Global Climate Risks for Outdoor Sports Under CMIP6 Scenarios: A Multi-Indicator Assessment Based on WBGT, Heat Index, Heavy Rainfall, and Heatwaves

Dimitri Defrance, TIffanie Lescure

Outdoor sports are increasingly exposed to climatic conditions that challenge athlete safety, performance and event organisation. Despite extensive physiological and epidemiological evidence on heat stress, no global assessment has yet quantified how multiple climate hazards will jointly constrain outdoor sport under future climate change.

Here we provide the first global, CMIP6-based, multi-indicator assessment of climate-related risks for outdoor sport using bias-corrected daily projections from the NASA NEX-GDDP-CMIP6 dataset at 0.25° resolution. We compute four impact-oriented indicators relevant for sport practice: (i) Wet-Bulb Globe Temperature (WBGT) for morning, afternoon and evening conditions, (ii) dangerous Heat Index days (HI $>40\,^{\circ}$C), (iii) heavy rainfall days (precipitation $>20$~mm~day$^{-1}$), and (iv) heatwave days defined as sequences of at least three consecutive days with $T_{\max}>35\,^{\circ}$C. Indicators are analysed for two contrasted seasons (JJA and DJF) and three 30-year periods (1991--2020, 2031--2060, 2071--2100) under SSP2--4.5 and SSP5--8.5, and combined into a composite Sport Climate Risk Index (SCRI, 0--1).

Results reveal a rapid intensification and spatial expansion of climate constraints on outdoor sport. Under SSP5--8.5, large tropical and subtropical regions exceed 60--80 WBGT extreme-risk days per season by late century, with morning and evening conditions increasingly affected, reducing the effectiveness of time-of-day scheduling as an adaptation strategy. Dangerous Heat Index days frequently exceed two months per season in humid regions, while heatwaves introduce multi-week periods of cumulative thermal stress. Heavy rainfall remains a persistent constraint in monsoonal and equatorial regions, contributing to surface degradation and event cancellations. The SCRI highlights continental-scale hotspots where multiple hazards co-occur, with values exceeding 0.8 across much of the tropics by 2071--2100, indicating that outdoor sport becomes barely viable without major adaptation.

The divergence between SSP2--4.5 and SSP5--8.5 demonstrates that mitigation choices critically determine the future climatic feasibility of outdoor sport. By providing a coherent global baseline across multiple hazards, seasons and time-of-day exposures, this study establishes a quantitative foundation for climate-aware sport scheduling, infrastructure planning and adaptation strategies in a warming world.