Essay by Eric Worrall
Enhanced mixing of air layers at high altitudes is apparently reducing maximum air temperatures in some parts of the Himalayas.
Scientists uncover surprising phenomenon in the Himalayas slowing the effects of climate change
By CNN 6:41pm Dec 13, 2023
Glaciers in the Himalayas are melting rapidly, but a new report showed an astonishing phenomenon in the world’s tallest mountain range could be helping to slow the effects of the global climate crisis.
When warming temperatures hit certain high-altitude ice masses, it sets off a surprising reaction that blows robust cold winds down the slopes, according to the study published December 4 in the journal Nature Geoscience.
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At the base of Mount Everest, however, measurements of overall temperature averages appeared curiously stable instead of increasing.
A close analysis of the data revealed what was really happening.
“While the minimum temperatures have been steadily on the rise, the surface temperature maxima in summer were consistently dropping,” said Franco Salerno, coauthor of the report and researcher for the National Research Council of Italy, or CNR.
However, even the presence of these cooling winds is not enough to fully counteract increasing temperatures and glacier melt due to climate change.
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“Katabatic winds are a common feature of Himalayan glaciers and their valleys, and have likely always occurred,” Pellicciotti said.
“What we observe however is a significant increase in intensity and duration of katabatic winds, and this is due to the fact that the surrounding air temperatures have increased in a warming world.”
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Read more: https://www.9news.com.au/world/climate-change-news-himalayas-might-be-slowing-the-effects-of-climate-change/23097b04-cc8c-4f9e-be8e-9161417c4301
The abstract of the study;
Local cooling and drying induced by Himalayan glaciers under global warming
Franco Salerno, Nicolas Guyennon, Kun Yang, Thomas E. Shaw, Changgui Lin, Nicola Colombo, Emanuele Romano, Stephan Gruber, Tobias Bolch, Andrea Alessandri, Paolo Cristofanelli, Davide Putero, Guglielmina Diolaiuti, Gianni Tartari, Gianpietro Verza, Sudeep Thakuri, Gianpaolo Balsamo, Evan S. Miles & Francesca Pellicciotti
Nature Geoscience volume 16, pages 1120–1127 (2023)Cite this article
Abstract
Understanding the response of Himalayan glaciers to global warming is vital because of their role as a water source for the Asian subcontinent. However, great uncertainties still exist on the climate drivers of past and present glacier changes across scales. Here, we analyse continuous hourly climate station data from a glacierized elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis. We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming. Reanalysis data suggest a broader occurrence of this effect in the glacierized areas of the Himalaya. We hypothesize that the counterintuitive cooling is caused by enhanced sensible heat exchange and the associated increase in glacier katabatic wind, which draws cool air downward from higher elevations. The stronger katabatic winds have also lowered the elevation of local wind convergence, thereby diminishing precipitation in glacial areas and negatively affecting glacier mass balance. This local cooling may have partially preserved glaciers from melting and could help protect the periglacial environment.
Read more: https://www.nature.com/articles/s41561-023-01331-y
The maximum temperature trend may be cooling at -0.26C per decade at some stations, according to the study.
… Crucially, we find that the overall decreasing Tmax trend at Pyramidoff, particularly during the warm season, is correctly reproduced by ERA5-Land reanalysis (−0.026 ± 0.014 °C yr−1, P < 0.05, Fig. 1e,f), which reproduces the non-stationary patterns at the annual and monthly scale (Fig. 1c). …
Read more: Same link as above
The situation at higher altitudes seems to depend on whether the location is covered with ice, ice covered regions are cooler.
Note minimum temperatures, and some lower slopes appear to be warming. The study also mentioned more precipitation near the foot of glaciers.
The situation is also complex in terms of what is happening at higher altitudes, the study speculates greater layer mixing is causing stronger katabatic winds. The study doesn’t seem to suggest increased precipitation at higher altitudes, instead it reports an overall drying, which could negatively impact glacier mass. The study appears to suggest the drying is caused by increased downhill katabatic winds driving away the moist lowland air. The study mentions the vegetation line on the mountains is stable – not exactly what you would expect in a rapidly warming world – though the study mentions more observations are needed to confirm trends and hypothesis. There were significant gaps in the data which were filled using statistical techniques.
My interpretation, this study likely casts doubt on the wild predictions we’ve heard over the years about the disappearance of this or that snow field or glacier. The situation is obviously a lot more complex than a simple projection based on average global or regional temperature.
