Saturday, May 28, 2011

New Study Links Cosmic Rays To Aerosols/Cloud Formation Via Solar Magnetic Activity Modulation

Following my recent theme on Cosmic Rays and Cloud formation is this recent peer reviewed study covered via Watts Up With That:

New study links cosmic rays to aerosols/cloud formation via solar magnetic activity modulation

Scientists at Aarhus University (AU) and the National Space Institute (DTU Space) show that particles from space create cloud cover

New input to the United Nations climate model: Ulrik Ingerslev Uggerhøj, Physics and Astronomy, AU, along with others including Jens Olaf Pepke Pedersen and Martin Bødker Enghoff, DTU Space, have directly demonstrated in a new experiment that cosmic radiation can create small floating particles – so-called aerosols – in the atmosphere. By doing so, they substantiate the connection between the Sun’s magnetic activity and the Earth’s climate.

With the new results just published in the recognised journal Geophysical Research Letters, scientists have succeeded for the first time in directly observing that the electrically charged particles coming from space and hitting the atmosphere at high speed contribute to creating the aerosols that are the prerequisites for cloud formation.

Clouds, which are drops of water, occur more easily when water vapour in the atmosphere can condense around particles – dust or large clusters of molecules. Researchers have now shown that electrons caused by cosmic radiation can create small particles that can grow in the atmosphere into such cloud condensation nuclei. This is interesting in the light of the controversial theory proposed by Henrik Svensmark, DTU Space, who postulates a correlation between solar activity and the Earth’s temperature: when the Sun’s activity increases – and thereby magnetic fields (seen as more sunspots) – more of the cosmic particles deflect and fewer therefore reach the Earth’s atmosphere, whereupon there is less cloud formation and the temperature rises on the Earth’s surface. And conversely: when the magnetic field is weakened, the temperature drops. (Graphics: DTU Space)

The more cloud cover occurring around the world, the lower the global temperature – and vice versa when there are fewer clouds. The number of particles from space vary from year to year – partly controlled by solar activity. An understanding of the impact of cosmic particles – consisting of electrons, protons and other charged particles – on cloud formation and thereby the number of clouds, is therefore very important as regards climate models.

With the researchers’ new knowledge, it is now clear that here is a correlation between the Sun’s varying activity and the formation of aerosols in the Earth’s atmosphere. Initially, the researchers have demonstrated that there is a correlation, and they will therefore now carry out systematic measurements and modellings to determine how important it is to the climate. The new studies will be made at DTU Space in Copenhagen, with support that includes a new grant of DKK 2 million (approximately EUR 270,000) from the Danish National Research Councils.

Experiment in a climate chamber

Section of ASTRID – Denmark’s largest particle accelerator – at Aarhus University, from which scientists have sent electrons into a climate chamber and created conditions similar to the atmosphere at the height where clouds are formed. Simply by comparing situations in the climate chamber with and without electron radiation, researchers can directly see that increased radiation leads to more aerosols. These aerosols are interesting because they can make water vapour in the atmosphere condense into drops of water – i.e. clouds. (Photo: AU)

In a climate chamber at Aarhus University, scientists have created conditions similar to the atmosphere at the height where low clouds are formed. By irradiating this artificial atmosphere with fast electrons from ASTRID – Denmark’s largest particle accelerator – they have also created conditions that resemble natural ones on this point.
Simply by comparing situations in the climate chamber with and without electron radiation, the researchers can directly see that increased radiation leads to more aerosols.
In the atmosphere, these aerosols grow into actual cloud nuclei in the course of hours or days, and water vapour concentrates on these, thus forming the small droplets the clouds consist of.


Based on the correlation between the level of activity of the Sun and the global temperature of the Earth, the Danish climate researcher Henrik Svensmark proposed a controversial theory in the late 1990s: that there could be a correlation between the intensity of the cosmic radiation that hits the Earth – and which is affected by the activity of the Sun – and the number of clouds formed.
With the experiment in Aarhus, the research group has now taken one step closer to being able to demonstrate this relationship. There is much to indicate that climate models must hereby take cosmic radiation into consideration. In doing so, the new results provide hope for better climate models that can describe the Earth’s temperature and climate more accurately.

