Extreme weather, excess rain

A study shows clearly for the first time the human influence on the climate affects the water cycle, going beyond the bounds of typical physical responses such as warming deep ocean and sea surface temperatures or diminishing sea ice and snow cover extent. It also warns of extreme rainfall and floods as the global temperature continues to climb.

It examined daily records from more than 6,000 weather stations around the globe of rainfall, snowfall and other precipitation stretching from 1951 to 1999. In each year of that period, the team determined how extreme precipitation had been. By compiling the information from all these years and comparing it with the precipitation patterns predicted by computer models of the climate, the scientists noted a similar pattern emerging in the real-world data.

The bad news is that such record-breaking downpours, blizzards and sleet storms are likely to continue to get worse as atmospheric greenhouse gas concentrations continue to rise, causing global temperatures to continue to warm and making the atmosphere more and more humid.

Warmer atmospheric air means more water vapor, which is itself a greenhouse gas, exacerbating the problem. What goes up, must come down and, more and more, that water vapor is coming down in extreme precipitation events. Water vapor increases by roughly 7 percent for every degree Celsius of warming in the lowest level of the atmosphere—or, more simply put, warmer air means warmer water, which means more of it in the form of vapor and hence, more rain and floods. More of what happened in Australia, Pakistan and Sri Lanka!