Climate crisis the reason for Northern Hemisphere drought: study

Up until a little over a month ago, Europe was facing its worst drought in at least 500 years. 

About two-thirds of the continent was in a state of alert or warning, with a European Union agency noting reduced inland shipping, electricity production and the yields of certain crops.

The intensity of the crisis could be gauged from the numbers released by the European Drought Observatory, which said 47 percent of Europe was under warning conditions, with a clear deficit of soil moisture, and 17 percent in a state of alert, in which vegetation was affected.

A new report published by an international team of leading climate scientists as part of the World Weather Attribution group last evening revealed high temperatures that dried out soils across large parts of the Northern Hemisphere this summer were fueled by climate crisis.

World Weather Attribution is an international collaboration that analyses and communicates the possible influence of climate crisis on extreme weather events, such as storms, extreme rainfall, heatwaves, cold spells and droughts.

Their study estimated that human-caused climate crisis made soil moisture drought conditions at least 20 times more likely, threatening crop production and adding further pressure to food prices and food security.

“Our analysis shows that severe drought conditions across large parts of the Northern Hemisphere were fueled by human-induced climate change,” Dominik Schumacher, researcher at the Institute for Atmospheric and Climate Science at ETH Zurich, said.

“This result also gives us an insight on what is looming ahead. With further global warming we can expect stronger and more frequent summer droughts in the future.” 

This year’s summer in the Northern Hemisphere was one of the hottest ever recorded in Europe with over 24,000 heat-related fatalities. It was also very dry, and the resulting drought caused widespread water shortages, wildfires and crop failures leading to higher food prices, as well as impacts on electricity supply.

To quantify the effect of human-caused climate crisis on soil moisture deficits, scientists analysed weather data and computer simulations to compare the climate as it is today, after about 1.2 degrees of global warming since the late 1800s, with the climate of the past, following peer-reviewed methods.

The study analysed soil moisture levels across the entire Northern Hemisphere in the months of June, July and August 2022, excluding the tropics. 

Its focus, however, was limited to the Western and Central European region — extending from the Atlantic to the eastern Black Sea, between the Mediterranean and the Baltic — that experienced particularly severe drought with substantially reduced crop yields.

The researchers analysed moisture levels both for the top seven centimetre of soil and for the top 100 centimetre. The top metre – known as the root zone – is particularly important for crops as it is where plants extract water. 

Soil moisture dryness in this region of the soil is often referred to as agricultural and ecological drought.

The researchers found climate crisis made soil moisture droughts more likely across the extratropical Northern Hemisphere, both at the surface level and in the root zone, further stressing that climatic changes made the surface drought at least five times more likely and the agricultural and ecological drought at least 20 times more likely.

“The 2022 summer has shown how human-induced climate change is increasing the risks of agricultural and ecological droughts in densely populated and cultivated regions of the North Hemisphere,” Sonia Seneviratne, professor at the Institute for Atmospheric and Climate Science at ETH Zurich and coordinating lead author of IPCC Sixth Assessment Report, said.

“We need to phase-out the burning of fossil fuels if we want to stabilise climate conditions and avoid a further worsening of these drought events, which will become more frequent and more intense with any additional increase of global warming.”

Climate crisis also made drought more likely in the smaller Western and Central European region. As per the researchers’ estimate, human-induced warming made surface drought about five to six times more likely, and agricultural and ecological drought about three to four times more likely. 

It is important to mention this does not mean that global warming has had less influence on Europe than elsewhere in the Northern Hemisphere – the different sizes of the regions mean the results cannot be directly compared.

The scientists calculated that a drought like this summer’s can be expected around once in 20 years in both regions in today’s climate, which has been warmed by human greenhouse gas emissions. 

This means that, if humans had not warmed the planet, the agricultural drought in the Northern Hemisphere would only have been expected around once in 400 years or less, whereas the European agricultural and ecological drought would have occurred around once in 60 to 80 years.

“Heat and drought in Europe this summer not only caused tens of thousands of direct deaths, but also aggravated the cost of living crisis, compounding the impacts of the Ukraine war,” Maarten van Aalst, professor of climate and disaster resilience at the University of Twente, said. 

“We are witnessing the fingerprint of climate change not just in specific hazards, but also in the cascading of impacts across sectors and regions.”

The study was conducted by 21 researchers as part of the World Weather Attribution group, including scientists from institutions in Switzerland, France, the Netherlands, New Zealand, the UK and the US.