Deserts and climate change

Deserts cover some 26.2 million square kilometers, or about 20 percent, of the Earth’s land surface, mainly in the subtropical to midlatitudes. The importance of water to human and natural systems in deserts makes those systems very sensitive to climate change, affecting the amount, type, timing, and effectiveness of precipitation.

Background

Deserts are fragile environments, easily affected by natural and human disturbance. They are being affected by a rapidly growing and increasingly urban population that is dependent on scarce surface and groundwater. The historical and observational record indicates the great natural variability of climates in these regions, including the occurrence of periodic severe and multi-decadal droughts.

Causes of Deserts

Desert climates are characterized by low humidity (except in cool, foggy coastal deserts such as the Namib and Atacama), a high daily range of temperatures, and precipitation that is highly variable in time and space. The most extensive deserts lie astride the tropics. Solar heating in equatorial latitudes gives rise to rising moist air, which then condenses, loses moisture as tropical rainfall, cools, and descends away from the equator. As the air descends, it warms and becomes very dry. This descending, dry air in the subtropical anticyclonic belts maintains arid conditions throughout the year. The effects of stable air masses are reinforced in some areas by mountain barriers, which block moist air masses (for example, the Himalaya and other mountain ranges prevent the penetration of the southwest monsoon to the Gobi and Takla Makan Deserts of central Asia). Deserts located on the west coasts of South America and southern Africa (the Atacama and Namib) owe their hyperarid climates to the influence of cold oceanic currents offshore. These currents reinforce the subsidence-induced stability of the atmosphere by cooling surface air and creating a strong temperature inversion.

Effects of Climate Change

The effects and potential effects of past and future climate change on deserts are many and are influenced by the topographic and climatic diversity of desert regions. Global climate models differ in their predictions of the direction and magnitude of future change in arid regions. In some areas—such as China, southeastern Arabia, and India—increased monsoon precipitation is predicted; however, its effects may be offset by higher evaporation resulting from increased temperatures. In the Sahara Desert, there is support in many climate-model predictions for increased rainfall in the southern and southeastern areas (including the Sahel), but strong drying in the northern and western areas. Some models, however, suggest a strong drying throughout the region.

The differences between various models’ predictions for the Sahara demonstrate the complexity of forcing factors in the region, as well as the possible influence of feedbacks between land-surface conditions and the atmosphere. Such feedback could affect rainfall total, effectiveness, and spatial distribution. Most of the interior of southern Africa is also predicted to become drier, leading to the mobilization of sand dunes in the Kalahari Desert, as well as severe impacts on surface and groundwater resources.

In the southwestern United States, higher temperatures are predicted to increase the severity of droughts. Some models indicate that the region may already be in transition to a new, more arid state as a result of anthropogenically influenced climate change. The economies of many desert regions (including Atacama, the American Southwest, Iran, western China, and southwest Asia) depend on runoff derived from winter snow in mountain areas for domestic use and irrigated agriculture. Higher temperatures are already reducing the amount of snowpack and changing the timing and duration of spring runoff. More precipitation is falling as rain, leading to less natural storage and an increased risk of flooding. Such changes, if continued, will require costly upgrades of water management systems and possibly a reduction in available water supply.

Many desert areas experienced significant increases in temperature and reductions in rainfall between 1980 to 2020. During that period, droughts occurred in the Colorado River Basin, Australia, Southern Africa, Iraq, Afghanistan, and more. With these droughts, the risk of wildfire increases, and in areas with invasive grasses, these fires are fueled, further altering the ecological landscape. Nearly 28 percent of the world's land surface became much more arid between 1960 and 2023, while over 20 percent became much less arid, according to a study published in Communications Earth and Environment.

Sand dunes occupy up to one-third of the area of many desert regions. Dune mobility is a function of the ratio between wind strength and effective rainfall and is measured by the dune mobility index. Increased temperatures, accompanied by decreased rainfall, are predicted to lead to remobilization of vegetated sand dunes in the Kalahari and drier areas of the Australian desert.

The effects of climate change on vegetation patterns in desert regions are difficult to separate from anthropogenic disturbance. Increased levels of atmospheric carbon dioxide (CO₂) may increase plant productivity in arid regions. Higher CO₂ levels may also favor invasive exotic species such as cheat grass, with adverse effects on fire regimes in the Great Basin Desert. Models that incorporate CO₂ fertilization of vegetation indicate a reduction in desert areas in the next century, introducing an additional level of uncertainty about the future of desert ecosystems.

During the 2020s, the advancement of global climate change caused significant problems in many desert communities. One of the most striking problems faced by these communities was a significant increase in the strength and frequency of sand and dust storms. To raise awareness of this issue, in 2023, the United Nations designated July 12 as the first International Day of Combating Sand and Dust Storms.

Context

The great natural variability of climatic conditions, especially the distribution of rainfall in space and time, presents challenges for predicting the response of desert regions to future climate change. However, the experience of drought episodes in the first decades of the twenty-first century indicates that the natural and human systems of deserts and desert margin areas are highly susceptible to soil moisture deficits. Climate change is expected to decrease water availability in all desert regions due to increased temperatures, changes in precipitation amounts, or a combination of both. The result will be increased pressure on existing water resources for human and ecosystem use, possibly leading to higher levels of conflict over scarce resources.

Key Concepts

• drought: an extended period of months or years during which a region experiences a deficit in its water supply, mainly as a result of low rainfall
• dune mobility index: a measure of potential sand mobility as a function of the ratio between the annual percentage of the time the wind is above the sand transport threshold and the effective annual rainfall
• subtropical anticyclonic belts: a series of high-pressure belts situated at latitudes 30° north and south of the equator

Bibliography

"As Climate Changes, Sand Storms Wreak Havoc on Desert Communities." UN, 11 July 2023, www.unep.org/news-and-stories/story/climate-changes-sand-storms-wreak-havoc-desert-communities. Accessed 29 Oct. 2025.

Bombi, Pierluigi, et al. “Climate Change Effects on Desert Ecosystems: A Case Study on the Keystone Species of the Namib Desert Welwitschia Mirabilis.” PloS One, vol. 16, no. 11, 2021, p. e0259767, doi:10.1371/journal.pone.0259767. Accessed 29 Oct. 2025.

Ezcurra, E., editor. Global Deserts Outlook. United Nations Environment Programme, 2006.

Goudie, A. S. Great Warm Deserts of the World: Landscapes and Evolution. Oxford UP, 2002.

Ma, Liang, et al. “Global Patterns of Climate Change Impacts on Desert Bird Communities.” Nature Communications, vol. 14, no. 1, 2023, doi:10.1038/s41467-023-35814-8. Accessed 29 Oct. 2025.

Saravia, Christian. "Desertification and Climate Change: What’s the Link?" Earth.org, 12 Feb. 2025, earth.org/desertification-and-climate-change-whats-the-link. Accessed 29 Oct. 2025.

Sardans, Jordi, et al. "Growing Aridity Poses Threats to Global Land Surface." Communications Earth & Environment, vol. 5, no. 1, 2024, doi:10.1038/s43247-024-01935-1. Accessed 29 Oct. 2025.