17 September 2012

The Sahara is not in a drought

...but the US is in its worst drought in a long time (H/T to RM).

The drought means less water on the supply side and more demand for water from humans and ecosystems under heat stress.

The drought will not be a problem where supply and demand are in balance, but it will expose areas of imbalance.

What's the solution? In ecosystems, there is death and displacement of "wet" species by "dry" species.

In human systems, there are choices:
  • Change habits, e.g., let lawns die
  • Make do with less, e.g., don't overwater lawns
  • Continue with business as usual (BAU), e.g., overdraft groundwater for lawns 
In my experience, people don't mind using less, but they are happy to carry on with BAU when there are no social or financial signals that change is necessary. They are least likely to change their habits because such changes take more effort or entail higher costs in the short run.

The relevant question, then, is whether drought is a long-run or short-run event. Is the US experiencing a temporary heating and drying -- a dry summer before normal winter rains -- or a permanent shift to hotter summers and drier winters?

My understanding is that climate change is going to give us more heat AND more rain, but those rains will be in the wrong places, in the wrong volumes and at the wrong times. That means that we will have a hard time benefiting from stronger hydrological flows and that we may not be able to use "extra" water to reduce the damages from higher temperatures.

Bottom Line: We'd best prepare for an age of permanent drought deserts.

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