In much of the Western US (where I grew up), drought is by far the most important threat from climate change. Wars over water rights have been raging since the Los Angeles Aqueduct was built in the 1920s to bring water from the eastern slope of the Sierra Nevada to Los Angeles, drying up Owens Lake and producing toxic dust storms. In addition to precipitation droughts and soil moisture droughts and hydraulic droughts, we likely have "WATER-USE DROUGHTS". Water-use may be the biggest cause of drought, especially if increasing transpiration with temperature is being poorly modeled. Your information (in #13) about the current "greening" of the planet and the "greener" Pliocene Warm Period raised serious doubts in my mind that warmer must be drier. I'd like to know more about the models used to quantify soil moisture droughts and the data that shows increasing water vapor deficits.

Anecdotal stories say that rivers that formerly flowed year-round in Northern China apparently no longer reach the ocean much of the year due to water usage. Lakes Mead and Powell (reservoirs) on the Colorado are at record lows - fundamentally because water has been released from them feed the Colorado River Aquaducts (LA, San Diego and the Imperial Valley) and the Central Arizona Project. Yes, these reservoirs are also falling because inflow from the Upper Colorado Basin has not matches these outflows, but water from the Upper Basin is also used to supply areas outside the Upper Basin (Denver, Colorado Springs , Albuquerque, Salt Lake City, and Cheyenne). Phoenix is the fastest growing city in the US (now fifth largest) and the population in the Colorado Basin has more than doubled since 1985. Does the IPCC distinguish between drought associated with climate change and water-use?

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