Tom Matthews and Tom Wood from the ACE team contributed to the annual State of the Climate report for the Bulletin of the American Meteorological Society (BAMS), writing the section on equivalent temperature in collaboration with Paul Stoy and Michael Byrne.
Extract: “In summary, 2024 was a record-breaking year for equivalent temperature(Teq), with all datasets unanimous in their agreement that it was easily the highest over land and ocean since at least 1979.”
Read our blog post about our contribution on the King’s College London substack:
‘Why 2024’s Record Heat Demands a New Way of Measuring Climate Change’
Extreme heat threatens human life, evidenced by >260,000 heat-related fatalities collectively in the deadliest events since 2000. In this Review, we link physical climate science with heat mortality risk, including crossings of uncompensable thresholds (beyond which human core body temperature rises uncontrollably) and unsurvivable thresholds (lethal core temperature increase within 6 h). Uncompensable thresholds (wet-bulb temperatures ~19–32 °C) depend strongly on age and the combination of air temperature and relative humidity. These thresholds have been breached rarely for younger adults (~2.2% of land area over 1994–2023) but more widely for older adults (~21%). Unsurvivable thresholds (wet-bulb temperatures ~20–34 °C) were only exceeded for older adults (~1.8% of land area). Anthropogenic warming will lead to more frequent threshold crossings, including tripling of the uncompensable land area for young adults if warming reaches 2 °C above preindustrial levels. Interdisciplinary work must improve the understanding of the deadly potential of unprecedented heat and how it can be reduced. Ensuring reliable access for all to cool refugia is an urgent priority as the atmosphere threatens to increasingly overwhelm human physiology under climate warming.
The hottest boreal summer on record has driven widespread humid heat mortality across every continent of the Northern Hemisphere. With critical physiological limits to human heat tolerance drawing ever closer, this Comment highlights the urgent need to limit further climate warming and emphasizes the adaptation challenge ahead.