National Academy of Sciences President Emeritus Ralph J. Cicerone – a leader of science and world-renowned authority on atmospheric chemistry and climate change – died at his home in New Jersey today. He was 73.

Cicerone served as the 21st president of the National Academy of Sciences from July 1, 2005 to June 30, 2016. Throughout his tenure, Cicerone was a steady voice for science in Washington, always maintaining a civilized and respectful dialogue with politicians and policymakers on some of the most challenging and controversial scientific issues of our time. At the same time, he remained a strong advocate for independent scientific advice – the hallmark of the Academy since its founding in 1863 — to inform government decision-making and public discourse.

His significant milestones and accomplishments include the restoration and renovation of the historic National Academy of Sciences building on the National Mall, the creation of a $500 million Gulf Research Program following the Deepwater Horizon disaster, two visits to NAS by President Obama, and a number of influential studies that helped to define the causes, extent, and effects of global climate change.

“The entire scientific community is mourning the sudden and untimely loss of this great leader who has been unexpectedly removed from the forefront of the scientific issues that matter most to the future well-being of society,” said Marcia McNutt, Cicerone’s successor as president of the National Academy of Sciences. “Ralph Cicerone was a model for all of us of not only doing what counts, but doing it with honesty, integrity, and deep passion.”

Cicerone was an atmospheric scientist whose research placed him at the forefront in shaping science and environmental policy, both nationally and internationally. In 2001, he led a key National Academy of Sciences study about climate change requested by President George W. Bush. Ten years later, under Cicerone’s leadership, a comprehensive set of reports titled America’s Climate Choices, which called for action on reducing greenhouse gas emissions while identifying strategies to help the nation and world adapt to a changing climate, were issued. Under Cicerone’s guidance, the NAS and the Royal Society — the science academy of the U.K. — teamed up in 2014 to produce Climate Change: Evidence and Causes, a readable publication written for policymakers, educators, and members of the public.

Engaging the general public in science was a major priority for Cicerone, who spearheaded the creation of the NAS’s Science & Entertainment Exchange. This unique program connects entertainment industry professionals in Hollywood with top scientists and engineers to assist in the portrayal of science in film and TV. He also worked on developing the widely cited 2008 book Science, Evolution and Creationism, which laid out the scientific evidence supporting evolution in a readable way for many audiences.

Helping scientists probe and understand the promise and potential problems posed by powerful emerging technologies like gene editing also was a priority for Cicerone. In 2015, he had a leading role in convening an international summit to explore the many issues raised by the arrival of a new class of genetic tools (such as CRISPR/Cas 9) for potential use in transforming humans, plants, and animals.

Within the NAS, Cicerone’s initiatives demonstrated his commitment to maintaining the institution’s relevance in a rapidly changing world — while still upholding its values of independence and excellence. Under his leadership, the NAS focused on increasing the number of women, minorities, and younger scientists elected to its membership. Cicerone also spoke out publicly for the need to maintain integrity and transparency in research. In his frequent visits and consultations with members of Congress, key Hill staffers, and federal agency heads, he spoke out on behalf of science and science education.

Prior to his election as president of the Academy, Cicerone served as chancellor of the University of California, Irvine from 1998 to 2005. He received a number of honorary degrees and many awards in recognition of his scientific work. He earned a B.S. degree in electrical engineering from the Massachusetts Institute of Technology, where he was a varsity baseball player. His M.S. and Ph.D. degrees in electrical engineering, with a minor in physics, were from the University of Illinois at Urbana-Champaign.

Cicerone is survived by his wife Carol M. Cicerone, their daughter, and two grandchildren.