Dry soil may accelerate global warming

A recent decrease in evapotranspiration (ET)– the movement of water into the atmosphere – has been linked to a decrease in soil moisture and has alarming implications for climate change.

According to a report, published this month by Nature Online, a decrease in ET could result in “accelerated land-surface warming” and a “reduced terrestrial carbon-sink”, meaning an increase in both regional temperatures and atmospheric carbon dioxide (CO2).

ET is the movement of water, from soil, plants and water bodies, into the air and as such plays a key part in the water cycle.  ET currently uses more than half of the sun’s energy absorbed by land surfaces and can affect regional temperature and rain fall.

Using satellite and meteorological data, Scientists from Europe and the United States discovered that since 1997 ET rates have decreased. It was discovered that a decrease in ET “is matched by a soil-moisture decrease over large parts of Australia, East Africa and South America”

Previous climate models have predicted ET would continue to increase with global warming. This latest study however, suggests ET rates have a limit, which has already been reached.

However, the authors state “It is hard to evaluate whether this is a natural climate oscillation” or a direct effect of climate change. This is partly due to the limited number of decades for which data is available.

Data compiled from 1982 to 2008 and complex mathematical formulas were used to determine global trends. An initial increase in ET rates were discovered until 1997, however, from 1997 to 2008 these increases either slowed or stopped.

The original report can be found here.

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