The base of clouds that form over the north-eastern states of the US have been getting ever higher over the past 30 years. It is a change that could severely disrupt forests in the Appalachian Mountains.
Rising cloud ceilings have been spotted before in other parts of the world. In 1999, scientists found that clouds in the Monteverde cloud forests of Costa Rica were not forming as far down the mountains as they once did.
This effect was initially attributed to rising sea temperatures in the Caribbean, caused by global warming, but in 2001 Robert Lawton of the University of Alabama in Huntsville reported that the main driving force behind the change was warmer, drier air moving up from the lowlands, which had been cleared of trees. The rising cloud ceiling has seriously damaged the cloud forest ecology, causing an alarming decline in populations of toads and frogs
New Scientist 26 March 03
