Like a patch of desert that has had all the moisture absorbed from its surface, large parts of the world are similarly drying up, releasing less moisture than ever before, or none at all.
Evapotranspiration is the movement of water from the land to the atmosphere. Most climate models predicted that this phenomenon would increase with the rise in global warming, and that’s exactly what happened from 1982 to the late 1990’s, according to new research published in the latest edition of the online journal Nature.
But in 1998 this increase in evapotranspiration, which had been measured at seven millimetres per year, slowed dramatically in some locations, and stopped entirely in others. In other words, large portions of our planet are drying up, releasing less water because it’s simply not there anymore.
“This is the first time we’ve ever been able to compile observations such as this for a global analysis,” said Beverly Law, a professor of global change forest science at Oregon State University. Law is co-author of the study and science director of the AmeriFlux network of 100 research sites, which is one major part of the FLUXNET synthesis that incorporates data from around the world.
“We didn’t expect to see this shift in evapotranspiration over such a large area of the Southern Hemisphere,” Law said. “It is critical to continue such long-term observations, because until we monitor this for a longer period of time, we can’t be sure why this is occurring.”
There is a limited amount of data available, locked in to the past couple of decades, for this phenomenon, and the scientists say that they are unable to be sure whether this is a natural variability or part of a longer-lasting global change.
One theory is that, on a global level, the limit of acceleration to the hydrological cycle on land has already been reached. And if that’s the case, scientists believe the consequences could be dire. Results could be reduced vegetation growth, less carbon absorption, a loss of the natural cooling mechanism provided by evapotranspiration, more heating of the land surface, more intense heat waves and a “feedback loop” that could intensify global warming.
Some of the areas suffering from this lack of increased evapotranspiration include southeast Africa, much of Australia, central India, large parts of South America, and some parts of Indonesia, and while some of these areas are naturally dry, some are tropical rain forests.
Source: University of Oregon
Image Source: Shiny Things via flickr