New research, reported in the journal Nature, confirms the global increase in humidity found in previous studies and that humidity is increasing in a pattern consistent with man-made climate change. The research shows that the pattern of humidity increases in various parts of the world resembles that projected by computer models of man-made global warming. Water vapour is a greenhouse gas, and it is thought that having more of it in the air could amplify temperature rise. The major IPCC report released earlier this year said that this amplification was the largest “positive feedback” mechanism they had identified. Previous research has shown that humidity increases in Europe, a response to higher temperatures, were amplifying the temperature rise by about a factor of two.
Although an upward trend in atmospheric water vapour in the late twentieth century has been previously reported, this study is the first to link the increase directly to anthropogenic warming. The findings have important implications for understanding future increases in atmospheric humidity, which would be likely to influence the intensity of precipitation and tropical cyclones, as well as effecting human heat stress and water availability.
(Some of the scientific team were involved in another study, reported in July, which showed that human-induced climate change was behind trends of increasing and decreasing rainfall noted in various parts of the world.)
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