Climate change is behind the Horn of Africa drought, study finds

A devastating drought in the Horn of Africa, which has now stretched across five straight failed rainy seasons, would not have occurred without human-caused climate change, a new study found.

Why it matters: According to a new scientific analysis, climate change sparked by human emissions are exacerbating the region's arid conditions, as well as the suffering of tens of millions of people.

• The drought has created one world's worst humanitarian crises. At least 36.4 million people in the Horn of Africa this year will need emergency assistance to survive, according to the United Nations Office for the Coordination of Humanitarian Affairs (OCHA).

Zoom in: The report was released Thursday by the World Weather Attribution group, an international team of scientists specializing in teasing out climate change's influence on high-impact extreme weather and climate events.

• The study's conclusions are among the strongest this group has made when dissecting extreme events worldwide.
• The 19 researchers from Africa, Europe and the U.S. looked at rainfall trends over a 24-month period, from January 2021 to December 2022.
• They also examined the rainfall received during the "short rains" season, from October through December, as well as the "long rains" from March through May, beginning in 2021.
• They found that below average rainfall during the short rains was most likely tied to the presence of a La Niña event in the tropical Pacific, rather than climate change.
• The long rains, on the other hand, are becoming drier as the global climate warms, with below average rainfall now about twice as likely as before the preindustrial era.

Between the lines: Importantly, the researchers examined changes in moisture loss rates, known as evapotranspiration, from plants and soils as a result of higher temperatures.

• In general, the hotter it gets, the more moisture is lost from the Earth's surface, worsening drought conditions.
• The study found that moisture loss showed the strongest link to human-caused climate change, with a "conservative estimate" that such intense droughts, with extreme heat and moisture loss plus below average rainfall, are at least 100 times more likely to occur now than they were in the preindustrial era.

The intrigue: The region studied includes southern Ethiopia, southern Somalia and eastern Kenya, which is mired in an "exceptional drought," the U.S. Drought Monitor's worst category.

• Without warmer temperatures from climate change, drought conditions either would not have existed at all, or would have ranked in the least severe category, the study found.

What they're saying: Friederike Otto, a climate scientist at the Grantham Institute at Imperial College London, said higher temperatures are key to explaining why this drought would not have occurred without climate change.

• "The same kind of 20-year rainfall event is now an exceptional drought, because the evaporation is so much higher," Otto said during a conference call with reporters Wednesday. She pinned the blame for that on climate change.

The big picture: The unique study goes beyond climate science to emphasize the impact the drought is having across a vulnerable region.

• More than 23 million people across Ethiopia, Kenya and Somalia are "highly food insecure and face severe hunger and water shortages," the U.N.'s refugee agency estimates.
• At the same time, millions across the region have been displaced and some areas are struggling to cope with outbreaks of waterborne diseases like cholera.
• The crisis is especially severe in Somalia. Up to 43,000 people — half of them under the age of 5 — died last year to the drought, according to the World Health Organization.
• Aid groups have repeatedly called on the international community to do more to address the crisis, but the U.N. fund for humanitarian assistance in East Africa remains woefully underfunded.

How they did it: The research is based on peer reviewed methodology, but has not yet undergone its own review. The scientists examined rainfall and temperature data from ground-based weather stations, as well as other observational sources.

• They also looked at climate models to find how well they captured recent trends, and ran them both with and without increased amounts of planet-warming greenhouse gases.
• This helped to determine the roles climate change may be playing.

The bottom line: What is happening now in Africa is likely to play out elsewhere as climate change continues.

• "The impacts of climate change strongly depend on how vulnerable we are," Otto said in a statement, referencing the latest U.N. Intergovernmental Panel on Climate Change report. "We are way more vulnerable than we thought."