The entire scientific community agrees that climate change is the biggest threat to life as we know it. However, how exactly climate change will impact human health, and in particular the transmission of vector-borne diseases such as malaria, is still a matter of debate.

“We believe that one of the largest impacts of global warming on malaria incidence will occur in the highlands, where for the moment lower temperatures limit vector abundance,” says Xavier Rodó, who heads the Climate and Health Programme.

The case of East Africa

Rodó and his colleagues focused on the region of Oromia in Ethiopia, a densely populated highland between 1,600 and 2,500 metres above sea level. This region, like the rest of East Africa, saw a clear decrease in malaria incidence at the turn of the century, right after a temporary slowdown in global warming was observed, between 1998 and 2005. Using mathematical modelling, the research team analysed the association between malaria cases, regional climate (local temperatures and rainfall) and global climate. The fact that Ethiopia did not reinforce public health interventions to control the disease until 2004 made it possible to clearly separate the effect of climate from the effect of control measures.

The results show that the slowdown in global warming led to a decrease in regional temperatures, which in turn led to a reduction in malaria incidence, before control measures were reinforced. “Our findings demonstrate that malaria epidemiology in these areas is strongly under climate control at all scales (months, years and even decades) and settle once and for all the debate on whether climate change affects malaria transmission in Africa,” says Rodó.