AlphaGalileo is a service for the media.
Journalists should register for free access to embargoed
news and press office contact information.
Please register view details
Please register to view contact details
Please log in or register to view articles older than 3 months
This item is under embargo and is only visible to journalists
Bookmark this item in My Area
This item is bookmarked
Add comments to this news release
PLEASE NOTE THIS ITEM IS EMBARGOED!!!
EMBARGO: 19 December 05:00 US Eastern (24hr) / 10 am GMT
A breakthrough in the understanding of how cosmic rays from supernovae can influence Earth's cloud cover and thereby climate is being published in the journal Nature Communications (19 Dec.).
The study reveals how atmospheric ions, produced by the energetic cosmic rays raining down through the atmosphere, helps the growth and formation of cloud condensation nuclei – the seeds necessary for forming clouds in the atmosphere. When the ionization in the atmosphere changes, the number of cloud condensation nuclei changes, affecting the properties of clouds.
More cloud condensation nuclei means more clouds and a colder climate, and vice versa. Since clouds are essential for the amount of Solar energy reaching the surface of Earth the implications can be significant for our understanding of why climate has varied in the past and how future climate changes could evolve.
Cloud condensation nuclei can be formed by the growth of small molecular clusters called aerosols. It has until now been assumed that additional small aerosols would not grow and become cloud condensation nuclei, since no mechanism was known to achieve this.
The new results reveal, both theoretically and experimentally, how interactions between ions and aerosols can accelerate the growth by adding material to the small aerosols and thereby help them survive to become cloud condensation nuclei. It gives a physical foundation to the large body of empirical evidence showing that Solar activity plays a role in variations in Earth’s climate. For example, the Medieval Warm Period around year 1000 AD and the cold period in the Little Ice Age 1300-1900 AD fits with changes in Solar activity.
“Finally we have the last piece of the puzzle explaining how particles from space affect climate on Earth. It gives an understanding of how changes caused by Solar activity or by super nova activity can change climate,” says Henrik Svensmark, from DTU Space at the Technical University of Denmark, and lead author of the new study.
Co-authors are senior researcher Martin Bødker Enghoff (DTU Space), Professor Nir Shaviv (Hebrew University of Jerusalem), and Jacob Svensmark, (University of Copenhagen).
Deatils on the new study:
The fundamental new idea in the study is to include a contribution to growth of aerosols by the mass of the ions. Although the ions are not the most numerous constituents in the atmosphere the electro-magnetic interactions between ions and aerosols compensate for the scarcity and make fusion between ions and aerosols much more likely.
Even at low ionization levels we see about 5% of the growth rate of aerosols is due to ions. In the case of a nearby super nova the effect can be more than 50% of the growth rate, which will have an impact on the clouds and the Earth’s temperature.
To achieve the results a theoretical description of the interactions between ions and aerosols was formulated along with an expression for the growth rate of the aerosols. The ideas were then tested experimentally in a large cloud chamber.
Due to experimental constraints caused by the presence of chamber walls, the change in growth rate that had to be measured was of the order 1%, which poses a high demand on stability during the experiments, and experiments were repeated up to 100 times in order to obtain a good signal relative to unwanted fluctuations. Data was taken over a period of 2 years with total 3100 hours of data sampling.
The results of the experiments agreed with the theoretical predictions.
The hypothesis in a nutshell:
The implications of the study suggests that the mechanism can have affected:
Full journal reference:
Paper title: “Increased ionization supports growth of aerosols into cloud condensation nuclei”
Authors: Henrik Svensmark, M.B. Enghoff, N. Shaviv and J. Svensmark.
Nature Communications DOI: 10.1038/s41467-017-02082-2
The paper will after the EMBARGO - 19 Dec. 11.00 CET - appear here: http://www.nature.com/ncomms
This item has been withdrawn. Registered users can contact the publishing organisation for further details by logging in