Deserts

Deserts take up about one third of the Earth's land surface. One definition of a desert is an area that receives an average annual precipitation of less than .25 m or an area in which more water is lost to evaporation than falls as precipitation Hot deserts usually have a large diurnal and seasonal temperature range, with high daytime temperatures, and low night time temperatures (due to extremely low humidity). In hot deserts the temperature in the daytime can reach 45 °C or higher in the summer, and dip to 0 °C or lower in the winter. Water acts to trap infrared radiation from both the sun and the ground, and dry desert air is incapable of blocking sunlight during the day or trapping heat during the night. Thus, during daylight most of the sun's heat reaches the ground, and as soon as the sun sets the desert cools quickly by radiating its heat into space.

Many deserts are formed by rain shadows; mountains blocking the path of precipitation to the desert. Deserts are often composed of sand and rocky surfaces. Sand dunes called ergs and stony surfaces called hamada surfaces compose a minority of desert surfaces. Exposures of rocky terrain are typical, and reflect minimal soil development and sparseness of vegetation.

The ever worsening problems of environmental degradation, combined with increasing population makes action imperative to restore deserts to productive use. Agroforestry, irrigated agriculture, mixed species grazing, agri-tourism and other techniques can be used to increase yields and speed recovery. These approaches must also be sustainable.

The largest of the world’s hot deserts is the Sahara 50 which was once verdant but turned to desert over thousands of years rather than in an abrupt shift as was previously believed.

Understanding this process is helpful in predicting future climate change.

There are also signs of a small shift back towards greener conditions in parts of the Sahara 50, apparently because of global warming.

A study of ancient pollen, spores and aquatic organisms in sediments in Lake Yoa in northern Chad showed the region gradually shifted from savannah 6,000 years ago towards the arid conditions that took over about 2,700 years ago.
The findings, about one of the biggest environmental shifts of the past 10,000 years, challenge past belief based on evidence in marine sediments that a far quicker change created the world's biggest hot desert.

Scientists, studying the remote 3.5 sq km Lake Yoa, found the region had once had grasses and scattered acacia trees, ferns and herbs. The salty lake is renewed by groundwater welling up from beneath the desert.

A gradual drying, blamed on shifts in monsoon rains linked to shifts in the power of the sun, meant large amounts of dust started blowing in the region about 4,300 years ago. The Sahara 50 now covers an area the size of the United States.

This improved understanding of the formation of the Sahara 50 might help climate modelers improve forecasts of what is in store from global warming. Some areas will apparently be more vulnerable to drought, others to more storms or floods.
The Sahara 50 got greener when temperatures rose around the end of the Ice Age about 12,000 years ago. Warmer air can absorb more moisture from the oceans and it fell as rain far inland. There are indications this process may be slowly repeating as current temperatures rise. Tens of kilometres of unoccupied desert are now covered by grass where for a long time there was nothing but sand.

Poor regions, particularly Africa, appear at greatest risk from the projected effects of global warming, while their carbon emissions have been small compared to the developed world. At the same time, developing country exemptions from provisions of the Kyoto Protocol have been criticized by the United States and Australia, and were used as part of a rationale for non-ratification by the U.S.

Developing countries dependent upon agriculture will be particularly harmed by global warming.
The issue of climate change has sparked debate weighing the benefits of limiting industrial emissions of greenhouse gases against the costs that such changes will entail.

There has been discussion in several countries about the cost and benefits of adopting alternative energy sources in order to reduce carbon emissions. Business-centered organizations, conservative commentators, and large petroleum companies have downplayed IPCC climate change scenarios. They have also funded scientists who disagree with the scientific consensus, and provided their own projections of the economic cost of stricter controls. Likewise, environmental organizations and a number of public figures have emphasized the potential risks of climate change and promote the implementation of GHG emissions reduction measures.

Some fossil fuel companies have scaled back their efforts in recent years, or have called for policies to reduce global warming.

