Global Warming and the Rub’ al-Khali

A respected geologist and desert expert says global warming could result in an improved climate for the Rub’ al-Khali and other great deserts of the world.

Kenneth W. Glennie, former Shell geologist and Arabian desert specialist, suggested a possible return to “the ideal conditions of the Climatic Optimum” of six to nine thousand years ago, when the Empty Quarter enjoyed milder temperatures and boasted freshwater lakes, thriving vegetation and wildlife.

If global warming causes a melting of major ice sheets, sea levels should rise and weather patterns should change, resulting in more rainfall in the major desert belts accompanied by milder temperatures, according to the geologist.

Glennie set forth this counter-intuitive theory in his book, The Desert of Southeast Arabia. He says oxygen isotope studies have shown that when glacial ice sheets expand, as during the Ice Ages, global sea levels drop, land aridity increases and deserts grow.

In his words:

To judge from climatic changes over the past million years or more, the long-term trend for the World ought to be a reversion to the extensive high-latitude glacial conditions, and this implies increasingly arid conditions over most of the desert belts. A new, and therefore incompletely proven factor, is the influence of ‘Global Warming’ and the ‘Greenhouse Effect’, which many scientists claim to be largely the result of man’s misuse of fuels and chemicals. If correct, this could have the opposite effect to the above prediction in that existing ice sheets would melt even further, a rise in global sea level would reduce the area of land, and the existing desert areas that remained above sea level would become less arid, perhaps with a return to the idyllic conditions of the Climatic Optimum. 

Glennie says oxygen isotope data indicates that after the interglacial peak of 120,000 years ago, the global sea level fell “rather erratically” until about 17,000 years ago, when a dramatic rise in sea level until about 6,000 years ago brought the level to slightly higher than today.

During the 100,000 years of falling sea level “we have little idea of the associated changes in climate that almost certainly occurred, although eventually it may be possible to piece together fragments of that history with accurate dating of some of the alluvial fan sequences,” Glennie says. “Globally, however, there is evidence that higher rainfall in today’s desert belts alternated with extremes of aridity…”

During periods of interglacial high sea level, Arabia’s climate was probably much more humid than now. “These high sea levels seem to have been relatively exceptional,” he says, “and alternated with generally longer periods of lower sea level with increased areas of land and enhanced aridity.”

Following the ideal conditions of the Climatic Optimum between 9,000 and 6,000 years ago, the world’s deserts seem to have become slightly more arid again. Rainfall and vegetation have decreased and winds have probably become slightly stronger and more persistent, or at least more effective at moving sand because the increased aridity, according to the geologist.

Former Aramco geologist Hal McClure described the formation of ancient lakes during “less arid” periods in the Rub’ al-Khali in his 1984 doctoral thesis for the University of London.  As reported in Aramco World magazine:

In fact, evidence indicates that lakes formed twice: once from roughly 37,000 to 17,000 years ago, and then again from around 10,000 to 5,000 years ago. In the interim, "hyper-arid," period, as today, rain was very rare.McClure theorizes that the lakes were created by cataclysmic rainfall, like that seen in the summer monsoons which today water the Indian subcontinent and, on the Arabian Peninsula, extreme southern Oman. He speculates that the summer monsoon moved to the north twice in recent geological history, most likely creating lakes in what he calls "one-time fill-up incidents."
"It would rain like hell one monsoon season and then not rain in a particular area for the next 10 or 100 years," he says. The lakes had no links with rivers, above or below ground, or any other source of continuous replenishment, and their bed sediments present no evidence of regular refilling.Rub' al-Khali lakes "weren't enormous lakes like in East Africa or like Lake Superior," explains McClure. They probably ranged in depth from two to 10 meters (six to 32 feet), he says, though some were only "ephemeral puddles." A few may have lasted several years, but most existed only "a few months to a few years."

Geologist Glennie was born in Scotland in the United Kingdom. He had a long career with Shell as a desert expert, and has won numerous academic and professional honors. In 2005 he received the Sidney Powers Memorial Award, the most distinguished honor of the American Association of Petroleum Geologists (AAPG).