"Unexplained Heat-Wave ‘Hotspots’ Are Popping Up Across the Globe"

[raz.org.rain]

An interesting article published by the Columbia Climate School titled Unexplained Heat-Wave ‘Hotspots’ Are Popping Up Across the Globe discusses a new study by Kornhuber, Bartusek et al. (2024). This study discusses the emergence of regional heat anomalies that have outpaced what initial model simulations had suggested as the expected trend by a considerable margin. 

Thomas Reis provided an excellent summary and commentary regarding this study over on Twitter;

"Models seriously underestimate the emergence of extreme heat all across our planet in hot spot regions.

It's becoming ever more obvious, models are unable to simulate all developments whose drivers operate at small scales. And most of the processes that steer our circulation in the atmosphere and oceans are government by small scale physics.

Be it jets, convection, cloud formation, soil moisture, vertical mixing, stratification, latent heat release, land-atmosphere-ocean-sea-ice-interactions, sea ice melting, ocean fronts, marine heatwaves etc.

Name it processes operating at small scales on a hourly/daily basis rule the climate system of Earth, as they operate all the subsystems of Earth. Thereby models not having the computational power to simulate all these small scale processes that are behind all these regional to local drivers of the new emerging class of compound events in which many drivers interact to create the most extreme events far beyond what we thought already possible.

Its simple: climate/Earth system models have to simulate all these processes that operate the subsystems of Earth to be able to simulate the emergent reaction of the whole that is now mutually amplifying non-linear...

Here what they write:

Multiple recent record-shattering weather events raise questions about the adequacy of climate models to effectively predict and prepare for unprecedented climate impacts on human life, infrastructure, and ecosystems. Here, we show that extreme heat in several regions globally is increasing significantly and faster in magnitude than what state-of-the-art climate models have predicted under present warming even after accounting for their regional summer background warming. Across all global land area, models underestimate positive trends exceeding 0.5 °C per decade in widening of the upper tail of extreme surface temperature distributions by a factor of four compared to reanalysis data and exhibit a lower fraction of significantly increasing trends overall. To a lesser degree, models also underestimate observed strong trends of contraction of the upper tails in some areas, while moderate trends are well reproduced in a global perspective. Our results highlight the need to better understand and model the drivers of extreme heat and to rapidly mitigate greenhouse gas emissions to avoid further harm from unexpected weather events."

 

It's a somewhat well known discrepancy that climate models are failing to account for crucial factors and thus underestimate specific impacts by a considerable margin. The Kornhuber, Bartusek et al. (2024) study is the latest to demonstrate how climate model simulations are not efficiently accounting for atmospheric dynamic anomalies, and thus underestimate the warming feedback potential in regions such as northwestern Europe by a substantial margin. This factor was also discussed by Vautard, Cattiaux et al. specifically in relation to Western European warming trajectories in their 2023 study "Heat extremes in Western Europe increasing faster than simulated due to atmospheric circulation trends". It stands to reason that the underestimation of atmospheric anomalies results in a considerable underestimation of present and future heat anomaly potential in the northwestern Europe region.