August 25, 2011
New Research Questions Knowledge About How Clouds Form
Our understanding of how clouds form may need to be revised, according to new research published in the journal Nature.
The research has implications for certain predictions about climate change because aerosol particles and the clouds they seed have a cooling effect on the Earth by reflecting radiation from the sun.
Jasper Kirkby, head of the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment at CERN, studied various gas mixtures of sulphuric acid, water and ammonia. These three gases thought to give rise to aerosol particles at the low altitudes where clouds form.
The experiments produced between ten and a thousand times fewer aerosol particles than are observed in nature, which means an additional gas or gases must be playing a vital role in the process.
"Some additional vapor or vapors, together with sulphuric acid, is controlling the formation rate of aerosols in the atmosphere and so affecting climate, so it is important to identify these and understand whether their sources are natural or associated with human activities," Kirkby told the Guardian.
"If they come from human activities, it raises the prospect of a new climate impact from humans. Alternatively, if they have a natural origin, we have the potential for a new climate feedback. What is clear is that the treatment of aerosol formation in climate models has to be substantially revised."
Aerosols are tiny liquid or solid particles suspended in the atmosphere.
About half of atmospheric aerosols come from the Earth's surface, in the form of dust, sand or sea spray, while the rest are produced in the air when vapor particles condense and grow into clusters.
The researchers found in a second discovery that cosmic rays from the depths of space can increase the formation rates of aerosols by between two and tenfold in some cold regions of the atmosphere.
The team hopes to settle whether or not cosmic rays affect cloud cover and to give a better understanding of how some variability in the Earth's climate might be influenced by rays and the sun's activity.
Academics welcomed the results of the research but said it did not prove cosmic rays were a major driver of climate change.
"This paper is very much only a first step in the quantification of the climate effect of cosmic rays, so it would certainly be wrong to conclude that cosmic rays are a major driver of climate change," Piers Forster, professor of climate change at the University of Leeds, said in a press release.
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