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Most of us learn school that warm air rises and cool air sinks. This has always appeared to be a fundamental principle science. However, a study the University California, Davis found that there are circumstances which cool air rises. Researchers discovered that tropical atmospheres, cold air rises because the lightness of water vapour. Apparently, in warmer and more humid climates, water particles become more buoyant and can help cooler air rise. Lead researcher Dr Da Yang said: "Water vapour has a buoyancy effect which helps release the heat the atmosphere to space and reduce the degree warming. Without this lightness water vapour, the climate warming would be even worse."

The scientists said humid air is lighter than dry air the same temperatures and pressure. This is called the vapour buoyancy effect. It allows cooler air containing water droplets to rise, which then forms clouds and thunderstorms. The resulting rain has a cooling effect tropical areas. Another researcher, Seth Seidel, said more research is needed to find the effects rising cool air has climate change, and its impact on curbing the effects global warming. Seth Seidel said: "Now that we understand how the lightness water regulates tropical climate, we plan to study whether global climate models accurately represent this effect." The study is published the journal "Science Advances".

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