Ulrike Lohmann's «Science Story» about the EU project BACCHUS

The media call her the «cloud lady». The real name for what she does is by far less poetic: Ulrike Lohmann is a Professor for Experimental Atmospheric Physics at ETH Zurich. Her research focuses on the formation and development of clouds as well as on the interaction between them and climate.

Creating a database on ice nucleating particles

As a coordinator of the collaborative EU project BACCHUS, Ulrike Lohmann has teamed up 21 partners from 13 different countries to deepen the understanding of the interaction between aerosol particles, clouds and climate. However, numerous scientific findings, publications and the development of an extensive «Ice Nucleation DataBase» are not the only outcome of the project. Some of the pleasant side effects included the opportunity to gain influence on the sustainable climate policy of the European Union, intensified relationships with the partners, project-management experience and many follow-up projects.

Aerosol particles influence the climate system These so-called aerosol particles acting as centres for ice crystals hover in our atmosphere and, despite their small size, have a major influence on the formation of clouds, their thickness and phaseas well as on the quality of the air that we breathe (particulate matter, smog). Some particles contribute to the global warming as they absorb radiation similar to greenhouse gases. Others contribute to the global cooling as they reflect parts of the sunlight back to space similar to a parasol; by this, less solar energy reaches the surface of the earth. 

No alternative to reducing CO₂ and air polluting emissions

Of course, the EU project could not conclusively answer the question raised concerning the interaction between aerosol particles, the formation of clouds and climate. The research conducted in the Arctic showed, roughly summarised, that the emissions of increased ship traffic within the area are less important for the changes in Arctic clouds than the augmented evaporation of an ocean free of ice: the latter creates thicker clouds.

According to Ulrike Lohmann, the impact of aerosol particles from human activities on ice clouds is smaller than assumed. Earlier studies had shown that clouds forming on anthropogenic particles reduced the greenhouse effect by 30 percent; the warming of the earth’s atmosphere would have been even higher without them. However, this does not mean that humanity can continue as previously done, because the pollution of the air has a strong impact on people’s health around the world. «These findings show that we have to reduce CO₂ emissions and air pollution simultaneously and even more aggressively than before. There is simply no alternative.»