BACCHUS is a European FP7 collaborative project under the lead of ETH Zurich, Switzerland. In the years 2013 to 2017, 21 research institutions from the European Union, Switzerland, Norway, and Israel work closely together to better understand key processes in aerosol-cloud interactions.
BACCHUS is one of three individual research projects building the research cluster "Aerosols and Climate" that the EU initiated, recognising the importantce of improving climate predications to develop sustainable policies for Europe.

The challenge

Clouds are a very important, yet not well understood feedback factor in climate change and they contribute to the effective radiative forcing (ERF) from aerosol-cloud interactions (ACI). The uncertainty of this radiative forcing is larger than for any other forcing agent (greenhouse gases, ozone, contrails, etc.). Additionally, feedbacks between the terrestrial and marine biosphere and the atmosphere involving ACI may play an important role in regulating climate change, but their relevance remains poorly quantified.

Project objectives

BACCHUS aims at quantifying key processes and feedbacks controlling ACI by combining advanced measurements of cloud and aerosol properties with state-of-the-art numerical modelling. Analysing contrasting environments is the guiding strategy for BACCHUS. We investigate the importance of biogenic versus anthropogenic emissions for ACI in regions that are key regulators of Earth's climate (Amazonian rain forest) or are regarded as tipping elements in the climate system (Arctic). We generate a unique database linking long-term observations and field campaign data of aerosol, cloud condensation and ice nuclei, and cloud microphysical properties.