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The dry spell that affected Europe during the summer of 2022 was particularly severe, leading to significant soil desiccation in various areas. Public debates often referenced how much climate change may have worsened this intense weather phenomenon. A research team has now revealed that over 30 percent of the unusual intensity and geographical spread of the drought is linked to climate change caused by human actions. As noted in their publication in Nature Geoscience, the situation was aggravated because climate change had already led to a steady decline in soil moisture over the years preceding the drought.
The dry spell that impacted Europe during the summer of 2022 was particularly severe, resulting in significant soil desiccation in many areas. Public discussions frequently raised the issue of how much climate change may have intensified this extreme weather phenomenon. A research team led by the Helmholtz Centre for Environmental Research (UFZ) has found that over 30 percent of the remarkable intensity and reach of the drought can be linked to climate change driven by human actions. In an article in Nature Geoscience, they highlight that this extreme situation was worsened by the continuous decline in soil moisture levels due to climate change in preceding years.
The extreme drought notably disrupted public life across many countries in Central and Southern Europe from June to August 2022. For example, approximately half the Italian population experienced water restrictions, and in France, over 100 areas relied on trucked water for drinking. Agricultural output saw a decline of 15 percent for crops like grain maize, sunflower, and soybean when compared to averages from 2017 to 2021. Severe wildfires erupted in nations including Italy, France, Slovenia, and Romania, and river navigation, particularly on the Po and Rhine, faced limitations as hydroelectric facilities saw diminished output attributed to lower water flow. According to Dr. Emanuele Bevacqua, the principal author of the study and leader of the UFZ working group on Compound Climate Extremes, “The summer drought in 2022 had significant socio-economic repercussions for Europe.”
The Intergovernmental Panel on Climate Change (IPCC) previously acknowledged that droughts are influenced by human-made climate change. Nevertheless, our understanding of how climate change affects specific drought incidents has been limited. To examine soil water storage and its geographical distribution, alongside river discharge volumes in Europe, the research team employed observational data in conjunction with the mHM hydrological model designed at UFZ, which integrates precipitation and temperature measurements.
During their analysis, the researchers estimated that the shortfall in soil moisture within the top two meters across Central and Southern Europe from June to August was around 280 cubic kilometers. This translates to a water volume comparable to that of 120 million swimming pools. Additionally, approximately 1.64 million square kilometers were impacted by drought during this period, representing about 29 percent of the land in Central and Southern Europe, a figure not seen since 1960. “Our simulations indicate that the 2022 drought was the most severe since 1960,” states Emanuele Bevacqua. The amount of water in the soil reached its lowest level since the beginning of satellite monitoring in 2002. The unprecedented seriousness of the drought resulted predominantly from unusual weather conditions: significant parts of Europe received little to no precipitation from March to August. Heatwaves further led to an exceptionally warm summer, with average temperatures in Central and Southern Europe being 1.9 degrees Celsius higher than the norm from 1981 to 2010. “While reduced precipitation was a key factor in the drought, elevated temperatures further exacerbated the dwindling soil moisture and runoff,” explains the UFZ researcher.
The research team also analyzed how human-induced climate change contributed to the extreme drought of summer 2022. They compared real soil moisture levels with those that would have occurred without the effects of climate change on precipitation and temperature. Ultimately, it was found that of the estimated soil moisture deficit of about 280 cubic kilometers in Central and Southern Europe, roughly 87 cubic kilometers, amounting to 31 percent, can be linked to climate change. This change also significantly affected the spatial distribution of the drought: approximately 38 percent, or 0.61 million square kilometers of the drought-impacted area in Europe, can be attributed to climate change. “Climate change has greatly aggravated the drought conditions, primarily due to the elevated temperatures that increase evaporation rates,” notes Prof. Dr. Jakob Zscheischler, co-author and head of the UFZ’s Department of Compound Environmental Risks. Furthermore, climate change influences water flow levels in rivers, affecting navigation and hydroelectric energy production, with climate change contributing to 19 percent of the areas where rivers in Central and Southern Europe were dry.
The researchers also provided a more detailed assessment of the impact of climate change on the extreme drought conditions experienced in the summer of 2022. “The rise in temperatures due to human-caused climate change is not a sudden occurrence; it has been built into the system over an extended period,” explains UFZ climate scientist Jakob Zscheischler. For instance, the water management year of 2021/2022 started in November 2021 with lower soil moisture and discharge levels that would not have happened without climate change influences. The researchers were able to measure this factor more accurately, noting that the impact of climate change on drought intensity manifests over time. They quantified the previous contribution of climate change to the 2022 drought, revealing a lagged effect that made up between 14 to 41 percent of the total climate change contribution, depending on the hydrological model employed. “In recent years, climate change has consistently led to rising temperatures and increased evaporation, substantially influencing the drought conditions of summer 2022,” explains Jakob Zscheischler. Emanuele Bevacqua adds, “The delayed effects of climate change on droughts have received insufficient attention thus far.” However, this aspect is crucial, as approximately two-thirds of Europe’s population relies on groundwater, which is already being over-exploited in numerous cities.
