One Planet, One Atmosphere One Planet, One Atmosphere: timeline In their own words: Susan Solomon

UCAR at 40 Who We Are Introduction •One Planet, One Atmosphere Between Sun and Earth Measuring and Modeling When Weather Matters Most Spreading the Word Knowledge for All Looking toward the Future UCAR at a Glance List of acronyms

1960s

1964 • Model Atmosphere Akira Kasahara (pictured) and Warren Washington begin developing their first general circulation model of Earth's atmosphere. By 1981, the model incorporates forecasting as well as climate studies. Released to ressearchers as the Community Climate Model in 1983, it becomes a key tool for hundreds of university scientists. The CCM is continually updated through the 1990s (see 1996) to include higher resolution and a wider array of atmospheric processes.

1970 • Tropical Cycle Roland Madden and Paul Julian launch an analysis of winds and atmospheric pressures across the tropical Pacific. Their work soon leads to the discovery of a 40- to 50-day pulse of storminess, dubbed the Madden-Julian Oscillation, that strongly influences weather and climate across the region.

1973 • Ozone Destruction With Leroy Heidt (pictured) and others, NCAR conducts the first high- altitude balloon flight aimed at sampling stratospheric air and analyzing it for the presence of chlorofluorocarbons (CFCs) emitted from spray cans and other sources. In a landmark paper published in Nature the following year, Mario Molina and Sherwood Rowland (then both at the University of California, Irvine) suggest that CFCs break down in the stratosphere, producing a form of chlorine that could destroy life-protecting ozone. Based on this and follow-up work, the United States bans CFCs from aerosol products in 1978. In 1995, Molina and Rowland, along with Paul Crutzen (see 1979), become the first atmospheric scientists to win the Nobel Prize.

1979 • Biomass Blazes NCAR's Paul Crutzen (later at the Max Planck Institute) and colleagues publish an analysis in Nature of the atmospheric impact of biomass burning. Field programs later confirm the global extent of agricultural fires, especially in the tropics. Vast amounts of soot and gases emitted by these fires are found to affect air chemistry and radiation across huge areas.

1982–83 • El Niño The strongest El Niño to that point in the century catches scientists and the public by surprise. Weather extremes range from severe U.S. floods to drought in southern Africa and Australia. The event stimulates world governments to pay heed to the El Niño/Southern Oscillation. It also draws attention to the Tropical Ocean and Global Atmosphere research program, then just getting under way.

1983 • Acid Rain The Acid Deposition Modeling Project begins, cosponsored by NCAR and the U.S. Environmental Protection Agency. Over four years, the project, led by Julius Chang (later at the University at Albany, State University of New York), uses NCAR supercomputers to analyze acid rain and related environmental threats. Its findings feed into the decade-long National Acid Precipitation Assessment Program, which concludes in 1990 that acid rain is a serious but manageable problem.

1985 • Ozone Hole The British Antarctic Survey reports a shocking drop in springtime ozone levels above the Antarctic. Several theories emerge to explain the ozone "hole." In 1986 a paper by Susan Solomon (NOAA) and Rolando Garcia (NCAR) targets the role of polar stratospheric clouds. When these clouds are present in spring sunlight, chlorine from CFCs can deplete stratospheric ozone. The Solomon-Garcia theory is backed up by sampling in the Antarctic and Arctic. (Illustration courtesy NASA)

1988 • MLOPEX The Mauna Loa Observatory Photochemistry Experiment samples the relatively pristine air of the remote Pacific Ocean. MLOPEX and a year- long follow-up (1991–92), both coordinated by NCAR, provide the first detailed data far from continents on the seasonal cycle of the hydroxyl radical and other highly reactive chemicals. Although ozone and dust from Asia are most common over Hawaii in the spring, many reactive chemicals are found to be most prevalent during the winter months.

1992 • More Ozone Clues Research flights following the 1991 eruption of Mt. Pinatubo discover significant amounts of chlorine deposited in the atmosphere by the eruption. However, its spread is limited by global circulation patterns. In a 1992 paper, Guy Brasseur (now at the Max Planck Institute) and Claire Granier find that the chlorine released by such eruptions is unlikely to have a major impact on stratospheric ozone. Meanwhile, despite the 1987 Montreal Protocol limiting CFC production, the Antarctic ozone hole recurs throughout the decade. Lesser but still significant stratospheric depletions are observed elsewhere around the globe. (Photo by Richard Hoblitt, U.S. Geological Survey, Cascade Volcano Observatory, Vancouver, Washington)

1995 • ACE-1 Over 100 investigators from 57 institutions in ten nations gather in and near Tasmania for ACE-1, the first of the Aerosol Characterization Experiments. These field studies use NCAR aircraft and ground systems to examine the chemical, physical, and optical properties of aerosols; how aerosols form and grow; and their effect on radiation and climate. In ACE-1, led by Barry Huebert (University of Hawaii), aerosols are found to form at rates different than expected in the marine air, triggering new ideas on when, where, and how the airborne particles are formed across the globe.

1995 • NAO Along with colleagues elsewhere, James Hurrell focuses attention on the North Atlantic Oscillation. This poorly understood see-saw in North Atlantic surface pressure is found to be a major source of annual and decadal climate variations across Europe and the northwest Atlantic. In the wake of the 1997–98 El Niño, the NAO and other oceanic cycles gain further prominence.

1996 • Brewing EXPRESSO One of the most intensive studies of tropical air chemistry to date takes place in central Africa: the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO). Collaborating with French and Congolese scientists, NCAR analyzes emissions from the transition zone between Africa's rain forests and savannas, a region of frequent biomass burning. Large amounts of low-level ozone are measured and the meteorological setting turns out to be more complex than previously thought. (Photo by Lee Klinger, NCAR)

1996 • CSM Debuts NCAR releases the first version of its Climate System Model. Years in the making, the CSM (later the Community Climate System Model) provides universities with one of the most comprehensive models of the global atmosphere available. Major simulations of 20th and 21st century climate are completed before the decade is out.