Climate Change Made an Early Heat Wave in West Africa 10 Times as Likely

A remarkably early, record-breaking heat wave hit the southern part of West Africa in mid-February. Climate change made this extreme heat 10 times as likely, according to a new analysis by an international team of scientists. It also pushed the heat index about four degrees Celsius higher than it would have been without the extra greenhouse gases in the atmosphere from burning fossil fuels.

Officials saw the unusual temperatures coming, and national weather agencies in Ghana and Nigeria issued warnings to the public. The Africa Cup of Nations soccer tournament took place in Ivory Coast during the heat wave, and players had to take extra breaks during games to hydrate.

What was particularly arresting about this heat wave was the onset of high temperatures so early in the year, when people have had less time to adjust to rising temperatures. “Many, many people wouldn’t have been acclimatized to the heat,” said Wasiu Adeniyi Ibrahim, head of the Nigerian Meteorological Agency’s central forecast office and an author of the study.

During the heat wave, humidity raised the danger. During the worst of the event, temperatures rose above 40 degrees Celsius, or 104 degrees Fahrenheit. But high humidity meant the air felt even hotter. The heat index, which measures the combined effect of heat and humidity on the human body, rose to around 50 degrees Celsius, or 122 degrees Fahrenheit.

Researchers have limited data about how this heat affected people more broadly across West Africa, and whether it led to many hospitalizations and deaths. But there’s reason to believe there may have been widespread harm, according to Maja Vahlberg, a risk consultant at the Red Cross Red Crescent Climate Centre and one of the authors of the analysis.

Many residents of the region don’t have adequate access to water, energy and sanitation. That means that during heat waves, “people are left with very limited options for individual coping strategies, such as using air-conditioning and drinking or taking more showers,” Ms. Vahlberg said. About half of the region’s urban population lives in informal housing, including homes built with sheet metal, which traps heat.

Older people, those with existing illnesses and outdoor workers are especially vulnerable to extreme heat.

The analysis, by a group known as World Weather Attribution, took longer than similar studies the group’s scientists have done on other extreme weather events. West Africa has less data available from weather stations than other regions of the world, which makes studies linking weather there to climate change more difficult to conduct. But last month’s extreme heat was an early sign, before spring had even started, of things to come both in this region and the rest of the Northern Hemisphere this summer.