Valencia floods: warming climate is making once rare weather more common and more destructive, researchers say

In recent days, a seasonal weather system known in Spain as a “cold drop” or DANA (an acronym for “depresión aislada en niveles altos”: isolated cyclone at high level) has been causing heavy rain and flooding across Spain’s Mediterranean coast. causing flooding in Andalusia, especially in the Valencia region, Castile-La Mancha and the Balearic Islands. The storm left hundreds of people dead, many more missing, and caused extensive damage in the affected areas.

Fifty years ago, DANA occurred every three to four years, usually in November. Today they can occur all year round.

How is DANA formed?

These storms form in the same way as hurricanes in the Atlantic Ocean and typhoons in China. The difference is that the Mediterranean Sea is smaller than these regions, so storm paths are shorter and less energy and water vapor can be stored.

Decades ago, when the ocean surface warmed at the end of summer, water evaporated into the atmosphere. Currently, the sea surface is warm all year round, and large amounts of water vapor are constantly released into the atmosphere.

The polar regions are also much warmer now than they were 50 years ago. As a result, the polar jet stream (the airflow that surrounds the Earth at about 11,000 meters above sea level) weakens and becomes more meandering, similar to a slow-moving stream. These usually bring cold air from Greenland into the skies above Spain.

Evaporated water rising from the ocean meets this very cold air and condenses. The Earth’s rotation causes the updrafts to rotate counterclockwise, and the resulting condensation releases large amounts of water.

This combination of factors causes heavy rains to be concentrated in Spain, particularly in the Balearic Islands and the Mediterranean coast, sometimes reaching inland areas such as the Sierra de Segura Mountains in Andalusia, Castile-La Mancha and the Cuenca Mountains in Aragon. Sometimes. These storms can move very quickly and are very intense.

Sometimes this Mediterranean water vapor travels all the way to the Alps and beyond its western edge, causing heavy rains in central Europe.

Ocean warming, polar warming

Many years ago, humans discovered a huge source of energy. That’s 30 million years’ worth of solar energy stored underground by plants and animals. Currently, we are rapidly depleting this resource.

This fossil energy source consists of carbon compounds such as coal, hydrocarbons, and natural gas. Burning them releases polyatomic molecules such as carbon dioxide, methane, nitrogen oxides, and other compounds. Once released into the atmosphere, these capture some of the heat radiating from the Earth’s soil and oceans and return it to the Earth’s surface.

This process is what causes climate change and can occur naturally. When these molecules, especially methane, accumulate on continental ocean slopes, they cool the water and trap carbon dioxide captured by waves in the ocean. As the Earth cools and sea levels fall, methane will eventually be released into the atmosphere. The warming atmosphere warms the oceans, which release carbon dioxide and amplify the effects of methane. After that, the Earth becomes warmer and warmer, glaciers melt and sea levels rise.

This alternation between cold and hot has occurred eight times in the past million years.

No end in sight for fossil fuels

Today we force this process by releasing large amounts of polyatomic gases ourselves. The question is whether these emissions can be limited. So far this has not been possible.

Add to this the fact that by 2050 there will be around 2 billion more humans on the planet, who will also need food, shelter and transportation. This means more chemical fertilizers, cement, gasoline, diesel and natural gas are consumed, leading to the release of further polyatomic gases.

Various measures to limit the combustion of carbon compounds are insufficient or very underdeveloped. For example, expectations for electric cars have waned significantly in recent years.

Although solar and wind energy are being developed in Europe, electricity only accounts for about a third of the energy consumed. Europe is also the only region that has made substantial progress in alternative power generation. Much of China’s progress has been offset by continued construction of coal-fired power plants.

Despite some large-scale, high-profile projects, the reality is that we will continue to burn carbon compounds for decades to come. This means that the concentration of polyatomic gases in the atmosphere will increase over the next century, leading to a corresponding rise in global temperatures and an increase in DANA, hurricanes, typhoons, and floods.

Climate adaptation is essential

What we are left with is adaptation, which is much more manageable because it does not require international agreements.

In Spain, for example, floods can be controlled through rainwater harvesting systems that include large-scale tree planting in inland mountainous regions and the construction of small wetlands and reservoirs on hillsides. This would slow the amount of water reaching the Las Ramblas and Barrancos, the canyons and canals that channel rainwater into Spanish towns and prevent flooding. At the same time, this means that water is drawn into the soil and gradually returns to rivers and reservoirs.

This is not only possible, it is cost-effective, creates many jobs, and has the potential to save hundreds, if not thousands, of lives.

This article is republished from The Conversation under a Creative Commons license. Read the original article.