In recent days, a seasonal weather system known in Spain as the “cold drop” or DANA (an acronym for depression is carried out in the heights of Nivelles: isolated depression at high levels) has caused heavy rainfall and flooding along Spain’s Mediterranean coast and in Andalusia, especially in the Valencian Community, Castile-La Mancha and the Balearic Islands. The storm left hundreds dead and many more missing, causing massive damage in the affected areas.
50 years ago, a DANA took place every three or four years, usually in November. Nowadays they can occur all year round.
How is a DANA created?
These storms form similarly to Atlantic hurricanes or typhoons in China. The difference is that the Mediterranean Sea is smaller than these areas, so storms travel a shorter path and store less energy and water vapor.
Decades ago, warm sea surfaces at the end of summer caused water in the atmosphere to evaporate. Today, the sea surface is warm all year round, continuously sending enormous amounts of water vapor into the atmosphere.
The poles are also much warmer now than 50 years ago. As a result, the polar jet stream – the air current that surrounds the Earth at about 11,000 meters above sea level – weakens and, like any slow-flowing current, becomes meandering. These bring cold air, mostly from Greenland, into the high atmosphere above Spain.
The evaporated water rising from the sea meets this very cold air and condenses. The Earth’s rotation causes the rising air to spin counterclockwise, and the resulting condensation releases enormous amounts of water.
This combination of factors causes heavy, concentrated rainfall to fall in Spain, particularly on the Balearic Islands and the Mediterranean coast, sometimes reaching as far inland as the Sierra de Segura mountains in Andalusia and the Serrania de Cuenca mountains in Castilla la Mancha and Aragon. These storms can occur very quickly and are extremely violent.
Occasionally, this Mediterranean water vapor has traveled as far as the Alps, crossing the western tip and causing downpours in central Europe.
Warming oceans, warming poles
Many years ago, people discovered a gigantic energy source: 30 million years of solar energy, stored underground by plants and animals. Today we are quickly burning this resource.
This fossilized energy source consists of carbon compounds: 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 seas and return it to the Earth’s surface.
This process is the cause of climate change, and it can occur naturally. When these molecules, especially methane, are stored on the slopes of the continental ocean, the water cools and the carbon dioxide captured by the waves is trapped inside. As the planet cools and sea levels drop, methane eventually enters the atmosphere. The atmosphere warms, causing the sea to warm, and the sea emits CO₂, which increases the effect of methane. The planet then becomes increasingly warmer, causing glaciers to melt and sea levels to rise.
This alternation of cold and warm has occurred eight times in the past million years.
There is no end in sight for fossil fuels
Today we force this process by emitting enormous amounts of polyatomic gases ourselves. The question is whether we can limit these emissions. So far this has proven impossible.
To this we can add the fact that by 2050 there will be approximately two billion more people on the planet, who will also need food, housing and transportation. This means that more fertilizer, cement, gasoline, diesel and natural gas will be consumed, releasing even more polyatomic gases.
Various measures to limit the combustion of carbon compounds are inadequate or develop very slowly. For example, hopes for electric cars have diminished sharply in recent years.
Europe is making progress in solar and wind energy, but electricity only accounts for about a third of the energy consumed. Europe is also the only region making real progress in alternative electricity generation – much of China’s progress is being offset by the continued construction of coal-fired power stations.
Despite some large, high-profile projects, the reality is that we will continue to burn carbon compounds for many decades to come. This means that the concentration of polyatomic gases in the atmosphere will increase over the next century, and with it the temperature of the planet, leading to more DANAs, hurricanes, typhoons and floods.
Climate adaptation is essential
What we are left with is adjustment, which is much more manageable because it does not require international agreements.
In Spain, for example, we can control flooding through massive reforestation in inland mountainous areas, and through rainwater harvesting systems, which build small wetlands or reservoirs on slopes. This would slow down the amount of water reaching the Ramblas barrancosthe gorges and canals that channel rainwater through Spain’s cities and prevent them from flooding. At the same time, this would mean that water could be captured by the soil and gradually returned to rivers and reservoirs.
Not only is this feasible, it is also cost-effective, generates many jobs and could save hundreds, if not thousands, of lives.
This article was originally published in The Conversation, a post dedicated to comparing ideas from academic experts.
Lee mas:
Antonio Ruiz de Elvira does not receive any salary, he does not work as a consultant, he does not propose any business, he does not receive financing from any company or organization that could benefit from this article, and has declared that he takes care of relevant relevant issues across the academic world.
