Columbia Climate School: Unexplained Heat-Wave 'Hotspots' Are Popping Up Across the Globe

[OKIsItJustMe]

https://news.climate.columbia.edu/2024/11/26/unexplained-heat-wave-hotspots-are-popping-up-across-the-globe/

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

by Kevin Krajick

November 26, 2024
Earth’s hottest recorded year was 2023, at 2.12 degrees F above the 20th-century average. This surpassed the previous record set in 2016. So far, the 10 hottest yearly average temperatures have occurred in the past decade. And, with the hottest summer and hottest single day, 2024 is on track to set yet another record.

All this may not be breaking news to everyone, but amid this upward march in average temperatures, a striking new phenomenon is emerging: distinct regions are seeing repeated heat waves that are so extreme, they fall far beyond what any model of global warming can predict or explain. A new study provides the first worldwide map of such regions, which show up on every continent except Antarctica like giant, angry skin blotches. In recent years these heat waves have killed tens of thousands of people, withered crops and forests, and sparked devastating wildfires.

“The large and unexpected margins by which recent regional-scale extremes have broken earlier records have raised questions about the degree to which climate models can provide adequate estimates of relations between global mean temperature changes and regional climate risks,” says the study.

“This is about extreme trends that are the outcome of physical interactions we might not completely understand,” said lead author Kai Kornhuber, an adjunct scientist at the Columbia Climate School’s Lamont-Doherty Earth Observatory. “These regions become temporary hothouses.” Kornhuber is also a senior research scholar at the International Institute for Applied Systems Analysis in Austria.

…


Regions where observed heat waves exceed trends from climate models. Boxed areas with the darkest red colors are the most extreme; lesser reds and oranges exceed models, but not by as much. Yellows roughly match models, while greens and blues are below what models would project. (Adapted from Kornhuber et al., PNAS 2024)

…

https://doi.org/10.1073/pnas.2411258121

Global emergence of regional heatwave hotspots outpaces climate model simulations
…
November 26, 2024
…
Significance
Heatwaves can lead to considerable impacts on societal and natural systems. Accurate simulation of their response to warming is important for adaptation to potential climate futures. Here, we quantify changes of extreme temperatures worldwide over recent decades. We find an emergence of hotspots where the hottest temperatures are warming significantly faster than more moderate temperatures. In these regions, trends are largely underestimated in climate model simulations. Globally aggregated, we find that models struggle with both ends of the trend distribution, with positive trends being underestimated most, while moderate trends are well reproduced. Our findings highlight the need to better understand and model extreme heat and to rapidly mitigate greenhouse gas emissions to avoid further harm.

Abstract
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.

…

Uh…