National Aeronautics and Space Administration Jet Propulsion Laboratory
National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Science Question: Observed extreme global humid heat has not previously been comprehensively surveyed using weather-station data. Here we conduct such an analysis, including extensive novel efforts to impose additional quality control. The emergence of heat and humidity too severe for human tolerance Colin Raymond (JPL/Caltech), Tom Matthews (Loughborough Univ. ), Radley Horton (Columbia Univ. ) Results: Previous studies, which used reanalysis datasets, underestimated humid-heat extremes considerably. Global maxima are much higher than previously known, concentrated in a few distinct regions, and humid heat overall has more than doubled in frequency since 1979. Figure Caption: Observed global extreme humid heat. Color symbols represent the 99. 9 th percentile of observed daily-maximum TW for 1979 -2017 for Had. ISD stations with at least 50% data availability over this period. Marker size is inversely proportional to station density. Significance: The highest values exceed the level that is physiologically survivable with prolonged exposure. Our results emphasize the danger associated with continued rapid increases in atmospheric heat and humidity, especially for subtropical hotspots where exceptional heat and humidity can collide. Raymond, C. , Matthews, T. K. , and Horton, R. M. (2020). The emergence of heat and humidity too severe for human tolerance. Science Advances, 6, 19. doi: 10. 1126/sciadv. aaw 1838. Partly supported by NASA’s NCA Enabling Tools program (Jack Kaye, Program Manager). Figure Caption: Global trends in extreme humid heat. Plotted are annual global counts of TW exceedances above thresholds labeled on the respective panel, from Had. ISD (black, right axes, with units of station-days), and ERA-Interim grid points (gray, left axes, with units of grid-point-days). We consider only Had. ISD stations with at least 50% data availability over 1979 -2017. Correlations between the series are annotated in the top left of each panel, and dotted lines highlight linear trends.
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