Scientific Highlights

13 July 2017

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Gasoline cars produce more carbonaceous particulate matter than modern filter-equipped diesel cars

In contrast to nitrogen oxides, modern gasoline cars emit much more cancerogenic primary soot (black carbon + primary organic aerosol) and lead to more toxic secondary organic aerosol than modern diesel vehicles.

27 October 2016

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The substances that brighten up the clouds

Media Releases Energy and Environment Environment

Clouds consist of tiny droplets. These droplets form when water condenses around so-called aerosols – small particles in the atmosphere. To understand how in turn aerosols come into existence scientists have now created a comprehensive computer model simulation based on profound experimental data. This simulation revealed that in addition to sulphuric acid, two other substances are crucially involved in the formation of aerosols: organic compounds and ammonia. These results have now been published in the renowned journal Science.

13 October 2016


Labile peroxides in secondary organic aerosol

Aerosols, suspended fine liquid or solid particles in the air we breathe, play a central role in many environmental processes through their influence on climate, the hydrological cycle, and their adverse effects on human health. While the mechanisms by which aerosol particles affect our health remain uncertain, the atmospheric oxidation of organic vapors has been shown to be related to the formation of oxygenated organic matter with high oxidative potential, the so-called reactive oxygen species (ROS). These species may damage our lung cells through oxidative stress. Also, if we want to understand the impact of human activity on our climate, we need to be able to reconstruct the conditions before the industrial era, and to determine the main ingredients responsible for the formation of aerosols and clouds. New results obtained from the cloud chamber at CERN revealed that new aerosol particles may originate from highly oxygenated organic molecules (HOMs). They are produced upon the oxidation of natural emissions and are composed of peroxides. This class of molecules seems to have important implications for climate and health.

26 May 2016

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Present-day measurements yield insights into clouds of the past

Media Releases Energy and Environment Environment

Researchers have shown how fine particles are formed from natural substances in the atmosphere. These findings will improve our knowledge about clouds in the pre-industrial era and thus will contribute to a more accurate understanding of both the past and future evolution of our climate.

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 August 2011

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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.