Cosmics Leaving Outdoor Droplets or the CLOUD is an experimental facility being run at CERN by Jasper Kirkby to investigate the microphysics between galactic cosmic rays (GCRs) and aerosols under controlled conditions. The experiment began operation in November 2009. But there are other important experiments taking place at CERN, including research designed to help resolve one of the biggest uncertainties of climate change — how clouds form and what role they play in regulating Earth’s temperature. The first results from the lab's CLOUD experiment published in Nature in 2011 confirm that cosmic rays spur the formation of clouds through ion-induced nucleation. Current thinking posits that half of the Earth's clouds are formed through nucleation. Ultimately it is desired to know the recipe for cloud formation, a phenomenon that is not fully understood.
In an interview at CERN with Yale Environment 360 contributor Rae Ellen Bichell, Kirkby talks about cosmic rays, discusses the pitfalls of geoengineering the planet by trying to mimic the formation of clouds, and explains why his experiments in a sterile steel box could help clear up uncertainties about climate change. "We’ve got to reduce that uncertainty if we’re to really sharpen our understanding for future climate projections," says Kirkby.
In meteorology, a cloud is a visible mass of liquid droplets or frozen crystals made of water or various chemicals suspended in the atmosphere above the surface of a planetary body. These suspended particles are also known as aerosols. Clouds in earth's atmosphere are studied in the cloud physics branch of meteorology. An aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke.
The point of the CERN CLOUD experiment, which has involved thousands of experimental runs over the course of the past three years, is to figure out how clouds are formed in the air. Knowing that will allow scientists to figure out what aerosols do to cause cloud formation and what are the appropriate limits and controls.
There are two sources of these aerosol particles. Half of them are coming from particles made on the Earth’s surface, namely sea spray, dust from deserts, or biomass burning. But the other half are coming from a very poorly understood process which involves the condensation of very, very minute amounts of vapors in the atmosphere, which condense to form tiny molecular clusters, which then may grow further and eventually become big enough to seed cloud droplets. These vapors are present in the atmosphere at extremely low levels — typically at the level of one in a million million molecules.
The other area where CLOUD will reduce uncertainty in current climate change is to what extent there can be a natural contribution to the current warming. The current understanding is that natural warming is very, very small. There’s a short-term contribution from volcanoes, which only lasts a few years.
The sun output also varies over time. It is a small variation but significant for us on Earth.
Clouds themselves can reflect light and have a significant effect on warming trends. But how much is natural and how much is man made? That is what the CERN CLOUD experiments are trying to learn.
CLOUD image via CERN.