Obituary;Steve Schneider;

Stephen Schneider, climate scientist, died on July 19th, aged 65.

“Mark twain had it backwards,” Steve Schneider joked, in a lecture he gave to the American Association for the Advancement of Science (AAAS) in 1972. “Nowadays, everyone is doing something about the weather, but nobody is talking about it.” The lecture was on the topic that Mr Schneider, then 27, had been working on for two years and would work on for another 38: what were humans doing to the climate?

The 1960s had brought a new way of talking about the weather—a way of representing it in punched cards that could be fed into a computer. These models, limited though they were, let their creators ask questions no simply tabulated data could answer, and see processes that the details of the real world obscured.

As a young physical scientist on the lookout for a new field that posed big questions, a former student politician who wanted to make a difference to the world and an inveterate show-off susceptible to the charms of a high profile, these models offered Mr Schneider what he needed. But in giving him a way to play with the world and its processes they gave him something he loved, too.

As a boy growing up on Long Island he had greeted news of hurricanes by going up to the attic to sit with an anemometer, and built his own telescope in order to gasp at the planets it revealed. When computer models gave him the power to spin up winds on planets of the mind, his first big topic was a study of the net effects of smoggy pollutants in the atmosphere, which cool the planet down, and the carbon dioxide which warms it up. Other work focused on the warming and cooling effects of clouds and the climate's sensitivity to greenhouse gases.

Public interest in his work outstripped its acceptance by the academic meteorologists Mr Schneider was working with at the beginning of his career. They found computer modelling of the climate suspicious enough in itself, and Mr Schneider's insistence that it should lead to interdisciplinary interactions with biologists interested in ecosystems—and even social scientists interested in human responses—made things worse. When he returned to his office after the AAAS talk, he found a New York Times article that quoted his Twain gag pinned up on a noticeboard with “Bullshit” stamped across it. His subsequent appearances on “The Tonight Show with Johnny Carson” probably did little to improve his reputation with conservative colleagues. Nor did his fairly rapid dismissal of his early belief that cooling caused by pollution might outstrip warming due to carbon dioxide. In later years, when he and his colleagues had pushed climate change, and in particular greenhouse warming, on to the agenda, people keen to ensure a lack of action made much of his about-face over cooling, preferring to accuse him of modish inconsistency than to see him as someone who had worked to improve his models, and as a result had changed his mind.

Mr Schneider's high profile as a proponent of action on climate change—he was the editor of an important journal, Climatic Change, and an influential member of the Intergovernmental Panel on Climate Change (IPCC) more or less from its inception—would have made him a favourite target for such antagonists anyway, but he came in for particular scorn because of his willingness to discuss the inevitable tensions between advocacy and academic integrity. Critics of Mr Schneider, including this newspaper, portrayed him as giving in to this tension, and being willing to tell “necessary lies” when it suited his purposes. He countered such attacks vehemently, saying such a conclusion rested on a slanted reading of what he had said on the subject. He had no time for advocacy without truth.

Far from being a voice of orthodoxy, Mr Schneider encouraged debate, and doubts, on subjects that some of his colleagues thought beyond the pale. He convened meetings on the Gaia hypothesis and its notion of a self-regulating Earth; he provided space for discussions of geoengineering schemes for cooling the planet. When his friend Carl Sagan (who had recommended him to Johnny Carson) led the charge on the climatic effects of nuclear war as a case for disarmament, Mr Schneider, whose politics were close to Sagan's, damaged their friendship by saying publicly that the models he worked with were considerably less prone than Sagan's to the creation of “nuclear winters”.

At the IPCC, Mr Schneider's deepest commitment was to candour about uncertainties and the role played by subjective expert judgment. He loved models for the patterns and ideas they revealed much more than he trusted them as detailed guides to action. He was more likely to criticise a piece of science for underestimating its own level of uncertainty than for coming to a conclusion he disagreed with.

In his mid-50s he found his ideas about how to make weighty decisions in uncertainty tested in a more personal way. He was diagnosed with a rare lymphoma. With his wife as advocate and his doctor as expert, he tried to understand the processes involved and decide on actions accordingly. His choice of aggressive treatments helped him survive until a heart attack claimed him on an aircraft ferrying him from one climate meeting to the next.