(June 2, 2011) But how is this possible? Some experts say, “balderdash”; a new study shows otherwise.
The biggest split in the global warming debate lies between earth scientists, who believe that humans dominate temperature changes on Earth, and space scientists, who believe that the Sun is responsible.
How could the Sun be responsible? The hottest theory involves cosmic rays that enter Earth’s atmosphere. These rays bombard minute aerosols in the atmosphere, ionizing them and thus attracting to them water vapour present in the atmosphere. These aerosols, when they become large enough, seed clouds, the theory goes. The more cosmic rays that reach the Earth’s atmosphere, the more clouds and the cooler the planet.
And what determines how many cosmic rays bombard Earth’s atmosphere? The Sun, whose magnetic field, when strong, acts as a shield by deflecting incoming cosmic rays away from Earth. When the Sun’s magnetic field is weak – this is when we see few sunspots – more cosmic rays reach our atmosphere, creating more clouds and cooling the planet.
“This is balderdash,” say earth scientists. “Cosmic rays don’t seed clouds. And even if they did, you’d never be able to prove it.”
Except, according to a study published last month in the respected Geophysical Research Letters, a team of UK and Danish scientists have just taken a giant step toward doing it. By firing a particle beam into a small pressure chamber filled with the gases present in the atmosphere where clouds are formed, the scientists produced tiny aerosol clusters, just as their theory predicted. The clusters they produced – 3 nm in width – aren’t conclusive proof, though. To act as seeds for clouds, they need to get the clusters to grow to at least 100 nm, and for that the experiment would need to be done in a larger pressure chamber.
That experiment is now being done, by CERN, one of the world’s largest research organizations.
For illustrations on how cosmic rays from space create clouds, and more detailed description of the experiments, click here.