Speaker: Ethan Coffel  
Title: Rapid rise in heat stress exposure during the 21st century
Abstract: Heat stress is a top weather related killer in the U.S. and globally. As a results
of rising temperatures and steady or slightly rising levels of specific humidity, heat stress
-- which is less studied than temperature despite being more directly related to the human
body's ability to cool itself -- is projected to become increasingly severe. Here we show
that heat stress as measured by the wet bulb temperature is projected to rapidly and
dramatically increase by mid-century leading to an at least once-per-year occurrence of
potentially crippling conditions across some of the most densely populated regions of the
planet. We use spatially explicit population projections coupled with the CMIP5 climate
model suite to project that, by the 2060s, hundreds of millions of people could be exposed
each year to heat stress that approaches theoretical thresholds for human tolerance. Some
of the most affected regions currently have scarce cooling infrastructure, relatively low
adaptive capacity, and rapidly rising populations. Our results suggest that as the century
progresses heat stress, coupled with other more widely appreciated climate change impacts,
will pose a severe threat to human health, infrastructure, agriculture, and economic
performance, creating a significant societal stress and necessitating rapid adaptation.