In de loop der tijd heb ik verschillende malen aandacht geschonken aan de Svensmark–hypothese. Zie hier en hier.

Volgens deze hypothese hebben de veranderingen in zonne–activiteit een belangrijke invloed op de kosmische straling die de aarde bereikt, die op haar beurt weer invloed heeft op de wolkenvorming en daardoor op het aardse klimaat. Zowel protagonisten als antagonisten van de menselijke broeikashypothese (AGW = ‘Anthropogenic Global Warming’) achtten deze hypothese niet voldoende bewezen. Nieuw onderzoek, uitgevoerd door CERN onder leiding van Jasper Kirkby (zie afbeelding boven), dat overigens niet specifiek op dit mechanisme was gericht, lijkt toch weer steun voor deze hypothese te hebben opgeleverd.

Onder de titel, ‘Scientists make news clouds which may lessen global warming’, rapporteerde ‘The Daily Star’:

A new discovery about how clouds form may scale back some of the more dire predictions about temperature increases caused by man-made global warming.

That’s because it implies that a key assumption for making such predictions is a bit off.

“What this will do is slightly reduce and sharpen the projections for temperature during the 21st century,” said researcher Jasper Kirkby.

Nonetheless, he added, “We are definitely warming the planet.”

Kirkby works at the European Center for Nuclear Research, or CERN, near Geneva. He is the lead author of one of three studies on the topic released Wednesday by the journals Nature and Science.

Essentially, the work reveals a previously unknown natural process that in a complex way creates atmospheric particles around which clouds form. The most common source of particles is air pollution, usually sulfuric acid from the burning of fossil fuels. There are also natural sources, but they have been considered far less important for cloud formation.

The new work shows that a combination of cosmic rays from space and gases emitted by trees also creates particles, and then clouds, without man-made pollution. The scientists witnessed this in a cloud simulation chamber and from a Swiss mountaintop observatory more than two miles high (3.5 kilometers).

“This process is only effective in pristine environments and there are very, very few pristine environments left on Earth,” Kirkby said. Nowadays, the process is overwhelmed by pollution particles.

…. it would mean that greenhouse gases haven’t been quite as potent in producing warming so far as scientists thought. So, ton for ton, they may not be quite as potent in producing future warming either.

Kirkby said it’s too soon to tell how much less warming the new study implies. Other recent studies found flaws in climate forecasts because of uncertainty about clouds that would increase, not decrease, possible warming in the future.

Lees verder hier, hier, hier en hier.

Commentaar van een Belgische klimaatscepticus:

Svensmark was right! Cosmic rays have an important role in seeding clouds. Biogenic vapours from pristine environment form aerosols that induce clouds. Cosmic rays have a strong role in reinforcing this mechanism. So the models will have to be revised, and temperature increases by CO2 will have to be decreased!

Voor mijn eerdere bijdragen over klimaat en aanverwante zaken zie hier, hier, hier, hier en hier.