Desertification may have retarded global warming by 20%

In 'Science' article, Weizmann scientists discuss analysis of Yatir Forest findings.

desert (photo credit: DR)
(photo credit: DR)

Researchers at the Weizmann Institute of Sciencein Rehovot recently made a surprising discovery about the abilities offorests to combat global warming.

In an article published on Friday in the journal Science,Prof. Dan Yakir and Dr. Eyal Rotenberg of the Environmental Sciencesand Energy Research Department discuss their analysis of findings fromthe Yatir Forest research station.

By looking at the other side of the equation, the tworesearchers discovered that desertification was not necessarily all bad- in fact, it may have retarded global warming by as much as 20%. Thedesert reflects sunlight and releases infrared radiation, which has acooling effect. And in a world in which desertification is continuingat a rate of about six million hectares a year, that news might have asignificant effect on how we estimate the rates and magnitude ofclimate change.

The Yatir Forest station sits on the edge of the Negev Desert,a semi-arid zone. While forests are commonly believed to be excellent"carbon sinks," sucking up the carbon dioxide in the atmosphere, whichis thought to contribute to global warming, the two scientists havediscovered other, potentially significant, opposing effects. Whileforests do constitute good carbon sinks, semi-arid forests also absorband trap more of the sun's rays than surrounding shrub land, theyfound, thus contributing to surface heating.

Semi-arid forests also transfer heat from the treesinto the surrounding air to stay cool, causing more surface warming aswell, the two found.

The Weizmann Institute has been operating the research stationfor 10 years, as part of a worldwide project comprised of more than 400stations and called FLUXNET, which investigates the relationshipbetween forests, the atmosphere and climate around the globe.

TheYatir station is unique because it "is one of very few in the semi-aridzone, which covers over 17 percent of the earth's land surface, and ithas the longest record of the processes taking place in semi-aridforests," according to Yakir.

"Although the numbers vary with location and conditions," Yakirsaid in a statement, "we now know it will take decades of forest growthbefore the 'cooling' CO2 sequestration can overtake these opposing'warming' processes.

"Overall, forests remain hugely important climate stabilizers(not to mention the other ecological services they provide), but thereare tradeoffs, such as those between carbon sequestration and surfaceradiation budgets, and we need to take these into consideration whenpredicting the future," Yakir said.