Evidence of Rapidly Increasing Dangerous Humid-Heat Risk in Africa's Great Green Wall

Abstract

<p>Since the 1980s, air temperatures have precipitously risen across the African Sahel due to climate change. Currently, the Sahel has rapidly greened. While the drivers of such land-cover and land-use change (LCLUC) across this dryland region are debated, development organizations, governments, and multinational organizations have heralded the greening of the Sahel as a solution to land-degradation and as an impetus to improve human health and well being for low-income peoples across the region. Indeed, the Great Green Wall has garnered significant global attention and investment. Yet, the Great Green Wall may increase available moisture across this normally dryland region, which combined with increased air temperatures, can increase the likelihood of dangerous humid-heat conditions that harm human health and reduce economic activity. Despite the implications of the amplification of hot-humid heat extremes due to interactions between LCLUC and climate change along the Great Green Wall, no longitudinal and fine-grained synthesis of these processes exists for the Sahel.</p> <p>Here we merge the highest resolution and most accurate global temperature record – CHIRTS-daily – and down-scaled reanalysis relative humidity estimates with the Long-term Global Land Change dataset to identify where LCLUC converges with increases in dangerous humid-heat events across the Sahel from 1983 - 2016. We find that Sahelian regions that are greening the fastest are significantly more likely to have an increase in dangerous humid-heat compared to non-greening regions. Our initial results suggest that the Great Green Wall may be creating hot-humid heat conditions that may curtail economic growth and that may approach the limits of human survivability as we continue to warm the climate and green the Sahel.</p>