Physicist, meteorologist, grammar school teacher and weather prophet – Hans Ulrich Dütsch was a man who was interested and involved in many things. This versatility induced Huw C. Davies, Head of the ETH Department of Environmental Sciences (1), to praise this "universal scholar" in his address at the funeral service for the atmospheric physicist.

Superb interpreter of data

Is it possible in a biography like that of Hans Ulrich Dütsch to select one outstanding aspect? Johannes Stähelin, ETH professor at the Institute for Atmospheric and Climate Sciences, considers the question before answering, "One of Dütsch's most decisive contributions was his scrupulous attention to measurements and interpretation that enabled a more accurate assessment of the level of the anthropogenic destruction of the ozone layer.“ Already in his PhD thesis in 1946, Dütsch showed that the theory of chemical generation of ozone, formulated by Sidney Chapman in 1930, was not adequate to explain the annual fluctuations in the ozone concentration of the stratosphere, i.e., 10 to 50 kilometres above the Earth's surface. From his results Dütsch predicted flows of air in the stratosphere. Later these transports of air were identified and came to be known as Brewer Dobson Circulation.

Interest from the US Air Force and Flavio Cotti

"But this revolutionary work would not have been possible without Dütsch's supervisor, F. W. Paul Götz," adds Stähelin. Because it was Götz who had started to measure ozone levels, as far back as 1926, in Arosa. The station was also a concern near to Dütsch's heart. When Götz died in 1954 the future of the light-climatic observatory in the alpine health resort was imperilled. In his capacity as an NZZ reporter, Dütsch met Harry Wexler, who was the research director of the US weather bureau at the time, at a conference. Wexler encouraged Dütsch to submit a project that would ensure the survival of the station to the US Air Force. The Americans were keen to collect observations from all over the world on Earth's atmospheric phenomena in order to develop their radar system. The first funds flowed from the States to Arosa in 1956. On the directive of the Federal Council, however, they were returned because they were deemed to run contrary to the principle of Swiss neutrality. Eventually, funding was assured by ETH and the Swiss National Science Foundation (SNF) – but in the process two years of measurements were lost.

The future of the station in the Grison was threatened anew after Dütsch's retirement. Initially, nobody wanted to fund the station. It wasn't until Dütsch wrote to the then Federal Councillor, Flavio Cotti, that funding for the station in Arosa was agreed. From this time on the station became part of MeteoSchweiz and today its scientific and technical upkeep is ensured by Johannes Stähelin and his team.

In the front line

The fact that Arosa had the longest series of ozone measurements anywhere in the world was not the only deciding factor in Dütsch's subject for his PhD thesis; it was also important to identify problems of ozone destruction in the stratosphere. And Stähelin goes on to say that the young Swiss atmospheric physicist was one of the first to recognise the importance of the works of the (later) Nobel Prize winner Paul J. Crutzen along with those of Mario Molina and Sherwood Rowland. It was Crutzen's explanation of the catalytic process of ozone depletion by nitrogen in the stratosphere in the early 1970s that initiated wide discussion of the danger to the ozone shield by supersonic jets. Dütsch was approached by the Americans for his expertise when they wanted to build up a new fleet of planes. Stähelin points out that this was the first public debate where environmental questions played an important role. In the end, the Americans renounced their plans for supersonic jets.

Researched ozone in the atmosphere: ETH Professor Hans Ulrich Dütsch, who died recently.

"Dütsch was always aware of environmental problems," says Stähelin, but he avoided panic-mongering. Dütsch understood his role as the provider of a wide scientific basis with which to measure air pollution. Apart from stratospheric ozone, he also turned his attention to surface ozone, something that poses a direct danger to human beings, when this issue was debated in Switzerland, shortly before his retirement.

Carrying on Dütsch's work

How far are Dütsch's investigations being continued today? Stähelin says that a doctorate student has just finished a study based on measurements from the station in Arosa, in which he examined the influence of the Montreal Protocol, signed in 1987. Apart from the surveillance for this international agreement to protect the ozone layer, Stähelin's team is working increasingly on the interdependency of ozone and the climate. The atmospheric chemist points out that ozone in the troposphere, i.e. at levels of up to 10 kilometres, is a strong greenhouse gas. According to the IPCC (the International Panel of Climate Change), since pre-industrial times the effect of this gas is a quarter of that of CO² – and therefore anything but negligable. Doesn't this call for immediate action? Stähelin, like Dütsch thinks he can improve matters most by producing a sound scientific basis for decisions – implementation is up to the politicians.

Unusual biography for a scientist

This doesn't mean that knowledge produced at universities should not be made available to the public. Stähelin considers that Dütsch did a lot towards a general understanding of meteorology with his NZZ contributions. His experience as a grammar school teacher probably helped him here. Indeed, 16 years after obtaining his PhD Dütsch was teaching at the Kantonsschule in Zurich – an unusual career path for a scientist if one looks around today. Even though Stähelin doesn't want to stand in the way of modern developments, he finds it regrettable that so much weight is now given to an absolutely linear academic career. At any rate, The atmospheric chemist is grateful to have had the chance to know the modest, sometimes almost introverted, but kind person who was Hans Ulrich Dütsch – a human being with atmosphere.