Satellite photos show southern areas of the Sahara Desert have been greening over the past 15–20 years—confounding the climate models’ predictions that global warming would massively expand the deserts. Farouk al-Baz of Boston University told the BBC World Service, “The desert expands and shrinks in relation to the amount of energy that is received . . . from the sun . . .  over many thousands of years.”

 

We know the Sahara was much wetter 10,000 years ago when Stone Age hunters drew pictures of hippos and crocodiles on Saharan cave walls while Kenya was left dryer. The Sahara was also was wetter during the Roman Warming (200 BC to 800 AD) when the Romans imported huge amounts of wheat from the then well-watered fields in North Africa.

 

Out in the Central Pacific, chemical oceanographer Julian Sachs from the University of Washington was recently examining sediments under a fresh-water lake on a coral atoll near the equator. Suddenly, the layers of brown, coffee-colored mud gave way to a layer of strawberry jam-colored mud. He knew immediately it had been created by cyanobacteria that only live in super-salty water. That meant the atoll, which currently gets heavy tropical rains, had once been much drier.

 

“We knew right then that there had to have been a massive change in the climate regime,” said Sachs. Carbon dated it to the 17^th century, which meant the massive tropical rain belts hovered right near the equator during the 1600s, Sachs reports in Nature Geoscience. It was the depths of the Little Ice Age, with a sun one-tenth  as active as today’s. The team found similar evidence on other equatorial islands, including the Galapagos and Palau in the Philippine Sea.

 

More recently, says Sachs, the tropical rain band has moved northward about 300 miles.

 “If the Intertropical Convergence Zone was 550 km south of the present position as recently as 1630,” says Sachs, “it must have migrated northward just less than a mile a year.”  If that continues, he expects it to be 75 miles further north by the end of the century—as the Modern Warming continues for another century or four.    

 

Patrick Nunn of the University of the South Pacific in Fiji has already documented the Pacific beginnings of the Little Ice Age about 1300 and says it marked a radical shift from times of plenty to times of famine throughout the Pacific.

 

The global warmings have been the good times for humans; that’s the historic pattern of the 1500-year solar-linked Dansgaard-Oeschger climate cycle. The warm phase of the cycle elevates temperatures in the Arctic by as much as 6 degrees C, and in the temperate regions by 1-3 degrees C. Temperatures at the equator don’t change much, but the tropical rain belts shift the deserts and wet spots.

 

The tropical rainfall patterns certainly rank as a key piece of evidence on whether the recent high world temperatures are being driven to dangerous levels by fossil fuels, or are part of the natural, moderate solar-linked cycle.

 

With the planet now cooling, we have time to learn more—before we pay trillions of dollars to eliminate fossil fuels and then find the effort was useless.  

 

DENNIS T. AVERY is an environmental economist, and a senior fellow for the Hudson Institute in Washington, DC.  He was formerly a senior analyst for the Department of State. He is co-author, with S. Fred Singer, of Unstoppable Global Warming Every 1500 Hundred Years, Readers may write him at PO Box 202, Churchville, VA 24421 or email to cgfi@hughes.net

 

Sources:

 

Southern Sahara greening:  Ayisha Yahya, “Are the deserts getting greener?”, BBC News, July 16, 2009;  Ker Than, “Deserts Might Grow as Tropics Expand,” LiveScience, Fox News.com, May 25, 2006.

Sahara Lush and Populated:  Bjorn Carey, “Sahara Desert was Lush and Populated Only Temporarily,” LiveScience, Fox News.com, July 24, 2006.: 

On the shifting tropical rainbelts in the Pacific: Emily Sohn, “Shifting Rains Impact Pacific Islands.” Discovery News, July 10, 2009; “Tropical Rainfall Moving North,” LiveScience, Fox News.com,  July 2, 2009;  Patrick Nunn, et al., “Times of Plenty, Times of Less: Last-Millennium Societal Disruption in the Pacific Basin,” Human Ecology , Jan 5, 2007.