Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cloud cover unaffected by cosmic rays

10.03.2010
Changes of cosmic rays caused by variations of the solar activity on time scales of a few days do not induce any changes of the global or regional cloud cover. This is concluded from a recent analysis performed by a Swiss-German collaboration. Thus, it is unlikely that cosmic rays influence climate. (Geophysical Research Letters 37, L03802, 03.02.2010)

Clouds play a double role in the Earth's climate. On the one hand, they reflect back to space sunlight shining on the Planet; on the other hand clouds reduce the heat radiation from the Earth's surface into space. Depending on their altitude and properties, therefore, clouds are effectively warming or cooling climate. According to the present perception, the net effect is cooling.

Some years ago, Danish scientists hypothesized that galactic cosmic rays influence the global cloud cover. They derived this hypothesis by evaluating cosmic ray and cloud data over a solar cycle. During an 11-year solar cycle, the Sun's activity and thus the sunspot number increases and decreases again, which causes the strength of the magnetic fields, frozen in the solar wind and deflecting cosmic rays, to vary accordingly.

As a consequence less cosmic radiation reaches Earth at high solar activity. Since the overall solar activity increased during the last century, the Danish authors assumed that the cloud cover and hence the cooling by clouds decreased. They speculated that this effect represents a major cause of the observed global warming. An intense, controversial and still ongoing debate followed.

To test the cosmic ray cloud connection hypothesis independently, the Swiss-German collaboration (scientists from the University of Bern, from EWAG and Frank Arnold from the Max Planck Institute for Nuclear Physics, MPIK) recently analyzed so-called Forbush decreases. These events, generated by sporadic solar eruptions, are characterized by a sudden decrease of the cosmic rays penetrating into the Earth's atmosphere, which recovers again within a few days. The decrease is similar in amplitude as at the maximum of the solar cycle.

How can cosmic rays influence cloud formation? Clouds evolve from condensation nuclei which then grow to droplets. Such condensation nuclei are aerosol particles which in principle may also form from ions (electrically charged atoms or molecules). The ions in turn are produced by the cosmic rays from neutral air molecules.

The group around Frank Arnold has studied the formation of aerosol particles from ions by laboratory experiments. They found that the atmospheric ions grow preferably via uptake of gaseous sulfuric acid molecules. After sufficient growth, the ions may become stable but still very small aerosol particles. These may grow further, preferably by uptake of sulfuric acid. As demonstrated by MPIK laboratory measurements, gaseous sulfuric acid is formed in the atmosphere from sulfur dioxide, which stems mostly from fossil fuel combustion and volcanism. However, as revealed by aircraft-borne measurements made by MPIK in close collaboration with DLR (German Aerospace Center), sulfuric acid is formed in the atmosphere only rarely in sufficient amounts to allow the tiny aerosol particles to grow to the size of cloud condensation nuclei. Therefore, the limited supply of sulfur dioxide is a bottleneck of cosmic-ray mediated cloud formation.

So it seemed consequential to calculate the ion concentration in the atmosphere from measured data of the galactic cosmic radiation and to compare it with satellite data of cloud cover. As a result of the analysis of 6 pronounced Forbush events it can be stated, that the temporal changes of ion concentration and cloud cover are totally uncorrelated. For no cloud layer, the researchers of the Swiss-German collaboration could find global or regional effects, neither for a single event nor averaged over all 6 events.

The scientists have only taken into account such Forbush decreases that were undisturbed by other effects. They calculated for all 6 events during each 20 days at every 3 hours the ion concentration in a 5°×5° grid over the globe and the entire troposphere. Then they compared these values with the also 3-hourly available satellite data of the cloud cover in 3 altitude layers. They evaluated only relative values to avoid possible systematic measurement errors to play a role. The method is sufficiently sensitive to detect effects on the scale postulated by the Danish scientists.

Original paper:
Sudden cosmic ray decreases: No change of global cloud cover.
J. Calogovic, C. Albert, F. Arnold, J. Beer, L. Desorgher, E.O. Flückiger;
Geophysical Research Letters, Vol. 37, L03802, doi:10.1029/2009GL041327, 2010
Contact:
Prof. Dr. Frank Arnold
Max-Planck-Institut für Kernphysik
Tel: +49 6221 516467
E-mail: frank.arnold@mpi-hd.mpg.de

Dr. Bernold Feuerstein | Max-Planck-Institut
Further information:
http://www.mpi-hd.mpg.de

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>