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Cloud study casts doubt over climate models  

A newly published study into the way clouds are formed has cast doubt over some climate models, which may lead the need for substantial revisions in how such models are used in environmental study.

The study, published this week in the journal Nature, found serious shortcomings in the descriptions of the way aerosols – the particles that seed clouds – occur in nature. The work suggests that a significant influence on Earth’s cloud cover is the presence of one or more unidentified organic gases – which could occur naturally or be man-made.

The research could have a significant impact on certain theories to do with climate change as some models use the aerosol gases and the clouds they seed to determine how much sun radiation is reflected back into the atmosphere. This in turn has a cooling effect on the atmosphere.

Jasper Kirkby, head of the CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at Cern, the particle physics laboratory near Geneva, studied various gas mixtures of sulphuric acid, water and ammonia – the three gases thought to give rise to aerosol particles at the low altitudes where clouds form.

But the experiments produced between ten and a thousand times fewer aerosol particles than are observed in nature, meaning an additional gas or gases must be playing a vital role in the process.

“Some additional vapour or vapours, 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.”

In a second discovery, the researchers found that cosmic rays from deep in space can increase the formation rates of aerosols by up to ten-fold in colder regions of the atmosphere. This does still leave open the question of whether or not cosmic rays affect cloud cover across the planet, as the aerosol particles discovered were too small to seed clouds.

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