Best known for its studies of the fundamental constituents of matter, the CERN particle-physics laboratory in Geneva is now also being used to study the climate. Researchers in the CLOUD collaboration have released the first results from their experiment designed to mimic conditions in the Earth's atmosphere. By firing beams of particles from the lab's Proton Synchrotron accelerator into a gas-filled chamber, they have discovered that cosmic rays could have a role to play in climate by enhancing the production of potentially cloud-seeding aerosols. Describing their findings in this week's Nature, the team has also found that our current understanding of the chemistry of these aerosols is inadequate and that manmade pollution could have a larger role in their formation than previously thought.The climate link is a bit indirect. As we've seen before, the Solar Cycle influences the rate of cosmic ray bombardment of earth. An active solar cycle shields the earth from cosmic rays, while a weak solar cycle allows cosmic rays to penetrate to the earth's atmosphere. If (and this is the IF that CERN was testing) cosmic rays help initiate clouds, then periods of low solar cycle would be cloudier and likely cooler than times of high solar activity. This has been observed in the past but the link was unknown, the actual change in solar radiation from the sun is not reduced enough in the low solar activity periods to account for the difference. Now, it would appear that cosmic rays may provide the link.
The hypothesis was proposed by Henrik Svensmark of the National Space Institute in Copenhagen. It is anathema to global warming activists as it invokes a solar explanation for much of the warming that has been observed in the 20th century.
While it is now established that cosmic rays can, in fact, initiate such aerosol formation, the question of whether such aerosols do grow to initiate cloud formation is unknown. There appears to be some role left for other compound in the atmosphere, including man-made contaminants in the growth of aerosols into clouds. As we say in the business "more work is needed."
Previous posts on the cosmic ray-climate linkage:
Dalton or Maunder?