Friday, July 31, 2009

Is Climate Change Greening the Sahel?

Scientists are now seeing signals that the Sahara desert and surrounding regions are greening due to increasing rainfall.

If sustained, these rains could revitalize drought-ravaged regions, reclaiming them for farming communities.

This desert-shrinking trend is supported by climate models, which predict a return to conditions that turned the Sahara into a lush savanna some 12,000 years ago.

The green shoots of recovery are showing up on satellite images of regions including the Sahel, a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles (3,860 kilometers).

Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.

The study suggests huge increases in vegetation in areas including central Chad and western Sudan.

The transition may be occurring because hotter air has more capacity to hold moisture, which in turn creates more rain, said Martin Claussen of the Max Planck Institute for Meteorology in Hamburg, Germany, who was not involved in the new study.

"The water-holding capacity of the air is the main driving force," Claussen said.

He added that the greening trend is supported by other satellite data.

If true, this would suggest one of two things. The first is that the models that indicate that up to 2 or 3 C increases will result in greater precipitation and then a drying out higher than that. Or it might hint that the Neo-Eocene scenario might be more accurate than the Neo-Oligocene.

1 comment:

Leo Lane said...

One aspect not considered is the increase of carbon dioxide in the atmosphere.

It is now 388 ppm, up from 270 ppm not so long ago.

The increase has the effect of stimulating plant growth, and reducing the amount of water necessary for growth.

If CO2 were to drop to 200 ppm, plant life would be marginal, with serious consequences to all life on earth.