According to a scientific study released on Thursday, the record-breaking heatwave that hit Madagascar last month would not have occurred without the added boost from human-caused climate change. The scientists behind the study, from the World Weather Attribution (WWA) group, use a well-established technique to figure out how likely such a heatwave was in a world with nearly 1.2 degrees Celsius of warming since preindustrial times — the amount resulting from burning fossil fuels and large-scale deforestation. They then compare the odds in that world to the actual temperature record set in October.
Using that method, the WWA team found the heatwave was up to 100 times more likely than it would have been without climate change and almost impossible without it. That makes the heatwave a “climatological outlier” and one of the most severe heatwaves in recent memory, they said.
The study focused on southern Madagascar, which is facing a severe food security crisis made worse by below-average rainfall over the last two years. With 90% of the population living below the poverty line, this drought in a region with high vulnerability to hunger has led to tens of thousands facing severe famine-like conditions. The low rains also exacerbated a severe water crisis and boosted COVID-19 restrictions, adding to the overall threat of hunger.
However, scientists found that climate change made the drought more likely but was not its primary driver. “It’s a threat multiplier, and it makes it harder to recover from extreme events, but for this particular event, it was more natural rain variability and the very high vulnerability,” the lead author of the study, Dr. Beth Otto, told the AFP news agency in an email.
As an equatorial island, Madagascar experiences a different climate from Europe and North America, with a wet season from November to April and a dry period from May to October. The rainfall on the west coast and the island’s plateau is moderate, but the arid southwest is protected from rain and experiences slight seasonal variation.
The WWA team used models to determine how the weather was influenced by various factors, including the amount of greenhouse gases in the atmosphere, the ocean’s surface temperatures, and the strength and direction of winds. They also analyzed whether significant events, like volcanic eruptions or solar activity, affected the weather. They then compared that information to the weather records from the past to see how much each factor enhanced or weakened the event. This is the same approach scientists have used to analyze hurricanes, floods, and other weather disasters. The researchers’ findings align with general predictions about how global warming will influence climate extremes. They have called on wealthy countries to increase funding to help poor nations deal with climate impacts, an issue to be discussed at the UN’s COP28 climate summit this week.