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Man-made global warming is driving up humidity levels, with the risk that rainfall patterns will shift or strengthen, tropical storms intensify and human health may suffer from heat stress, a study released on Wednesday said.
From 1976 to 2004, when the world’s average surface temperature rose 0.49 degrees Celsius (0.9 degrees Fahrenheit), global levels of atmospheric water vapour rose 2.2 percent, according to the paper by British scientists.
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Gillett said water vapour was a “positive feedback” — a vicious circle, in scientific parlance — in the global warming equation.
Steam is a greenhouse gas, meaning that like carbon pollution that results from burning fossil fuels, it traps solar heat in the atmosphere, thus stoking the warming effect and so worsening humidity.