On December 7, leading experts from all over the world will convene at the UN Climate Change Conference in Copenhagen and attempt to find a solution to global warming. This increasingly serious problem stems from what is called the greenhouse effect, in which a cloud of gases, primarily carbon dioxide, envelop the earth - like the transparent roof of a greenhouse - allowing the sun's rays to penetrate but trapping heat inside.

Global warming has in effect taken the planet back some 15,000 years, to the end of the last ice age.

Until then, for approximately 30,000 years, due to the angle of the earth's orbit around the sun, polar glaciers spread out over the planet; indeed, those of the North Pole then covered a large part of what are today Europe, Asia and America.

Rainstorms moved southward and the northern expanse of the Sahara Desert, which is arid today, was covered with trees and lakes, where such creatures as hippopotamuses and crocodiles lived.

The storms that raged at the time stirred up dust clouds from the drier part of the planet and they reached as far as the Middle East.

Rains deposited sand in the form of brown layers of loess in the area of the northern Negev.

When this latter ice age ended, sand swept up by the Nile River began to cover the Sinai Desert and western Negev.

Today the same section of the Negev that is not composed of exposed rock is covered with layers of loess and in some parts, with sand dunes.

The rainstorms of that era filled the subterranean strata of the Sahara and of our region with water; some of it is salty, but a large amount of it is potable. It has been found that saltwater is suitable for irrigation of plants that tolerate salinity, such as dates, olives, pomegranates and fruitless trees that can be used for lumber, such as the tamarisk, as well as trees whose fruit can be used to produce oil, such as the jojoba.

Evidence of this salty water was discovered by the author of these words and his team after the Six-Day War in 1967.

At first, we endured no little mockery when we began our research, but when our explanatory drilling verified the accuracy of the findings, the doubters were silenced.

But what does the Copenhagen conference, the latter ice age and sandstorms have to do with the "invasion" of sand dunes and the presence of water beneath the deserts?

Ice age groundwater

I will start by relating that my late colleague, Prof. Hugues Faure of the University of Marseilles in France, who studied Saharan terrain and groundwater resources, calculated that if we used the groundwater beneath that desert for irrigation, and restored the greenery that covered it during the last ice age, the vegetation would absorb all the carbon generated by industry each year. According to his calculations, the water supply could last a few hundred years.

In light of his findings, I convened a group of experts on water in arid areas at UNESCO's offices in Paris in 1998, after which we published a manifesto urging a worldwide campaign to plant trees in desert areas.

Studies conducted since then in the Yatir Forest in the southern Judean Desert, by teams led by Prof. Dan Yakir from the Weizmann Institute of Science and from the Desert Research Institute at Sde Boker, indicate that in addition to the trees functioning as a trap for the huge amounts of carbon in the air, and as a means for transforming it into a substance that can help them grow, the stomata (pores) of the trees' leaves do not have to open to absorb the large amount of carbon dioxide in the air.

Thus the amount of water secreted from the leaves is reduced, and the tree saves water and is able to grow even in relatively dry regions.

And there is more to it: The shade provided by the trees planted in sandy expanses reduces the evaporation of the little rain that falls in the desert.

Helpful olive groves

To the amount of carbon absorbed by pines, eucalyptus trees and tamarisks in the Negev forests, we can also add the carbon absorbed by the olive groves now spreading across the northwestern Negev and irrigated by saline groundwater, and the carbon that will be absorbed by the groves and forests that will be planted in the future, in the wake of hydrological studies in the Negev.

Undoubtedly, in Copenhagen, the Israeli delegation will be reminded by others of the fact that most of the State of Israel's energy is produced by burning oil and coal, which emit carbon dioxide, and that it must reduce these emissions.

In response the delegation will certainly point to studies being done to find environmentally friendly energy sources.

At the same time, it would be helpful if the delegation would also note the quantities of carbon being absorbed today, thanks to Israel's forestation efforts, as well as plans to expand the groves and forests in the Negev.

The planting of such vegetation will not only help regulate the amount of carbon in the atmosphere and have economic benefits: It will also serve as a basis for research, which will provide the means for helping residents of Third World countries bordering on deserts - which suffer drought and famine as land dries up due to global warming - to reap the benefits of such a process themselves.

It is only fitting that, at the Copenhagen gathering, the Israeli delegation declare the government's intention to transform the sites slated to be planted with vegetation in the Negev into educational models for the unfortunate people of these arid regions.

These people will then return home and teach the fellow residents how to utilize the groundwater resources located beneath the desert.

This process would transform such regions into a source of both food and raw materials for the poor populations in the world, as well as helping to absorb carbon emissions that are causing global warming.

Furthermore, the countries of the world that are responsible for the creation of greenhouse gases should be asked to help by funding this pioneering effort.

The author is professor emeritus at Ben-Gurion University of the Negev's J. Blaustein Institute for Desert Research.