Climate change fingerprints found on this summer's scorching droughts

INA-  SOURCES 

Human-caused climate change made the drought conditions that gripped large portions of the Northern Hemisphere this past summer far more likely to occur, a new study found. 
Why it matters: The study, published Wednesday, found human-caused global warming dramatically upped the odds of drought throughout the hemisphere outside of the tropics — making them at least 20 times more likely compared to the preindustrial era. 

• The Northern Hemisphere summer of 2022 brought extreme heat and drought to Europe, China and North America. 
• Drought conditions tied to the heat caused water shortages in the Western U.S., led to rivers running critically low in countries like Germany, and caused food prices to increase. 
• The drought conditions harmed agricultural output at the same time as unrelated factors, such as the war in Ukraine, were exerting upward pressure on food prices. 

• The new study, published using peer-reviewed methods by the 21 members of the World Weather Attribution group, a global collective of researchers that examine the ties between extreme weather events and human-caused climate change, focused on changes in soil moisture as a key drought metric. 
• Warmer temperatures are the primary cause of the increase in drought likelihood, the study finds, since hotter weather increases evaporation from soils and plants. 
• The new research estimates that human-caused climate change made soil moisture drought conditions much more likely, by about a factor of 20, though the study's authors cautioned that there is a significant amount of uncertainty associated with that specific number.
• "Our analysis shows that last summer's severe drought conditions across large parts of the Northern Hemisphere were fueled by human-induced climate change," said Dominik Schumacher, of ETH Zurich, in a statement. "With further global warming we can expect stronger and more frequent summer droughts in the future."

• This is the depth of soil that most plants draw water from, so dry soils there can have a particularly large effect on agriculture. 

• The international team of researchers also focused on Western and Central Europe, which saw an especially severe drought from the Atlantic to the eastern Black Sea. 

• The study found that for this region, climate change made surface drought up to 6 times more likely to occur, while root zone drought, which is also known as agricultural and ecological drought, was 3 to 4 times more likely. 

• "The exact quantification of that role is more uncertain for soil moisture than, for example, when we look at heavy precipitation," she said.