Malaria trends in Ethiopian highlands track the 2000 'slowdown' in global warming

A counterargument to the importance of climate change for malaria transmission has been that regions where an effect of warmer temperatures is expected, have experienced a marked decrease in seasonal epidemic size since the turn of the new century. This decline has been observed in the densely populated highlands of East Africa at the center of the earlier debate on causes of the pronounced increase in epidemic size from the 1970s to the 1990s. The turnaround of the incidence trend around 2000 is documented here with an extensive temporal record for malaria cases for both Plasmodium falciparum and Plasmodium vivax in an Ethiopian highland. With statistical analyses and a process-based transmission model, we show that this decline was driven by the transient slowdown in global warming and associated changes in climate variability, especially ENSO. Decadal changes in temperature and concurrent climate variability facilitated rather than opposed the effect of interventions. The effect of climate change on highland malaria transmission remains unclear because of increasing and decreasing trends. Here, Rodo et al. analyze malaria case data and climate data for the Ethiopian highlands from 1968 to 2008 and find that changes in temperature and associated climate variability facilitated the effect of interventions at the beginning of the 21st century.

Automated summary

A counterargument to climate change's impact on malaria transmission is that regions experiencing warmer temperatures have actually seen a decrease in seasonal epidemic size since the early 2000s. The decline in malaria cases in the Ethiopian highlands was driven by a transient slowdown in global warming and changes in climate variability, particularly ENSO. Decadal changes in temperature and climate variability were found to facilitate the effectiveness of interventions in combating malaria in the early 21st century.