Anthropogenic forcing has increased the risk of longer-traveling and slower-moving large contiguous heatwaves

Abstract

Heatwaves are consecutive hot days with devastating impacts on human health and the environment. These events may evolve across both space and time, characterizing a spatiotemporally contiguous propagation pattern that has not been fully understood. Here, we track the spatiotemporally contiguous heatwaves in both reanalysis datasets and model simulations and examine their moving patterns (i.e., moving distance, speed, and direction) in different continents and periods. Substantial changes in contiguous heatwaves have been identified from 1979 to 2020, with longer persistence, longer traveling distance, and slower propagation. These changes have been amplified since 1997, probably due to the weakening of eddy kinetic energy, zonal wind, and anthropogenic forcing. The results suggest that longer-lived, longer-traveling, and slower-moving contiguous heatwaves will cause more devastating impacts on human health and the environment in the future if greenhouse gas emissions keep rising and no effective measures are taken immediately. Our findings provide important implications for the adaption and mitigation of globally connected extreme heatwaves.

Longer‐ and Slower‐Moving Contiguous Heatwaves Linked to El Niño

“…The comparison between the model outputs and observations may provide more insights into the processes and mechanisms responsible for the changes in the evolution of contiguous heatwaves due to ENSO effects. Previous studies have indicated that El Niño events will be more frequent and the contiguous heatwaves will be slowermoving as the Earth warms (Cai et al, 2014;Luo et al, 2024). Thus, further study is required to examine the modulation of ENSO activity on the moving pattern of contiguous heatwaves in the future, and quantify to what degree the future changes in heatwaves are attributable to anthropogenic warming and ENSO activity.…”

“…In the current study, we provide the global investigation of the relationship between ENSO and the multidimensional properties (Table S1 in Supporting Information S1) of contiguous heatwaves across the global land areas, with a particular focus on their spatiotemporal evolution patterns, including moving direction, distance, and speed. Contiguous heatwaves are identified by using the spatiotemporally contiguous event tracking (SCET) method (Luo, Lau, et al, 2022;Luo et al, 2024), which was initially introduced to discern connected components in multilabel 3D (i.e., latitude × longitude × time) images (Figure S1 in Supporting Information S1; see Methods) (Silversmith, 2021).…”

“…Few studies have explored the behaviors of the spatiotemporally contiguous heatwaves (Keellings & Moradkhani, 2020;Luo, Lau, et al, 2022;Luo et al, 2024;Lyon et al, 2019). For instance, Keellings and Moradkhani (2020) have noted an expansion in the areal extent of contiguous heatwaves in the United States.…”

A study on the monitoring of heatwaves and bivariate frequency analysis based on mortality risk assessment in Wuhan, China

“…A case study in Shanghai found that a 1°C increase in global mean temperature could lead to a 36.1% surge in annual peak electricity use ( 9 ). Luo et al ( 10 ) found that slowdown in the movement of heat waves in recent decades could increase the risk of reduced productivity of local ecosystems and increase consumption and capacity needs in the energy sector. Similarly, human health is affected by severe heatwaves.…”

“…In addition, heat wave events have spatial continuity, with heat wave propagation distances, movement speeds and directions changing over time ( 18 ). Recognizing the movement patterns and propagation cycles of heat waves can provide potential precursor signals, and understanding their co-evolution in both temporal and spatial dimensions is important for understanding heat wave prediction, mitigation and adaptation ( 10 ).…”