‘So Many Dimensions’: A Drought Study Underlines the Complexity of Climate

Back-to-back years of little precipitation in the Indian Ocean nation of Madagascar have ruined harvests and caused hundreds of thousands of people to face uncertainty about their next meals. Aid groups say the situation there is nearing a humanitarian catastrophe.

But human-induced climate change does not appear to be the driving cause, a team of climate scientists said on Wednesday.

Rainfall in the hard-hit south of Madagascar naturally fluctuates quite a lot, the researchers said, and they did not find that a warming climate was making prolonged droughts significantly more likely.

Even so, they emphasized the island should still aim to bolster its ability to cope with dry spells. Scientists convened by the United Nations have determined that droughts in Madagascar as a whole will likely increase if global average temperatures rise by more than 2 degrees Celsius — a higher level of warming than the 1.2 degrees that was considered in the new analysis.

Average global temperatures have already increased by 1.1 degrees Celsius compared with preindustrial levels. Scientists have said that nations need to try to prevent temperatures from rising more than 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, which is the threshold beyond which they say the likelihood of catastrophic fires, floods, drought, heat waves and other disasters significantly increases. Current policies put the planet on pace for roughly 3 degrees Celsius of warming by 2100.

“What it shows is that the current climate variability is already resulting in severe humanitarian suffering,” said Maarten van Aalst, director of the Red Cross Red Crescent Climate Center and one of the 20 scientists involved in the Madagascar study. “In these sorts of places, anything that climate change would make worse would become a really big additional problem really quickly.”

Madagascar, a large island off Africa’s eastern coast, is known for its sandy beaches, emerald waters and ring-tailed lemurs. But low rainfall since 2019 in the nation’s southwestern end — which is known as Le Grand Sud, or the Deep South — has left that part of the island in a dire state.

More than 1.3 million people, or nearly half the Grand Sud’s population, are experiencing high levels of food insecurity, according to the United Nations. Half a million children under the age of 5 are at risk of severe malnutrition.

The climate researchers estimated that such a long dryspell had a one-in-135 chance of occurring in any given year in that part of Madagascar.

Environmental degradation has exacerbated the drought’s effects. Sandstorms fueled by deforestation have ruined cropland and pastures. An outbreak of locusts threatens further destruction.

Residents of the Grand Sud have been forced to eat grass, leaves and even clay to survive, the United Nations World Food Program has found. Children have quit school to help their families forage for food. Amnesty International has collected testimonies suggesting that some people have died of hunger.

The analysis of the drought was conducted by an international scientific collaboration called the World Weather Attribution initiative, which specializes in pinpointing the links between climate change and individual weather events. The group performs such analyses with a speed that is unusual in the scientific publishing world: It aims to present sound science to the public while events are still fresh in people’s minds.

The team’s Madagascar study has not been peer reviewed, though it relies on peer-reviewed methods. Essentially, the approach is to use computer simulations to compare the existing world, in which humans have pumped greenhouse gases into the atmosphere, to a hypothetical one without that activity.

It may seem counterintuitive that global warming does not contribute to a clear increase in the likelihood of drought. Scientists have found, however, that the relationship is not so simple. Climate change generally causes more intense rain events, but it also shifts rainfall patterns.

“Drought has so many dimensions,” Dr. van Aalst said. “It’s not as straightforward as just, how much average annual rainfall do you get? The question is also, do you get it nicely distributed, or do you just get it in massive amounts at once? Do you get it in the right seasons?”

“We have to be a bit careful,” he added, “drawing too straight a line from purely our precipitation observations or projections to what people in the end suffer from.”

World Weather Attribution has linked other extreme weather events to human-caused climate change in recent years. The group found that this summer’s extraordinary heat wave in the Pacific Northwest almost certainly would not have occurred without it.

For climate scientists, “droughts are a combination of factors that’s much more difficult to deal with” than, say, heat waves, said Piotr Wolski of the Climate System Analysis Group at the University of Cape Town in South Africa.

“We have this predominant narrative these days that droughts are driven largely by anthropogenic climate change,” said Dr. Wolski, who also worked on the Madagascar study. “It’s not a bad narrative, because they are — it’s just not everywhere and not in every single case.”

In Madagascar, livelihoods are easily destabilized by wild swings in precipitation, said Daniel Osgood, a research scientist at the International Research Institute for Climate and Society at Columbia University who was not involved in the study.

Dr. Osgood is working on a project to provide affordable drought insurance to growers in Madagascar. The goal is to help them become more resilient to the economic shocks that weather can bring about. “It’s not how much you eat on average,” he said. “It’s how much you eat every night that really makes a difference.”