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The Effect of Forced and Unforced Variability on Heat Waves, Temperature Extremes, and Associated Population Risk in a CO2-Warmed World
  • Jangho Lee,
  • Jeffrey C. Mast,
  • Andrew E. Dessler
Jangho Lee
Texas A&M University
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Jeffrey C. Mast
Texas A&M
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Andrew E. Dessler
Texas A&M University

Corresponding Author:[email protected]

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This study investigates the impact of global warming heat and humidity extremes by analyzing 6-hourly output from 28 members of the Max Planck Institute Grand Ensemble driven by forcing from a 1%/year CO2 increase. We find that unforced variability drives large changes in regional exposure to extremes in different ensemble members, and these variations are mostly associated with ENSO variability. However, while the unforced variability of the climate can alter the occurrence of extremes regionally, variability within the ensemble decreases significantly as one looks at larger regions or at a global population perspective. This means that, for metrics of extreme heat and humidity analyzed here, forced variability of the climate is more important than the unforced variability at global scales. Lastly, we found that most heat wave metrics will increase significantly between 1.5°C and 2.0°C, and that low GDP regions shows significant higher risks of facing extreme heat events compared to high GDP regions. Considering the limited economic adaptability of population on heat extremes, this reinforces the idea that the most severe impacts of climate change may fall mostly on those least capable to adapt.