Ralph J. Cicerone, born in New Castle, Pennsylvania, on 2 May 1943, was the first of his family to attend college and became a trailblazer in researching global environmental change. He died on 5 November 2016 at his home in Short Hills, New Jersey, in the company of his family.

Ralph J. Cicerone

After completing his BS in electrical engineering at MIT in 1965, Cicerone received his MS in 1967 and PhD in 1970, both from the University of Illinois at Urbana-Champaign. His thesis, on ionospheric photoelectrons, was done under Sid Bowhill.

Cicerone came of age scientifically in the 1970s, a heady but turbulent era for atmospheric science. A new class of synthetic chemicals called chlorofluorocarbons (CFCs) provided more efficient, nontoxic chemicals for refrigerants, spray-can propellants, foam blowing, and medical applications. But scientists recognized that chlorine atoms could destroy stratospheric ozone; that CFCs could deliver chlorine to the stratosphere; and that the current use of CFCs would lead to their accumulation in the atmosphere over the coming century.

The specters of global ozone depletion and predicted cancers from increased UV sunlight created a Jekyll and Hyde–like conflict with the myriad new technologies being sold under the guise of improving our daily lives. The CFC–ozone connection was the first example of a society-initiated atmospheric change that could cause global environmental damage. The resulting contentious interactions of Cicerone and the other early scientific explorers with the chemical industry has been dubbed the ozone wars.

One of the hardest ideas to get across to the public and policymakers was how CFCs would reach the stratosphere, build up chlorine atoms, and destroy the ozone layer. Cicerone and others who recognized the CFC problem—including Paul Crutzen, Chuck Kolb, Michael McElroy, Mario Molina, Sherry Rowland, Steve Wofsy, and one of us (Stolarski, then his colleague at the University of Michigan)—led the charge; they communicated not merely through scientific journals but also directly to the public. Cicerone pushed the science from the local to the national level, and he was responsible for the 1974 Ann Arbor City Council ban on CFC use in spray cans. That was followed by other local bans on CFCs, proposed amendments to the US Clean Air Act in 1977, and eventually the US and Nordic bans on such spray cans.

The ozone wars were long and brutal, but they were finally resolved by international scientific ozone assessments, detection of the Antarctic ozone hole and ozone depletion globally, and the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer. The scientific accomplishments of those early explorers were recognized with the awarding of the 1995 Nobel Prize in Chemistry to Crutzen, Molina, and Rowland.

Cicerone’s career shows lessons learned from the ozone wars: Scientific integrity is tantamount, facts must not be subjugated to political favor, collegiality among scientists is key, and global environmental and societal change is the story of the coming century.

Cicerone is best known in the scientific community for his leadership in ushering in the modern era of atmospheric chemistry and biogeochemical cycles of the Earth system and for coupling that knowledge to societal effects of ozone depletion and climate change. His research led to new ways of understanding global atmospheric changes and identifying the causal chain that implicated humans. When most scientists involved in atmospheric chemistry were not interested in the biosphere, Cicerone studied methane and the complex systems that produce it, consume it, and sometimes release it to the atmosphere. His investigation of methane emissions from rice paddies was one of the first biogeochemical research projects; he studied the natural biogeochemistry of a human-made compound to better understand its environmental threat. The new information was critical for assessing the damage to the ozone and climate from agricultural chemicals and influenced the national debate on regulating them.

Beyond his scientific accomplishments, Cicerone was unique in organizing and energizing scientists. As director of the atmospheric chemistry division at the National Center for Atmospheric Research in 1981–89, he influenced a generation of scientists. In 1990, working with Rowland at the University of California, Irvine, he founded the new Earth system science (ESS) department—the first at a university to focus primarily on global change. Cicerone became Irvine’s dean of physical sciences in 1994 and chancellor in 1998. Throughout his career, he maintained the perspective that the best science is accomplished by the best scientists working together as a community.

In 2005 Cicerone was elected president of the National Academy of Sciences (NAS), from which he just retired this past summer. As NAS president, he emphasized objective scientific studies in support of public policy. Among them are ones on climate change impacts, past temperature reconstructions, active remote sensing, and solar observations. In the face of an administration and Congress that doubted climate change, Cicerone used NAS funds to organize an independent review of the Intergovernmental Panel on Climate Change’s 2001 assessment; it affirmed the IPCC’s findings. When the IPCC became involved in another major controversy, Cicerone organized the international group of national science academies, and the resulting review helped save the international climate assessments and maintain the pressure to act on climate change.

Cicerone’s natural leadership was evident in the scientific problems he pursued or convinced others to pursue. Recognizing societal aspects was a hallmark of his work. His intellect, insight, kindness, and collegiality made him a pleasure to work with. Cicerone’s vision of biogeochemistry and global change has altered graduate education internationally and influenced the way many of us approach global-change research. We will miss his regular questions and curiosity about the planet.