Mediterranean climate
A Mediterranean climate is defined by distinct wet winters and dry summers, with mild winter and hot summer temperatures. This climate type covers just under 2% of Earth's land area and is predominantly found in regions near large bodies of water, particularly the Mediterranean Sea and its surrounding areas. Characterized by stable high-pressure systems during the summer that prevent storm activity, these climates experience a significant drop in rainfall during the hotter months. The proximity to water moderates temperature fluctuations, preventing winter extremes and contributing to unique ecological systems.
Regions with a Mediterranean climate include coastal areas of central and southern California, parts of Australia, central Chile, and the western Cape of South Africa, alongside the Mediterranean basin itself. Climate change poses a significant threat to these regions, potentially altering their specific atmospheric conditions and leading to loss of biodiversity, as many species struggle to adapt to increasing temperatures and declining rainfall. Notably, areas in the Iberian Peninsula face challenges with desertification and rising heat stress, impacting both flora and fauna. As climate patterns shift, there is potential for Mediterranean climates to migrate, but existing ecosystems may be severely impacted, especially where movement to new areas is not possible.
Subject Terms
Mediterranean climate
Definition
Climate is the long-term average weather of a particular location. A Mediterranean climate is characterized by wet winters and dry summers, with mild winter and hot summer temperatures. This type of climate covers just under 2 percent of Earth’s land area. It is found only in the middle latitudes (around 35° to 45° north or south latitude) and near an ocean or the Mediterranean Sea. Most of the area included in this climatic zone is the Mediterranean Sea basin, for which it was named. Other Mediterranean climate regions include the coastal regions of central and southern California, central Chile, the west side of the tip of South Africa, and parts of southern Australia, particularly the southwest.
The summer dryness in Mediterranean climates is caused by stable atmospheric high-pressure systems preventing storm systems from entering the area. These semipermanent high-pressure systems move away from the area and toward the equator during the fall, allowing rain-producing low-pressure systems to move in. When high pressure is reestablished in the spring, low-pressure areas can no longer move through the area, and rain-free conditions are reestablished for a number of months.
Because this climatic zone is always near a large body of water and such water bodies moderate temperatures (water heats and cools more slowly than does land), Mediterranean winter temperatures rarely reach the freezing point. Summer temperatures are greatly affected by the relative warmth or coolness of the body of water adjoining the area. The Mediterranean Sea is a warm body of water, causing the Mediterranean basin to be relatively warm in the summer. Other areas, such as California, have relatively cool summer temperatures near the coast, because the Pacific Ocean, for example, is cooler than the Mediterranean Sea. The dryness of summer allows large temperature fluctuations during the day/night cycle. It also contributes to Mediterranean areas experiencing a relatively large number of wildfires, both because the air contains less moisture to resist fire and because the vegetation native to dry areas is itself drier and more prone to burn than that of wetter climates.
Significance for Climate Change
Mediterranean climates depend for their stability upon a combination of specific atmospheric conditions and the presence of a large body of water. Thus, if the atmospheric conditions are altered by climate change, or if they cease to exist near large bodies of water, Mediterranean climates will disappear. On the other hand, new Mediterranean climates could be established near different water bodies under the right circumstances.
Areas such as California or Chile are on north-south coastlines, and it is possible that climate change could move the climatic zone farther north or south. If the change is not overly abrupt, Mediterranean flora and fauna could migrate along with the climate zone. However, in the Mediterranean basin, a substantial increase in global warming or another climatic change could destroy the ecosystem altogether, because there is no large body of water to the north to which the climate, flora, and fauna could shift. Within Europe, there could be some movement north, as seems to be taking place in the British Isles. The little egret, commonly found in the Mediterranean Sea area, was unknown in England prior to 1996. As southern England began to develop a more Mediterranean climate, the little egret became the second most populous heron in the United Kingdom by 2008. In 2022, there were an estimated 660 to 740 breeding pairs of little egrets in the United Kingdom. However, those numbers increased to 4,500 birds during the winter months. While birds have the ability to move from the European mainland to Great Britain, however, plants and land animals do not.
Climatic changes have been documented in several Mediterranean and nearby regions. These changes raise particular concerns regarding biodiversity, which is more affected by climate than by other environmental factors. The Iberian Peninsula, for example, has the greatest animal diversity of any region in Europe, and many Iberian species are endangered by global warming. Average summer temperatures in the region are generally rising, which is putting a substantial heat stress upon both plants and animals. Humans are not immune to such factors, and a study documenting a 200 percent increase in the number of extremely hot days on the peninsula concluded that frail people’s lives were at risk from the increase.
Desertification is also taking place in the Mediterranean, as rainfall decreases and higher temperatures increase the rate of evaporation. A large number of droughts in the twenty-first century have contributed to the encroachment of the desert from the south. In the first months of 2022, a severe drought affected the western Euro-Mediterranean region. The lack of precipitation in the Iberian Peninsula extended from the last months of 2021 into the new year, causing dry conditions. A lack of rain continued into 2024, causing critical drought conditions, especially in Malta, southern Italy, and southern Spain. Also severely affected were Sicily, Morocco, and Spain. The drought continued into February, when a drought emergency was implemented with severe water restrictions.
It is estimated that up to 20 percent of plant species live in Mediterranean regions. In some areas, such as California, population growth has played a major factor in decreasing the number and diversity of plants, but changes in the precipitation patterns have also been a contributing factor, as has the resulting increase in wildfires. Even in areas where climate change has not substantially altered the total rainfall, the number of days on which it rains has changed. Many areas have fewer but harder rains than normal, resulting in less moisture being absorbed by the soil. An Intergovernmental Panel on Climate Change study has indicated that Mediterranean climates will very probably experience an increase in severe droughts, heat waves, and wildfires as a result of the changing climate.
Bibliography
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