Heatwaves to increase in frequency, duration under global warming – Watts Up With That?

When I saw this press release from Portland State University, I knew I would not have to look far to spot the bias and/or error. First it’s a climate model, second, it’s the WORST climate model, CMIP6 -Anthony

Via Eurekalert:
As the climate becomes warmer on average, it makes intuitive sense that we will see more hot days and we’ve had predictions of this for some time. However, the duration of heatwaves — how many days in a row exceed a temperature that is unusually hot for a given region — can be very important for impacts on humans, livestock and ecosystems. Predicting how these durations will change under a long-term warming trend is more challenging because day-to-day temperatures are correlated — tomorrow’s temperatures have a dependence on today’s temperature.

This study takes this effect into account, along with the warming seen in current and historical observations and projected for the future by climate models for a wide range of land regions. Not only do the heatwave durations increase, but each additional increment of warming causes a larger increase in the typical length of long heat waves. In other words, if the next decade brings as much large-scale warming as a previous decade, the additional increase in heatwave durations would be even larger than we’ve experienced so far.

Abstract

Heatwaves are expected to both increase in frequency and duration under global warming. The probability distributions of heatwave durations are shaped by day-to-day correlations in temperature and so cannot be simply inferred from changes in the probabilities of daily temperature extremes. Here we show from statistical analysis of global historical and projected temperature data that changes in long-duration heatwaves increase nonlinearly with temperature. Specifically, from analysis informed by theory for autocorrelated fluctuations applied to European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) reanalysis and Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model simulations, we find that the nonlinearity results in acceleration of the rate increase with warming; that is, each increment of regional time-averaged warming increases the characteristic duration scale of long heatwaves more than the previous increment. We show that the curve for this acceleration can be approximately collapsed onto a single dependence across regions by normalizing by local temperature variability. Projections of future change can thus be compared to observations of recent change over part of their range, which supports the near-future-projected acceleration. We also find that the longest, most uncommon heatwaves for a given region have the greatest increase in likelihood, yielding a compounding source of nonlinear impacts.

Journal Nature Geoscience

DOI/Link: 10.1038/s41561-025-01737-w 

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