We learn at school that warm air rises and cool air sinks. This is a basic principle of science. A study from the University of California found there are circumstances in which cool air rises. Researchers found that in tropical areas, cold air rises because of the lightness of water vapour. In warm, humid climates, water particles become more buoyant and can help cool air rise. The lead researcher said: "Water vapour has a buoyancy effect which helps release the heat of the atmosphere to space and reduce the degree of warming. Without this lightness...climate warming would be even worse."
Scientists say humid air is lighter than dry air at the same temperature and pressure. This is called the vapour buoyancy effect. Cooler air containing water droplets rises to form clouds and thunderstorms. Rain has a cooling effect in tropical areas. More research is needed to find out the effects rising cool air has on limiting global warming. A researcher said: "Now that we understand how the lightness of water regulates tropical climate, we plan to study whether global climate models accurately represent this effect."