CliSAP successfully finished in 2018. Climate research continues in the Cluster of Excellence "CLICCS".

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Colleagues: past and present Directors at the MPI-M in January 2006: Prof. Hartmut Graßl, Prof. Guy Brasseur (current Director of the Climate Service Center Hamburg), Prof. Martin Claußen, Prof. Klaus Hasselmann and Prof. Jochem Marotzke (left to right).

CliSAP: What do you think were the findings that started modern climate science?

Graßl: It was David Keeling’s CO2 measurements taken at his weather stations at Mauna Loa on Hawaii and at the South Pole, which he set up in the International Geophysical Year, 1957. By 1960/61 it was clear that the CO2 levels on Hawaii follow a rising sawtooth pattern (natural seasonal change). It was observed that the concentration of CO2 in the air changed during the course of the year. However, at the time there were no international comparisons, and the absolute value was unreliable. Bert Bolin from Stockholm, a Swedish CO2 expert initiated “key comparisons”, whereby different labs around the world investigated the CO2 content of local air samples. It was clear that CO2 was increasing and this led to the rehabilitation of Guy Stewart Callendar’s theory of an anthropogenic greenhouse effect, which he had published in 1938 in the Quarterly Journal of the Royal Meteorological Society. The measurements also proved Svante Arrhenius’ theory dating back to 1896. 

“By the early 50s, it was possible to demonstrate with models that doubling CO2 causes warming.”

CliSAP: Nevertheless, there was still a lot of work to be done. What other factors were key in promoting climate science? 

Graßl: A commission from the Academy of Sciences in the USA! The World Meteorological Organization (WMO) was organizing the first world climate conference in Geneva in 1979, because there was a need for concrete research into whether humans affect the global climate. The basis for the investigations was the radiative transfer equation developed in the 50s. Solutions to this equation using twice the amount of CO2 showed that it would become warmer. But because there was a lack of dynamic processes, many, including Prof. Hinzpeter, were skeptical. (Editor’s note: Prof. Hans Hinzpeter, Professor at the University of Hamburg and director of MPI-M).

The turning point occurred by that conference. The US National Research Council (NRC) commission stated, “Using the best available models we estimate that an increase in CO2 concentration will cause mean global warming.” They also referred to a magnitude with error bars. A world climate programme, including the well-known WCRP (World Climate Research Programme) was agreed upon, along with three other lesser-known sections. 

CliSAP: Was it only concerned with the atmosphere at the beginning? Or were oceans involved as well? 

Graßl: From around the mid 80´s, the oceanographers were also involved. Beyond the WMO planning group in Geneva, there were project offices in particularly committed countries such as the USA, Great Britain, France and Norway. In Hamburg, we coordinated the well-known CLIVAR project for a few years, since Lennart Bengtsson at MPI-M was one of the initiators. As Director of the WCRP, I also advocated making cryosphere research global, as it is now in the Climate and the Cryosphere (CLiC) project. In the first of the WCRP projects, TOGA (Tropical Ocean Global Atmosphere), which ended in 1994, Mojib Latif was one of the founding fathers of seasonal forecasts. 

As a young researcher, I was lucky that Hans Hinzpeter, whom I had met on board the “Meteor”, gave me freedom to research and never tried to influence me. He just asked me quietly, “What’s new?” In 1973, for example, I suggested measuring the “cool skin” on open seas, as well as the radiation flux – something that was new to science back then. Creativity isn’t possible without scientific freedom. This also is true for the WCRP. A lot of money went into that programme. NASA paid several million dollars per year for modeling surface processes in the project “Global Energy and Water Cycle Experiment.” Thereby climate research turned into “big science”. In 1995, the individual funding agencies commissioned us to find out how much money was being spent on climate research. The result: around a billion dollars per year (not including satellites). However: money alone does not foster knowledge. 

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