CERN posted a 2009 progress report on the CLOUD project. J. Kirkby (2009) reviews developments in the CERN CLOUD project and planned tests. He describes cloud nucleation mechanisms which appear energetically favourable and depend on GCRs. On 24 August 2011, preliminary research published in the journal
Nature showed there was a connection between Cosmic Rays and aerosol nucleation. Kirkby went on to say in the definitive CERN press Release "Ion-enhancement is particularly pronounced in the cool temperatures of the mid-troposphere and above, where CLOUD has found that sulphuric acid and water vapour can nucleate without the need for additional vapours. The first CLOUD experiments showed that sulphuric acid (derived from sulphur dioxide, for which fossil fuels are the predominant source) as such has a much smaller effect than had been assumed. In 2014, CLOUD researchers presented newer experimental results showing an interaction between oxidised biogenic vapours (e.g., alpha-pinene emitted by trees) and sulphuric acid. Ions produced in the atmosphere by galactic cosmic rays enhance the formation rate of these particles significantly, provided the concentrations of sulphuric acid and oxidised organic vapours are quite low. This new process may account for seasonal variations in atmospheric aerosol particles, which are being related to higher global tree emissions in the northern hemisphere summer. CLOUD researchers note that cosmic rays have little influence on the formation of sulphuric acid–amine particle formation: "The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid–dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates." This result does not support the hypothesis that cosmic rays significantly affect climate, although a CERN press release states that neither does it "rule out a role for cosmic radiation" in climate. Dunne
et al. (2016) have presented the main outcomes of 10 years of results obtained at the CLOUD experiment performed at CERN. They have studied in detail the physico-chemical mechanisms and the
kinetics of aerosols formation. The
nucleation process of water droplets/ice micro-crystals from water vapor reproduced in the CLOUD experiment and also directly observed in the Earth atmosphere do not only involve
ions formation due to cosmic rays but also a range of complex chemical reactions with
sulfuric acid,
ammonia and organic compounds emitted in the air by human activities and by organisms living on land or in the oceans (
plankton). Although they observe that a fraction of cloud nuclei is effectively produced by ionisation due to the interaction of cosmic rays with the constituents of Earth atmosphere, this process is insufficient to attribute all of the present climate modifications to the fluctuations of the cosmic rays intensity modulated by changes in the solar activity and Earth magnetosphere. ==References==