In Spain we have spent about six months without rain and suddenly, within two weeks, we have had more flooding than the weather records mark.
The problem is not intensity. In the ephemeris of the last centuries we can find intense phenomena from time to time, but generally isolated in time and space.
Today extreme phenomena are repeated every bit and spread to large geographical areas. Not just in Spain, obviously, but all over the globe. For example, fires in California.
With regard to the recent floods in Spain, the cause is clear. An excess of water vapour embalmed between the coastal chains of the Atlas Mountains in Africa and the Spanish mountains, and sudden invasions of cold air.
Map of the air currents circulating on the planet. | Author providedOn the planet constantly circulates an intense current of air, about 10 km high, produced by the difference in temperatures between the equator and the Pole. It pushes the air from south to north and Coriolis’ acceleration diverts it eastwards.
The maximum intensity of this air jet, the polar jet, is located above the point of maximum temperature gradient. In winter, with the pole very cold, it used to be over Morocco. In summer, about the Cantabrian.
Today, human-caused climate change, the fastest since the Earth’s existence, has warmed the North Pole. The maximum gradient has shifted northward, and in summer it is located above the latitude of York, in England.
The cold air jet doesn’t circulate much over Spain from May to November, and hence the droughts.
As the temperature gap between the equator and the North Pole decreases, the river of air, like a river of water reaching the plain, begins to make large meanders. When one of these is placed over Spain, it injects very cold air in height and, at that moment, the vortices that leave intense rains begin to be produced.
Cold air in height sucks in hot air filled with water vapour. Again The acceleration of Coriolis causes the air, when it rises, to form a vortex, a whirlwind that self-feeds as long as there is hot water down and cold air above: a minihurricane.
We had one of these polar jet meanders 15 days ago. It was then that in Arganda del Rey, in Madrid, a vertical meter of hail accumulated. We’ve had another intense meander since 9/11. It has produced flooding in Murcia (where the Segura is channeled and usually empty) as there has not been since the nineteenth century (when the river did not go between walls).
We keep burning carbon through full hands. Solar power doesn’t take off.
The easiest and safest prediction is that every year that passes we will have increasingly extreme phenomena.
Antonio Ruiz de Elvira Serra, Catedratico of University of Applied Physics, University of Alcalá
This article was originally published in The Conversation. Read the original.