSO). Both of these projects will include modeling and diagnostic studies and involve atmospheric scientists and oceanographers plus, for the Arctic, studies of the interactions of sea ice with the other two media. These projects will be looking for mechanisms for variability and how these mechanisms depend on the state of the climate. One important question to be examined is whether the presently observed climate variability will change if the mean climate changes due to global warming or other influences.
CGD has a long history of studies of global dynamics with application to dynamical prediction. The beginning of the U.S. Weather Research Program (USWRP) has given CGD the opportunity to refresh its activities in this area. CGD plans to carry out experiments to relate the (theoretical) predictability of weather events to the uncertainty of prediction of the events, to develop a better understanding of weather and climate regimes and to develop methods to predict transitions between regimes, and to investigate the influence of various boundary forcings, such as sea-surface temperature, land-surface moisture, and others, on the predictability of weather extremes, particularly over North America.
I expect the solid accomplishment of the last year to continue as CGD scientists work on the projects outlined above. These projects will enhance our knowledge of phenomena that impact the lives of all of us, such as global warming and ENSO. The time seems right for substantial progress.