Reviewed by Alex SmithMay 17 2022
The drought that took place from 2018 to 2020 were the days, months and years that many people will recollect. An international research group headed by researchers from the Helmholtz Centre for Environmental Research (UFZ) has been successful in classifying the historical dimensions of this event.
Image Credit: Helmholtz Center for Environmental Research.
Relying on their outcomes, no drought covering the huge area for an extended period and agreeing with warmer temperatures has happened in Europe since the middle of the 18th century.
Hence, the years from 2018 to 2020 depict a new benchmark for droughts. Since such an event can take place more frequently in the future, scientists recommend the development and implementation of appropriate, regionally adapted drought prevention efforts.
Shriveled meadows and fields, dead forests, dry stream beds, and decreased power plant outputs — the drought years of 2018, 2019 and 2020 were unusual and had considerable effects on nature and the economy. Previously, however, it was not evident where they must be categorized in their historical dimension.
“The 2018 to 2020 drought sets a new benchmark for droughts in Europe”, says Dr. Oldrich Rakovec, UFZ modeler and lead author of the article reported in the Earth’s Future journal of the American Geophysical Union.
This was documented by the researchers with a huge compilation of data and modeling methods which enabled them to rebuild historical droughts back to 1766 and make a comparison of their extents with the drought of 2018 to 2020.
The drought that happened from 2018 to 2020 thus impacted around one-third of the land area of Europe, particularly in central Europe, like France, Germany and the Czech Republic.
No other drought event over the last 250 years had such a large spatial extent as this one.
Oldrich Rakovec, Study Lead Author, Helmholtz Centre for Environmental Research
Also, the complete duration of the drought event in Europe was exceptionally long, starting in April 2018 and not ending until December 2020: 33 months. The drought between 1857 and 1860 continued slightly longer for a total of 35 months. What’s more: The drought from 2018 to 2020 also continued in 2021 and 2022 in deeper soils (that is., up to 2 m below the ground surface).
Although 2021 was wetter and supplied much needed water in the upper soil important for sustaining agriculture activities, the moisture did not penetrate to greater depths.
Oldrich Rakovec, Study Lead Author, Helmholtz Centre for Environmental Research
The average drought duration was exceptionally long in the 50 × 50 km grid cells in which the researchers partitioned Europe for their modeling activity.
As a drought event develops in a dynamic manner in space and time (that is, it begins at one point, then continues developing, and ultimately ends somewhere else) the mean duration alters from its total one. In this case, the 2018–2020 event displayed a mean drought duration of 12 months.
In the past, the drought event that happened from 1857 to 1860 lasted longer, with a mean duration of 13 months. The scientists specify drought as the time in which the present soil-water content in the top 2 m of soil falls beneath the level that has been achieved only 20% of the time during the 250 years.
To rebuild such historical droughts, the researchers utilized the mHM hydrologic model developed at the UFZ. Amongst other things, this environmental model could be utilized to evaluate soil moisture content depending on precipitation records and past temperature.
Also, the increase in air temperature obtained a historical record at the time of the 2018–2020 drought event. This has an anomaly of 2.8 °C above the long-term average for the past 250 years.
The droughts in the past were colder than recent droughts in which the average temperature hardly changed.
Dr. Rohini Kumar, Study Co-Author and Modeler, Helmholtz Centre for Environmental Research
The impacts of a drought event become considerably more severe if, besides the precipitation deficit (around 20% for major drought events in the past centuries), the warmer conditions prevail. This integrated effect leads to higher evaporation losses, thereby resulting in decreasing soil-water levels.
Also, the researchers analyzed the impacts of the lack of water for agriculture at the time of this drought event. They made a comparison of the average annual crop yields for grain maize, wheat and barley between 2018 and 2020 with those between 1961 and 2021.
The outcomes denote those harvests were considerably decreased in countries impacted mostly by the 2018–2020 drought. For instance, grain maize production reduced by between 20 and 40% in the Benelux countries, Germany and France; wheat reduced by up to 17.5% in Germany, and barley reduced by 10% in almost all of Europe.
Furthermore, how droughts will develop in Europe in the future relies on the severity of global warming.
The researchers modeled the extent and duration of droughts for two representative concentration pathways (RCPs), explaining if the future greenhouse gas emission scenarios will be highly moderate (RCP4.5) or will continue unimpeded (RCP8.5) up to the year 2100.
The researchers identified that the mean drought duration increases considerably to up to 100 months for an RCP4.5 scenario, while the drought areal extent is projected to rise, thereby covering up to 50% of Europe’s region.
The situation is kind of different for the extreme RCP8.5 scenario: In this instance, the mean drought duration could be over 200 months, and the areal extent could impact up to 70% of Europe.
"Decision-makers should be prepared for significantly more severe drought events in future. Especially for devising new agricultural policies, this should be considered as a wake-up call to assess suitable measures to mitigate the threatening lack of water,” stated Dr. Luis Samaniego, co-author of the article and Head of the Stochastic and Land Surface Hydrology Working Group at the UFZ.
On a regional basis, this could be considered as the establishment of huge water reservoirs, like underground storage systems; breeding of more heat-resistant cultivars, or intelligent and smart irrigation technologies.
Journal Reference:
Rakovec, O., et al. (2022) The 2018–2020 Multi-Year Drought Sets a New Benchmark in Europe. Earth’s Future. doi.org/10.1029/2021EF002394.