Scientific Highlights

29. June 2015

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Particulate matter from modern gasoline engines damages our lungs

Media Releases Environment Energy and Environment

For years, studies have proved that fine dust from petrol engines can damage our health. Modern engine technology does not help, either, as researchers from the University of Bern and the Paul Scherrer Institute (PSI) reveal.

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17. September 2014


Airpocalypse explained

Media Releases Environment Energy and Environment

The causes of China's record level fine particulate pollution in winter 2013
At the beginning of 2013 a greyish-brown blanket of smog lay over large areas of China for several months. The fine particle pollution was higher by 1 to 2 orders of magnitude than the levels normally measured in Western Europe and the United States. An international team of researchers under the lead of the Paul Scherrer Institute PSI and the Institute of Earth Environment, Chinese Academy of the Sciences revealed the causes of the airpocalypse. The study published in the journal Nature also describes what steps are to be taken to prevent an environmental crisis of this kind in the future. See also the news report of the Chinese TV (in Chinese) on 2014-09-18:

13. May 2014


Unassuming rampant polluters on two wheels

Media Releases Energy and Environment Environment

In some towns small mopeds cause more air pollution than cars

Not cars or trucks, but mopeds with their two-stroke engines are the main source of fine particles and other air contaminants in many towns in Asia, Africa and southern Europe. This is revealed by the study of an international research team headed up by researchers at the Paul Scherrer Institute PSI. The reasons for the high emissions are the combustion properties in two-stroke engines and the overly lenient emission requirements for small two-wheelers. The study findings are to be published on 13 May 2014 in the journal Nature Communications. News report on Swiss TV (in German)

17. December 2013


Experiments in the clouds – how soot influences the climate

Media Releases Energy and Environment Environment

PSI-researcher Martin Gysel receives prestigious European funding (ERC Consolidator Grant) for his studies on the role of soot in cloud formation and global warming.

6. October 2013


Particle formation in the atmosphere – further aspect unveiled via the CLOUD experiment at CERN

Media Releases Energy and Environment Environment

Clouds consist of cloud droplets that are formed from tiny particles floating in the atmosphere. How these particles develop, however, largely remains a mystery. The formation of particles from amines and sulphuric acid has now been described for the first time – a milestone in atmospheric research.

19. April 2010

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The mass concentration of volcanic ash from Iceland in European airspace

Media Releases Energy and Environment Environment

Data of the Paul Scherrer Institute from the High-Alpine Research Station Jungfraujoch yield important information.
The eruption of the volcano Eyjafjallajokull in Iceland has stalled flight traffic in large parts of Europe. Decision makers had to base their decisions mainly on model calculations for the volcanic plume dispersion. How dangerous is this volcanic ash layer for planes?

18. January 2010

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News from the smog chamber: mechanisms of particle formation in the atmosphere unveiledt

Media Releases Environment Energy and Environment

Up to the present time, the nucleation or new formation of particles in the atmosphere has been a great enigma. Until recently, research was based on the assumption that sulphuric acid played the central role in particle formation. However, laboratory experiments and field tests have consistently provided conflicting results. In the lab, considerably higher concentrations of sulphuric acid are required for nucleation to take place than in the atmosphere itself. Now scientists from the Paul Scherrer Institute (PSI) have found out the cause for these conflicting results from their smog chamber. These findings will advance climate research to a significant degree.

10. December 2009

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Mystery solved: how fine particulates are formed in the air

Media Releases Environment Energy and Environment

Researchers from the Paul Scherrer Institute, the University of Colorado and 29 other research institutions in various countries have investigated the composition of the organic constituents of the fine particulates found in various regions of the world, and have identified the original substances from which they are formed in each case. For the first time ever, this has enabled them to explain the role played by the individual components of emissions in the development of fine particulates.

25 Aug 2011

CCN formation mechanism in lower troposphere needs revision

Atmospheric aerosols exert an important influence on climate1 through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H2SO4–H2O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.
Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation
Kirkby et al.,
Nature, 25.8.2011,
DOI: 10.1038/nature10343

Contact: Prof. Dr. Urs Baltensperger, Telephone: +41 56 310 24 08, Email:,

Media Release: Klimaforschung am Teilchenbeschleuniger: Beschreibung der Aerosolneubildung muss revidiert werden (in German only)