2010-10-13 02:04:58Land 'evapotranspiration' taking unexpected turn: huge parts of world are drying up


This caught my eye because our JohnD so frequently manages to steer conversation to this topic: 

"CORVALLIS, Ore. – The soils in large areas of the Southern Hemisphere, including major portions of Australia, Africa and South America, have been drying up in the past decade, a group of researchers conclude in the first major study to ever examine "evapotranspiration" on a global basis.

Most climate models have suggested that evapotranspiration, which is the movement of water from the land to the atmosphere, would increase with global warming. The new research, published online this week in the journal Nature, found that's exactly what was happening from 1982 to the late 1990s.

But in 1998, this significant increase in evapotranspiration – which had been seven millimeters per year – slowed dramatically or stopped. In large portions of the world, soils are now becoming drier than they used to be, releasing less water and offsetting some moisture increases elsewhere.

Due to the limited number of decades for which data are available, scientists say they can't be sure whether this is a natural variability or part of a longer-lasting global change. But one possibility is that on a global level, a limit to the acceleration of the hydrological cycle on land has already been reached."





2010-10-13 02:46:44

So are they saying that some areas have gotten all dried up already?
2010-10-13 02:56:41yes
Dana Nuccitelli
Yes, it sounds like what they're saying is that some areas have dried so much that they don't have sufficient soil moisture remaining to continue accelerating evapotranspiration, assuming this is part of a long-term trend and not just a short-term natural cycle or something.
2010-10-13 07:54:11

As a first impression I thought it was in contradiction with the river discharge data. But looking at the annual river discharge in the inset of the figure I noticed that indeed there has been a decline in the last decade. Very few and noisy points, to be honest, but at least there's no blatant contradiction.