Stephen Schneider, 65, died today of a heart attack as his flight to London from a science meeting in Sweden was landing—a sad but fitting end for a busy climate scientist who rarely sat still. An indefatigable advocate of the truth in climate science with all its uncertainties made plain, Schneider had been globetrotting for almost 40 years in his campaign to save the planet. The world had made progress toward that goal, he recently told Science, but climate's fate is now at the mercy of random events.
In his recent book, Science as a Contact Sport: Inside the Battle to Save Earth's Climate , Schneider—a professor at Stanford University—tells of his journey from studying plasma physics in graduate school, doing climate science in the 1970s and 1980s, and adding climate science assessment for policymakers in the 1990s and 2000s. His most concrete achievement in climate assessment may have been getting his colleagues on the Intergovernmental Panel on Climate Change to explain  how certain they actually were about the science, what they really meant by terms running from "exceptionally unlikely" through "likely" to "virtually certain."
While energetically exposing climate's complexities and inevitable uncertainties, he for many years assumed the Carl Sagan role in the climate community—stunningly articulate explainer of the science and its defender against any and all skeptics of its core truths. "I am an activist," he told  The New Republic last November. "I want the world to be a better place. ... What to do about what we know—that's a question of values. But it's values informed by science."
Despite all of his efforts that had helped bring decision-makers to the verge of reining in global warming, Schneider saw the final push that would tip the world—and the United States in particular—toward action as being out of his or anyone else's hands. On a cell phone from a plane about to leave the gate last May, he told Science that it isn't more reports from august scientific bodies that will eventually save the day. Rather, it will be random events such as the oil spill in the Gulf of Mexico or the next super heat wave. But that realization apparently hadn't yet slowed him down.
(See a ScienceInsider forum  in which Schneider participated and one of his final videotaped interviews , in which he discussed a controversial paper  on climate skeptics he had recently published in the Proceedings of the National Academy of Sciences .)
*This item has been corrected. The original version stated incorrectly that Scheider was flying from a meeting in Stockholm; he flew from Gothenburg after attending a meeting in Karingon.