Comments from three of the scientists behind the experiment:

Senior Scientist Jens Olaf Pepke Pedersen, DTU Space, says:

“Aarhus University has outstanding facilities that enable us for the first time to carry out a very direct test of the theory on cosmic particles causing droplet formation in the atmosphere.”

Scientist Martin Bødker Enghoff, DTU Space, adds:

“Before we can say how great the effect is, it’s clear that our results must be verified – just as more measurements and model computations need to be made. However, we can already reveal with no doubt whatsoever that there is an effect.”

“It’s a pleasure to see these results in climate research being achieved at our accelerator. Actually, it’s only possible to do corresponding research at CERN – the joint European research centre,” says Associate Professor Ulrik Uggerhøj, Department of Physics and Astronomy, Aarhus University.

Facts about the experiment

A chamber contains air with precisely balanced amounts of sulphur dioxide, ozone and water vapour irradiated with electrons. Sunlight is a necessary ingredient for aerosol formation in the natural atmosphere, and it is imitated in the climate chamber by a lamp that emits ultraviolet light. Natural atmospheric processes such as the formation of sulphuric acid are thus imitated, and these are an important ingredient in the aerosols. When electrons from the accelerator irradiate the air mixture, an increase takes place in the production of aerosols, which act as nuclei for the production of cloud droplets. In previous SKY experiments conducted by DTU Space in Copenhagen, cosmic radiation was simulated by gamma radiation, and the scientists saw here that the gamma rays could also form aerosols. In the new experiment with the energy-rich electrons from the ASTRID accelerator, there is much more resemblance to the cosmic rays that occur in nature.

Competitors hot on their heels

A major international research group at the European Particle Research Centre (CERN) in Geneva, Switzerland, has worked for several years on demonstrating the correlation that the Danish researchers have found, and the group has announced that its members are also on the way with their first extensive results. Compared with the CERN project, the Danish scientists have an extremely modest budget, but when it comes to producing particles resembling cosmic ones, the facilities at Aarhus University are equal to the most advanced facilities in the world.

Associate Professor Ulrik Ingerslev Uggerhøj goes into more detail in the video interview below (in Danish only)

Here’s the abstract


Aerosol nucleation induced by a high energy particle beam

Key Points
  • Cosmic rays increase nucleation rate
  • A particle beam is not needed for experiments
  • Ions are important for atmospheric nucleation rate

Martin B. Enghoff

National Space Institute, Technical University of Denmark, Copenhagen, Denmark

Jens Olaf Pepke Pedersen

National Space Institute, Technical University of Denmark, Copenhagen, Denmark

Ulrik I. Uggerhøj

Department of Physics and Astronomy, University of Aarhus, Aarhus, Denmark

Sean M. Paling

Department of Physics and Astronomy, University of Sheffield, Sheffield, UK

Henrik Svensmark

National Space Institute, Technical University of Denmark, Copenhagen, Denmark

We have studied sulfuric acid aerosol nucleation in an atmospheric pressure reaction chamber using a 580 MeV electron beam to ionize the volume of the reaction chamber. We find a clear contribution from ion-induced nucleation and consider this to be the first unambiguous observation of the ion-effect on aerosol nucleation using a particle beam under conditions that resemble the Earth’s atmosphere. By comparison with ionization using a gamma source we further show that the nature of the ionizing particles is not important for the ion-induced component of the nucleation. This implies that inexpensive ionization sources – as opposed to expensive accelerator beams – can be used for investigations of ion-induced nucleation.

Received 8 February 2011; accepted 31 March 2011; published 12 May 2011.

Citation: Enghoff, M. B., J. O. P. Pedersen, U. I. Uggerhøj, S. M. Paling, and H. Svensmark (2011), Aerosol nucleation induced by a high energy particle beam, Geophys. Res. Lett., 38, L09805, doi:10.1029/2011GL047036.

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