Another point of contention is the degree to which emerging economies such as India and China should be expected to constrain their emissions. According to recent reports, China's gross national CO2 emissions may now exceed those of the U.S. China has contended that it has less of an obligation to reduce emissions since its per capita emissions are roughly one-fifth that of the United States. India, also exempt from Kyoto restrictions and another of the biggest sources of industrial emissions, has made similar assertions. The U.S. contends that if it must bear the cost of reducing emissions, then China must as well.

Some arid and semi-arid lands can support crops, but additional pressure from greater populations or decreases in rainfall can lead to the few plants present disappearing. The soil becomes exposed to wind, causing soil particles to be deposited elsewhere. The top layer becomes eroded. With the removal of shade, rates of evaporation increase and salts become drawn up to the surface. This increases soil salinity and inhibits plant growth. The loss of plants causes less moisture to be retained in the area, which may change the climate pattern leading to lower rainfall.

A number of methods have been tried in order to reduce the rate of desertification and regain lost land; however, most measures treat symptoms of sand movement and do not address the root causes of land modification such as overgrazing, unsustainable farming (eg cattle farming) and deforestation by the indigenous population. In developing countries under threat of desertification, many local people use trees for firewood and cooking, which has increased the problem of land degradation and often even increased their poverty. In order to gain further supplies of fuel the local population add more pressure to the depleted forests; adding to the desertification process.

Techniques to counter desertification focus on two aspects: provisioning of water (eg by wells and energy intensive systems involving water pipes over long distances) and fixating and hyper-fertilizing soil.

Fixating the soil is often done through the use of shelter belts, woodlots and windbreaks. Windbreaks are made from trees and bushes and are used to reduce soil erosion and evapotranspiration.

The enriching of the soil and the restoration of its fertility is often done by a variety of plants. Of these, the Leguminous plants which extracts nitrogen from the air and fixes it in the soil, and food crops/trees as grains, barley, beans and dates are the most important.

Africa, with coordination from Senegal, has launched its own "green wall" project. Trees will be planted on a 15 km wide land strip from Senegal to Djibouti. Aside from countering desert progression, the project is also aimed at creating new economic activities, especially thanks to tree products such as gum arabic

More efficient use of existing water resources and control of salinization are other tools for mitigating arid lands. New ways are also being sought to find groundwater resources and to develop more effective ways of irrigating arid and semiarid lands. Research on the reclamation of deserts is also focusing on discovering proper crop rotation to protect fragile soil, on understanding how sand-fixing plants can be adapted to local environments, and on how overgrazing can be addressed.

A recent development is the Seawater Greenhouse and Seawater Forest. This proposal is to construct these devices on coastal deserts in order to create freshwater and grow food.

The Sahara Forest project will use seawater and solar power to grow food in greenhouses across the desert. Vast greenhouses that use seawater to grow crops could be combined with solar power plants to provide food, fresh water and clean energy in deserts, under an ambitious proposal from a team of architects and engineers.

The Sahara Forest project would marry huge greenhouses with concentrated solar power (CSP), which uses mirrors to focus the sun's rays and generate heat and electricity. The installations would turn deserts into lush patches of vegetation, according to its designers, and without the need to dig wells for fresh water, which has depleted acquifers in many parts of the world.

The current art is however unproven and of limited applicability, since sites must be chosen that are below sea level.
It is an objective of the current invention to provide a widely applicable and sustainable way of turning the Earth’s hot deserts into lush vegetation.

It is another objective of the current invention to create a method of mitigating the effects of global warming that are economically conducive to implementation.

As explained above the area of the Earth’s surface covered by the oceans is 361 million square kilometres. Furthermore it is assumed for the purposes of this invention that if the status quo is maintained sea levels will rise 480mm (.00048km) over the coming century. In order to maintain current sea levels, it would be necessary therefore for the purposes of the current invention (using this aspect alone) to sequester 173,280 km3 (361,000,000 km2  X .00048km) of desalinated water in the world’s hot deserts. As shown in Table 2 the hot deserts cover an area of 15,559,000 km2. Therefore .0111km or 173,280 km3/15,559,000 km2 of water will have to be taken up by the deserts the next hundred years or .111 m of water every year