The extreme drought severely affected public life in many countries in Central and Southern Europe between June and August in the summer of 2022. For example, half the population in Italy faced water restrictions, while in France more than 100 municipalities were supplied with drinking water via trucks. In agriculture, grain maize, sunflower, and soybean yields across Europe dropped by 15 percent compared to the average over 2017 to 2021. Severe forest fires raged in Italy, France, Slovenia, and Romania, navigation was restricted on rivers such as the Po and Rhine and hydroelectric power plants produced less electric power due to the lower discharge. “The summer drought in 2022 had serious socio-economic consequences for Europe,” says Dr. Emanuele Bevacqua, lead author of the study and head of the UFZ working group Compound Climate Extremes.
The Intergovernmental Panel on Climate Change (IPCC) had already established that droughts
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Human-caused climate change is impacting various regions, but our knowledge about how it specifically contributes to individual drought incidents is still developing. In order to explore water storage capacities in soil and their geographical variations, along with river discharge levels in Europe, researchers utilized observational data paired with the mHM hydrological model from the UFZ, which incorporates data on precipitation and temperature.
The researchers discovered a simulated soil moisture shortfall of approximately 280 cubic kilometers in the upper two meters of soil across central and southern Europe from June to August. This translates to a water volume missing that is equivalent to about 120 million swimming pools. Additionally, around 1.64 million square kilometers experienced drought conditions during this period, representing nearly 29 percent of the land in Central and Southern Europe—marking the largest affected area since 1960. “Our simulations indicate that the 2022 drought was the most severe since 1960,” states Emanuele Bevacqua. The ground water levels recorded were the lowest since satellite observations began in 2002. The unprecedented intensity of the drought was largely attributed to unusual weather patterns, with extensive areas of Europe receiving minimal rainfall from March to August. Heatwaves also played a role, resulting in exceptionally high summer temperatures. Average summer temperatures in Central and Southern Europe were 1.9 degrees Celsius higher than the average from 1981 to 2010. “While the lack of precipitation was a critical factor for the drought, elevated temperatures exacerbated the decrease in soil moisture and river runoff,” explains the researcher from UFZ.
The research team next assessed how much human-driven climate change caused the extreme drought experienced in the summer of 2022. They performed this analysis by comparing observed soil moisture levels under actual weather conditions to those measured without taking climate change effects on rainfall and temperatures into account. Their findings indicate that out of the estimated soil moisture deficit of around 280 cubic kilometers in Central and Southern Europe, roughly 87 cubic kilometers—or about 31 percent—can be linked to climate change. Moreover, climate change significantly influenced the geographical scope of the drought, contributing to about 38 percent or 0.61 million square kilometers of the drought-affected landscape in Europe. “Climate change has notably heightened the severity of the drought, primarily due to increased temperatures, which amplify evaporation rates,” comments Prof. Dr. Jakob Zscheischler, a co-author and head of the UFZ’s Department of Compound Environmental Risks. Additionally, climate change affects the volume of water reaching rivers, thereby impacting navigability and hydropower utilization. For instance, climate change played a role in 19 percent of the regions experiencing dry riverbeds in Central and Southern Europe.
The researchers delved deeper into quantifying the impact of climate change on the intense drought of summer 2022. “The rise in temperatures linked to human activity is a gradual process, having been embedded in our climate systems over time,” explains Jakob Zscheischler, a climate scientist at UFZ. The water management year of 2021/2022 kicked off in November 2021 with lower soil moisture and river discharge levels that would likely not have occurred without anthropogenic climate influence. The researchers successfully quantified this aspect, revealing how the effects of climate change on drought intensity unfold over time. They found that the influence of climate change that was already “stored” in the system before November 1, 2021, contributed between 14 and 41 percent of the overall climate change impact, depending on the specific hydrological model used. “Over the years, climate change has steadily led to higher temperatures, increased evaporation, and drying of soils, thus playing a significant role in the summer drought of 2022,” asserts Jakob Zscheischler. Emanuele Bevacqua further emphasizes, “The delayed effects of climate change on droughts have not received adequate attention so far.” Recognizing this factor is crucial since groundwater supplies vital water needs for about two-thirds of Europe’s population, and many urban areas are already facing groundwater depletion issues.
