Study reveals footprint of global warming on 2022 Northern Hemisphere mega-drought

No one expected the wildfire that started burning in early August on the steep, forested hill above Stoliv, Montenegro. Residents of the village said there were no memories among the living population, nor old tales, of a fire on the northern slope just above the Bay of Kotor which is home to ancient chestnut and olive groves.

The Stoliv fire only burned a few acres but threatened homes, as well as a chestnut restoration project and the ruins of a centuries-old monastery, built in what was believed to be the place the safest in the region.

But as the relentless, heat-fueled drought persisted across the northern hemisphere from June to August, it seemed to wipe out the very life of the land, threatening ecosystems as well as water, power and food supplies. . In Europe, the long heat wave is estimated to have killed around 24,000 people.

Droughts this widespread and persistent are 20 times more likely in the current climate, scientists reported today in a new Global Weather Allocation study based on Northern Hemisphere soil moisture measurements and models. Co-author Friederike Ottowith the Grantham InstituteImperial College London, said last summer shows how climate extremes aren’t just short, sharp peaks. They can affect large areas for a long time, damaging infrastructure and overburdening social systems, she said.

A forest fire burns on August 4, 2022 near the town of Stoliv, Montenegro, on a wet, north-facing mountain slope with no history of a forest fire. Credit: Bob Berwyn

Hemispheric mega-droughts will intensify even more as long as fossil fuel pollution continues to build up in the atmosphere, the co-author said. Maarten of Aalstdirector of the Red Cross Red Crescent Climate Center and Professor of Climate and Disaster Resilience at the University of Twente.

“These are major impacts happening faster and on a larger scale than we anticipated,” he said. But reducing greenhouse gases will, at best, prevent the extremes from getting any worse. “We have to deal with what already exists,” he said. “Adaptation is urgent. It is no longer a choice to try to avoid these problems in the future by reducing emissions.

With food security under threat in many regions, it comes down to a question of how global resources are allocated, he added.

“There is, at this point, no absolute shortage of food in the world,” he said. “So to some extent it’s a question of whether we’re getting the food to the right people at the right time and, in that sense, also whether we’re allocating the financial resources to solve the problem, everywhere.”

The authors noted that oscillations between different types of extremes pose another set of problems. In 2016, water managers in France expected a hot and dry summer and kept the reservoirs full. Instead, heavy rains fell, leading to disastrous flooding.

Otto said the new study focused specifically on agricultural and ecological drought, defined by lack of soil moisture. Other types of studies that look at different metrics like rainfall or river flows might yield different results, she said.

Co-author Sonia Seneviratnewith ETH Zürich, said this important definition of drought was also used in a recent climate assessment by the Intergovernmental Panel on Climate Change that identified the impacts of global warming.

Without human influence on the climate system, researchers would have expected such an event in west-central Europe only once every 60 to 80 years, she said. But “under the current level of global warming, so about 1.2 degrees Celsius, this is an event people would now expect about once every 20 years.”

Co-author Dominik Schumacher, a researcher at ETH Zurich’s Institute for Atmospheric and Climate Sciences, said the study shows that more danger looms with more warming. Uncertainties in the attribution study, primarily coupled with a lack of direct observations of soil moisture, mean that climate models have only limited data to work with, reducing the accuracy of projections, a he declared. But the findings of the increased frequency of droughts are strong and essential for understanding the impacts on agriculture and ecosystems like forests and wetlands, he added.

Impacts hit harder and sooner than expected

The footprint of climate change is clear in west-central Europe, van Aalst said.

“It hits us really hard, in some of the wealthier parts of the world that were actually considered less vulnerable,” he said. “I don’t think people realized the impacts would hit us so hard, so quickly.”

Heat is the main driver in terms of direct climate impacts on ecosystems and humans, with reports of at least 24,000 additional deaths in Europe, he said. The drought is part of a cascade of thermal impacts piling up on top of each other, he added.

“If you look at agricultural and ecological drought, we see the impacts worsening and rippling through regions and sectors. This is another message that came so strongly from the IPCC earlier this year,” he said, noting that droughts also affect power generation and river transport. “One case where we saw these combined and cascading risks very clearly was in electricity supply, where we saw low hydro generation, but also nuclear power struggling to dump water cooling in rivers that were already too warm,” he said.

This pushed up electricity prices which were already inflated due to the gas supply cut caused by the war in Ukraine. At the same time, heat waves were causing Europeans to use more electricity to run their air conditioners.

“You can see we’re seeing ripples of this direct fingerprint of climate change with very immediate impacts,” van Aalst said. “That should be a wake-up call, that we should avoid letting this problem get more out of control, to reduce emissions.”

“But we also need to invest more in resilience,” he said, noting that abrupt swings in climate change can complicate those efforts. “Some regions face trade-offs, where in some cases how we prepare for extreme rainfall may be at odds with how we prepare for extreme droughts like this.”

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Links between global warming and dry and wet extremes have been well known for decades, a climatologist says Jennifer Francois with the Woodwell Climate Research Center.

“A warmer atmosphere sucks more moisture from land and ocean, creating a vicious cycle that leads to drier soils, which in turn warm faster and intensify heat waves,” he said. she declared. “More intense heat waves dry out the ground even further, extending hot air domes in an area. And when a storm forms, that extra moisture evaporated into the air fuels heavier downpours and provides more energy for stronger storms.

Francis, who was not involved in the attribution study, studied how global warming shifts critical winds like the jet stream that determines weather patterns in the northern hemisphere.

“When the jet is very wavy, as it was last June, the stage is set for both extremes,” she said. “Big jet stream waves also tend to get stuck, which means the weather they create lasts longer. Recent studies suggest that these wavy patterns occur more frequently as the Earth continues to warm, so we should expect to see longer, more intense, and more destructive droughts and floods.

Averting runaway climate change requires drastic and rapid reductions in greenhouse gas emissions, she said.

“If we can meet our 2030 and 2050 climate goals, and that’s a very big if, we’ll slow the rate of worsening extremes by mid-century,” she said. “The sooner we can stop the rise of greenhouse gases in the atmosphere, the sooner we will see Earth’s temperatures approaching a stable level. But the longer we wait, the higher this stable temperature will be, as well as the severity of extreme weather events. »

Teresa H. Sadler