We learn that warm air rises and cool air sinks. This is basic science. A new study found circumstances in which cool air rises in tropical areas. Cold air rises because of the lightness of water vapour. In humid climates, water particles become lighter and help cool air rise. A researcher said: "Water vapour has a buoyancy effect which helps release the heat of the atmosphere to space and reduce the degree of warming."

Scientists say humid air is lighter than dry air at the same temperature. Cooler air with water droplets rises to make clouds and storms. Rain cools tropical areas. More research is needed to find out how rising cool air affects 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."