From The Worldwatch Institute, The Looming Threat of Water Scarcity:
Some 1.2 billion people—almost a fifth of the world—live in areas of physical water scarcity, while another 1.6 billion face what can be called economic water shortage. The situation is only expected to worsen as population growth, climate change, investment and management shortfalls, and inefficient use of existing resources restrict the amount of water available to people, according to Worldwatch Institute’s Vital Signs Online service (www.worldwatch.org). It is estimated that by 2025, 1.8 billion people will live in countries or regions with absolute water scarcity, with almost half of the world living in conditions of water stress.
World population is predicted to grow from 7 billion to 9.1 billion by 2050, putting a strain on water resources to meet increased food, energy, and industrial demands. But there are many other pressures, including increased urbanization and overconsumption, lack of proper management, and the looming threat of climate change. According to the United Nations Food and Agriculture Organization and UN Water, global water use has been growing at more than twice the rate of population increase in the last century.
Climate change will affect global water resources at varying levels. Reductions in river runoff and aquifer recharge are expected in the Mediterranean basin and in the semiarid areas of the Americas, Australia, and southern Africa, affecting water availability in regions that are already water-stressed. In Asia, the large areas of irrigated land that rely on snowmelt and high mountain glaciers for water will be affected by changes in runoff patterns, while highly populated deltas are at risk from a combination of reduced inflows, increased salinity, and rising sea levels. And rising temperatures will translate into increased crop water demand everywhere.
As I so often say online and in my presentations, the primary vector for the impact of of climate change on human beings will be water. Rising sea levels that threaten coastal cities and farmlands; droughts; floods; warmer oceans fueling more severe storms; lack of sufficient cooling water for thermoelectric power plants, etc. It often seems like the cruelest of jokes — we and our economies cannot live without continual control over water, from the vast supply we use for personal, agricultural, and industrial purposes to our need to keep it at bay(!) when nature is at its most violent or simply least convenient. And at the root of our growing problems is our profligate use and emissions of carbon — the basis for life on earth, including us — most notably in the form of the greenhouse gases carbon dioxide and methane.
One of the great mysteries we face regards the timing of our collective epiphany about water and climate. There is no question that this link exists and has very grim consequences for humanity; the question is when will enough people connect those dots and realize that global warming or climate change or climate chaos means much more than air temps a few degrees higher than “normal”, it means severe disruptions to the world’s water cycle and thereby the invalidation of many of the assumptions underlying much of our infrastructure. Notions about there “always” being enough water in a river to cool a nuclear power plant or the ocean “never” rising enough to poison farmland via salt intrusion or simply flood cities suddenly seem painfully quaint. We are changing the world to a state we’ve never seen — Bill McKibben’s Eaarth — one that is no longer compatible with how over seven billion of us currently do almost everything. Through our shortsightedness and greed and blind adherence to ideology and simple ignorance we’ve traded away “forever” for short-term gain.
Is it too late to change course? Absolutely not, which is why so many of us are in this fight. But we’re still in that car, accelerating toward the cliff. We’ve passed the point some distance back when we could have made a comfortable change in speed and direction to avoid a catastrophe, and now must brake and swerve very hard. We might even be at the point, thanks to the thermal disequilibrium we’ve created (the “in the pipeline” warming people always talk about) and our locked-in future emissions of having to take scary, painful, and truly drastic steps, like diving out of the car.
 As I write this, at about 10:00AM, I am confident that locally people are busy shopping online or in dealerships for immense, unneeded SUVs, minivans, and pickup trucks, which will help lock in years worth of unnecessarily high emissions. And I would bet that in the areas hit by drought in the US Midwest and West, or crushed by Sandy, similar purchases are being planned and executed.
 What would “diving out of the moving car” mean, exactly, in the real world of a changing climate? I’ll leave that one as an exercise for you, Dear Reader.