DANA, which since Tuesday has caused more than 200 deaths and multiple destructions in the Valencian Community and other regions of Spain, has the stamp of climate change.
This is reflected in a first emergency analysis of the World weather attribution (WWA), a reference group supported by the global scientific community to study the contribution of climate change to an extreme event like DANA.
On October 31, scientists from the World Weather Attribution group (which includes experts from the National Meteorological and Hydrological Services) published a paper titled Ten years spent quickly elucidating the causes of extreme weather disasters.
Rains 12% more intense
The article explains how the science of attribution has advanced enough to analyze the role of climate change in individual phenomena. And the conclusions are devastating, such as the effect of DANA on Spanish territory, with a Mediterranean Sea warmer than normal, which generates more humidity and which gives more water load to these phenomena which become extreme.
In a quick analysis of Spain, the group It is estimated that precipitation was about 12% more abundant and twice as likely compared to the pre-industrial climate.with a temperature 1.3°C colder. The results agree well with previous attribution studies of heavy precipitation in Europe, such as storms Daniel and Boris.
A year’s rain in 8 hours
DANA left records of precipitation up to 500 mm in Valence and very notable in other regions of Spain, with the Valencia region being the most affected, with over 300 l/m² in many places.
Note that on October 29 and 30, the Chiva weather station (Valencia) received 491 l/m² in just eight hours, the equivalent of a year of rain, according to AEMET (State Meteorological Agency).
The WWA’s conclusion is that torrential rains were 12% more intense and twice as likely compared to the pre-industrial climate, that is to say on a planet 1.3°C cooler.
warm atmosphere
The analysis, reflected by the World Meteorological Organization (WMO), clearly indicates that “the climate change “This is the most likely explanation, since a warmer atmosphere can hold more moisture, causing heavy downpours.”
They warn that historical weather observations indicate that a day of torrential rains in the Valencia region, andincrease as fossil fuel emissions warm the climate“.
The WWA highlights the Clausius-Clapeyron relationship stating that “a warmer atmosphere can hold more water vaporleading to more intense precipitation (around 7% for every 1°C of global warming).
Flood disasters
From the WMO it is stated that “these record rains and flash floods that hit Spain, causing dozens of victims and enormous economic disruption and loss, is the latest in a series of catastrophic floods that have affected communities across the world. »
“This shows why the top priority of the WMO community is tosaving lives as climate change worsens extreme weather events», Underlines the meteorological organization.
The role of climate change
According to the Intergovernmental Panel on Climate Change, extreme weather events High-impact floods and droughts have become more likely and more severe due to anthropogenic climate change, and this has been confirmed by repeated events.
“Due to rising temperatures, the hydrological cycle has accelerated. It also became more erratic And unpredictableand we face growing problems of excess or shortage of water. A warmer atmosphere retains more moisture, which favors intense rainfall,” said WMO Secretary-General Celeste Saulo.
A very humid Mediterranean
The DANA phenomenon that affected Spain usually occurs in autumn, since The remaining surface heat from summer is offset by a sudden invasion of cold from the polar regions.. This gives rise to what meteorologists call “cutting system», with depression values which persist for several days and rotate over the region in question.
“The presence of warm air near the surface, fueled by excessive humidity from the Mediterranean Seastill hot, and the instability generated by the conflict with the cold air in the upper atmosphere, gives rise to large convective clouds with heavy rains and flash floods”, explains Omar Baddour, responsible for climate monitoring at WMO.
A phenomenon that will grow
“It is expected that the climate change is intensifying these systems due to warming of marine waters and increased humidity in the atmosphere,” Baddour explains.
For every degree Celsius of warming, saturated air contains on average 7% more water vapor. SO, each additional fraction of warming increases atmospheric moisture contentwhich increases the risk of extreme precipitation.
More intense events
World Weather Attribution scientists published further studies that found that Climate change has increased the intensity of precipitation such as DANA and the impact of catastrophic flooding. in the Sahel and West Africa, East Africa, Asia (Nepal, India, Pakistan and Afghanistan) and southern Brazil this year.
However, studies have found that many other factors, including urbanization, land and water management and povertyalso played a role in some disasters.
The WMO report on the state of the global climate 2024, which will be published on the COP29 UN climate change negotiations in Baku, Azerbaijan, will present details on some of this year’s worst extreme events and their impacts.
