Global Warming; Freshwater, Saltwater

Will fighting over freshwater replace fighting over oil? The snowpack in mountains has been exploited by humans since the beginning of civilization. The slow release of water as the snowpack melts provides not only drinking water but also water for irrigation of crops where seasonal rainfall is insufficient.

Billions of people around the world depend on melt water. The regions which include the western United States, Alpine Europe, Central Asia and downstream of the Himalayas and Tibetan Plateau contain nearly nearly half the human population of the planet. Global warming is threatening the timely delivery of freshwater. More cold season runoff can overwhelm reservoir storage of water, and less warm season runoff means less water for irrigation during the growing season.

Researchers at Stanford have published a paper examining the projected impact of global warming and water resources, especially those related to the snowpack in the northern hemisphere. Using the average and extreme rates for precipitation, accumulation and runoff for the 30 years from 1976 to 2006 as a baseline, they then used computer modeling to project out through the 21st century.

They found that as global warming intensifies, low snowfall years will increase, and the snow melt will occur sooner, disrupting water management. “”While the greatest impacts are likely to occur at higher levels of global warming, our results highlight the fact that continued emissions over the next few decades are likely to substantially reduce snow accumulation in a number of regions, increasing the risk of both flooding and drought in different parts of the year,” said the lead author of the paper.

A second, obvious threat posed by global warming is the melting of ancient land bound ice. As the ice reservoirs on the antarctic continent, Greenland, and other interior glaciers melt away, sea levels will rise threatening the great coastal cities of the world. Sea level rise is happening now and recent data suggests that it is happening at an accelerating rate.

Based on long term measurements of tidal gauges and more recent satellite data, on average the rate of sea level rise from 1880 to 2013 has been 0.06 inches per year. If one looks at more recent data however the rate of rising is much greater, over twice as fast. Looking at data from 1993 to the present shows a rate of change of sea level of 0.14 inches per year. Taking account of the accelerating rate of change of sea levels, experts predict a sea level rise of up to 6 feet by the end of the century.

It is extremely difficult to stop the seas from rising but by active approaches to slow global warming we can slow the rate of change of sea levels, giving us more time to protect coastal populations through mitigation.

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