Development of Future Heatwaves for Different Hazard Thresholds.

Area of Science:

• Climate Science
• Extreme Weather Events

Background:

• Recent heatwaves in 2018-2019 broke temperature records globally, causing widespread adverse effects.
• Existing research on heatwaves often analyzes spatial or temporal aspects independently, neglecting their joint impact.
• The influence of varying heatwave thresholds on their characteristics in a warming climate is under-researched.

Purpose of the Study:

• To analyze spatiotemporal heatwaves in global climate model simulations.
• To investigate the sensitivity of heatwave characteristics to different hazard threshold definitions under global warming.

Main Methods:

• Analysis of three-dimensional (space-time) clusters of hot days in climate model simulations.
• Utilized three distinct hazard thresholds: fixed, seasonally moving, and fully moving relative to future climatology.

Main Results:

• A substantial increase in spatiotemporally contiguous heatwaves was observed using fixed thresholds with global warming.
• Heatwave changes were less pronounced when using seasonally moving or fully moving thresholds.
• No significant changes in magnitude, spatial extent, or duration were detected with fully moving thresholds, indicating dominant thermodynamic effects.

Conclusions:

• Simulated future heatwave projections are highly sensitive to the chosen hazard thresholds.
• Seasonal mean warming largely explains the warming of extremes, as shown by the similarity between seasonally and fully moving thresholds.
• The findings underscore the importance of considering threshold sensitivity in projecting future heat-related impacts.