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Conclusions
Projections of increasing global surface temperature lead to significant transformations in the behavior of high-temperature extremes. Trends in global and local temperatures will transform present-day “once-in-a-lifetime” high-temperature events into frequent (e.g., annual) occurrences in the next several decades. We show that projected temperature trends will exponentially increase the odds of exceeding the 50-year extreme high-temperature events across North America (U.S., Canada, and Mexico) with a doubling time scale of approximately 13–17 years. This doubling time scale is equivalent to a doubling temperature scale of 0.5–1 C rise in the local surface temperatures. With the increased frequency of extreme high-temperature events, we expect a corresponding acceleration of many temperature-related public health concerns (see, e.g., ref.68). Although it is likely that society has yet to fully comprehend the consequences of global temperature rise, we offer that the information provided here can aid in the development of prevention and mitigation plans at regional and global scales.