In his darkest hour, Ben Santer considered walking away from his life's work. A physicist and atmospheric scientist at the Lawrence Livermore National Laboratory in California, Santer has spent his career detailing the modeled and observed effects of human-induced climate change. His research led to his appointment as the lead author of a key section of the 1995 Intergovernmental Panel on Climate Change assessment report, which concluded, "The balance of evidence suggests a discernible human influence on global climate."
The statement was one of the first, definitively worded assertions from the scientific community recognizing people's role in triggering climate change, and it drew outrage from skeptics and deniers. The critics didn't limit their vengeance to Santer's scientific findings, and accused him of personally manipulating and deleting sections of the report.
"I was very disheartened by what was happening and the highly personal nature of some of the attacks," Santer recalls. "After the assessment report was published and the 'balance of evidence' statement came out, I seriously considered giving up science."
Santer stuck it out, in large part due to the words and encouragement of Stephen Schneider, a colleague from Stanford University and a titan in the field of climate science. Schneider spent his career studying human effects on the planet and climate, and the consequences to different courses of action — and inaction. He also helped craft the "balance of evidence" statement — and had weathered his share of denigration and even death threats over the years. He refused to allow Santer to walk away from his research and conclusions.
"Steve was a huge source of support to me," Santer says. "He told me, 'Ben, some things are worth fighting for, and this is worth fighting for.'"
Schneider, who died in July 2010, is looked upon as a pioneering mind and voice within the climate science community. Throughout his career, Schneider's research paralleled the exploration of global warming trends in the 1970s and the increasing sense of urgency to address the risks caused by man-made greenhouse-gas emissions.
From his days as a postdoctoral NASA fellow in the early 1970s, Schneider was responsible for some of the first studies and models of the impacts of greenhouse gases on climate. During two-plus decades at the National Center for Atmospheric Research in Boulder, Colorado, Schneider tackled a range of subjects: modeling the climate effects of a nuclear winter, unraveling the feedback relations between environmental parameters, and contemplating the prospects of geo-engineering strategies to offset warming.
Schneider moved to Stanford in 1996, where he was a professor of interdisciplinary environmental studies and a senior fellow at the school's Woods Institute for the Environment. He contributed to all four IPCC reports-a fifth is being drafted now-and served as the maestro when it came to communicating and framing climate research and policy implications.
A three-day symposium in Schneider's name took place at the National Center for Atmospheric Research the last week of August. With topics drawn directly from Schneider's bookshelves, the conference attracted more than 150 friends, colleagues and researchers to remember Schneider's contributions and to share their own research across a number of disciplines.
Among his legacies, Schneider championed an interdisciplinary research agenda, drawing on the physical and social sciences in studying climate change. A rising tide of interdisciplinary academic and research programs that extend across traditional concentrations is one of his lasting imprints. A forthcoming plan of the U.S. Global Change Research Program, to be announced in September, will recommend expanding the program's scope along interdisciplinary lines. The development would "warm Steve's heart," says Warren Washington, a veteran atmospheric scientist at National Center for Atmospheric Research who first met Schneider in 1972.
"Over the years, he pushed for more interdisciplinary science, and previously, the U.S. Global Change Program was primarily focused on climate change," Washington says. "What's happening now is the program is being brought to its original congressional mandate [from 1990]. The driving force is still humankind's effect on the planet, but there's a whole host of issues that will be looked at in an integrated way, such as health, agriculture, population, and urbanization."
Some researchers are also following up on another of Schneider's enduring interests in discussing the "tails of distribution" — the low-probability, high-consequence outcomes of climate change, such as a megadrought.
"Steve, rightly so, said the policymakers need to know what's in the tails because it actually makes a big difference to the issue of policy," says Terry Root, a Stanford biologist and Schneider's wife.
Schneider believed that despite scientific uncertainty, the research and trends behind climate change — including potentially extreme yet less likely events — needed to be bluntly stated to the public and policymakers, and to be defended against critics who claim that unknown aspects are reasons to delay adaptation or mitigation measures.
A May 2011 report from the National Research Council, "America's Climate Choices," carries Schneider's message. The report's findings state that uncertainties exist in projecting future greenhouse gas emissions and the severity of climate change impacts, but the council concludes: "Uncertainty is not a reason for inaction, however; it is, in fact, a compelling reason for action, especially given the possibilities of abrupt, unanticipated, and severe impacts."
Symposium speakers also credited Schneider for pushing his colleagues and former students to recognize that being a climate scientist doesn't mean abstaining from sharing one's views as an informed citizen with personal values. Long before most people even knew about global warming, Schneider led the charge, writing books on the subject and even appearing four times on "The Tonight Show" with Johnny Carson.
"When he started doing this in the 1970s and went on Johnny Carson, he got a hell of a lot of flak. It was seen as a negative," Root says. "He got a lot of static for what he did, but obviously he persisted, and now it isn't a negative to talk to reporters. He was the person who really made it safe for scientists to talk to the media and policymakers."
Scientists, in general, are often assumed to be uncomfortable discussing the policy implications of their results, let alone the riskiest and severest effects. No doubt, one of Schneider's most lasting impacts is the example he set for colleagues and future climate scientists-being comfortable and resolute in asking the tough questions, and providing the even tougher answers about climate change.
"The big questions Steve posed and helped clarify remain today," says Michael Mann, director of the Earth System Science Center at Penn State University.
Mann has also endured attacks on his reputation and work, which includes the notorious "hockey stick graph" that illustrates the unprecedented spike in global temperatures during the last decade and century compared with the previous millennium. In 2009, he was one of the targets of the so-called Climategate controversy, when hackers nabbed thousands of scientists' emails and claimed to have found evidence of shady practices by Mann and others.
"During the toughest times, when I was being attacked, I looked to Steve as a leading light, and I went to him for advice," says Mann, who has been cleared of any misconduct by several review panels, including an inquiry by the National Science Foundation concluded in late August.
Mann is working with colleagues, looking at how major atmospheric events, such as the Asian summer monsoon, will be influenced by projected changes. He's among several researchers developing the next generation of climate models to refine estimates and reduce uncertainties by incorporating paleoclimate data-records of long-past environmental conditions-into their assessments. And, in the spirit of Schneider's work and vision, Mann gives lectures, communicating the science to the public.
"One of his most significant contributions to the public discourse," Mann says of Schneider, "was this notion of the 'double ethical bind'-the idea that ultimately, it's possible to be faithful and honest to the science, and to be effective as a communicator. You don't have to sacrifice one for the other."