The Earth, as a coupled system of atmosphere, ocean, land and cryosphere, has changed in our lifetime. The observed depletion of stratospheric ozone at high latitudes has been attributed directly to industrial use of halocarbons. Global warming is likely to result from increases in the atmospheric concentrations of greenhouse gases, such as carbon dioxide and methane, which are released by the use of fossil fuel and agricultural practices. These examples illustrate the ability of humans to alter the global environment on the time-scale of decades. Understanding the sensitivity of the Earth's climate system requires a broad base of scientific knowledge which includes detection, quantification, and prediction of the rates of change of chemical, physical and biological variables.

Our research interests focus attention on the atmosphere, ocean, cryosphere and terrestrial biosphere and on processes with the potential to change these systems over a human lifetime. An integrated approach is needed; our program requires a balance of field, laboratory and theoretical studies. Field and laboratory measurements define the rates and mechanisms of processes and exchanges within and between the atmosphere, ocean, cryosphere and terrestrial biosphere. They also provide information on the controls and feedbacks influencing these exchanges and permit identification of natural and anthropogenic processes.

Long-term observations of the Earth system, along with historical data sets and paleoclimate records, provide baseline data against which trends may be defined. The parallel development of predictive numerical models incorporating these processes is needed to interpret observations and to assess changes on regional and global scales.

The department's doctoral and post-doctoral programs are aimed at training new research scientists in the field of Earth System Science. Our goal in graduate education is to develop a comprehensive curriculum and to conduct outstanding research involving graduate students. Our doctoral-level students are expected to become researchers with a global perspective and broad research skills as well as a high level of expertise in specific areas.

The Ph.D. program in ESS features:

• An interdisciplinary curriculum covering land, ocean and atmosphere, providing an integrated approach to studying the Earth.
• Study in California, research opportunities worldwide in mountains, forests, oceans, caves, glaciers, laboratories, and climate simulation centers.
• Student research focused on global issues involving biogeochemistry, global climate, and atmospheric chemistry.
• Interactions with distinguished faculty and students, including chemists, biologists, ecologists, physicists, hydrologists, geologists, meteorologists, engineers, applied mathematicians, and oceanographers.