If there is perhaps an even more serious consequence of global warming than rising sea levels, it is the shortage of water that will follow the melting of the glaciers. Glacial meltwater feeds most of the planet’s major rivers today. The Yellow River, the Mekong, the Ganges, and the Indus—which together irrigate areas inhabited by two billion people—all have their source in the glacial waters of the Himalayas.
As the glaciers melt, the first consequence will be too much water. Mountain regions will experience sudden and catastrophic flooding. At slightly lower altitudes, the arrival of the monsoon will precipitate flooding that is slower but more widespread. By about 2050, floods could reach a peak, with rivers overflowing and devastating the farmlands and communities that lie along their banks. Asia is not the only continent at risk: Europe has also seen catastrophic flooding—in France in 1999, and in Central Europe in 2002 and 2005. And developments are similar in South America, in Andean and neighboring regions.
At a later stage, water will start to become scarce. Global warming shortens winters and reduces the quantity of snow falling on high ground. Ice that traditionally melted in summer to feed lakes and rivers will no longer be replenished. According to a number of forecasts, India’s major rivers could become seasonal during the second half of the 20th century. This despite the fact that the Brahmaputra, to mention only one, has a rate of flow 100 times greater than European rivers such as the Seine, the Ebro, and the Tiber.
Aside from agriculture and reserves of drinking water, water shortages also threaten energy production because of a reduction in the energy supplied byhydro-electric dams and because of cooling problems at thermal power stations.
Even if we take the radical measures that are needed to halt the process of global warming, the phenomenon has an in-built time lag. It will continue to get worse for several decades before the first measures take effect—and that is assuming that we do not just bury our heads in the sand. Either way, we are going to have to adapt to a different world. We may need to evacuate areas most at risk, change our farming practices, and put in place new methods of managing our water resources.