A new cloud on the horizon A new kind of cloud may be coming to a sky near you, and could be the first fresh variety to be officially recognised since 1951. It is a dark, turbulent sort of thing, which folds oppressively over a landscape and looks as if it means trouble. For this reason, and its base of stormy-looking swirls, the world's cloud fanciers have christened it undulatus asperatus (agitated wave). One of the first photographs of it was taken above Cedar Rapids, Iowa, and the image found its way to the UK-based Cloud Appreciation Society (CAS). They put it on their website, and the idea of finding the first new kind of cloud in 60 years took off. Since then, it has been regularly spotted above America's Great Plains, but has also been seen in France, Norway, Perthshire in Scotland, Salcombe in Devon, and Middlesbrough. The CAS took up its cause, named it, and began lobbying for it to be formally recognised as a new sub-species. This is no easy matter. Getting a new kind of cloud recognised depends on the climatic conditions that create it being identified, formal acceptance by the World Meteorological Organisation in Geneva, and inclusion in the International Cloud Atlas. They are not what you might call impetuous, the last atlas being produced in 1975. But the cloud appreciators have not been idle. The CAS has gathered many pictures, and assisted with the necessary academic research, principally conducted at Reading University. Graeme Anderson, a meteorologist, did a thesis on the conditions that cause undulatus asperatus to form, concluding that they were similar to mammatus clouds but with high-level winds shaping the vapour into billowing swirls. The founder and president of the CAS, Gavin Pretor-Pinney, author of The Cloudspotter's Guide, has presented the case to the Royal Meteorological Society, and they have been convinced. Its supporters must wait to see if undulatus asperatus will be classified as the kind of cloud variant called a "supplementary feature" - the first new type since cirrus intortus. And, according to the CAS, "there are rumours that the UN organisation is considering the case for a new edition." Although official recognition may not seem immediate, public interest in clouds is growing. Membership of the CAS has already grown to 30,903 and it is releasing a cloud-watching app next year. The app will be geo-tagged, meaning the locations and times of photographs taken by cloud-spotters can be fed into Reading University systems to help them understand formations. Mr Pretor-Pinney said: "Observing the clouds is an important way of documenting the effect of global warming on the sky. Clouds may provide answers about temperature and climate change in years to come. Besides, cloud-spotting is fun, something made clear by the society's mission statement which includes not only the belief that clouds have been "unjustly maligned," but also a pledge "to fight blue-sky thinking." But then, as US meteorologist Jesse Ferrell once said of clouds: "There's a lot of grey areas." Especially in Britain.