Something is slowing down climate change in the Himalayas

Photo of a valley in the Himalayas with a river flowing through it.
Image by Sukant Sharma on Unsplash
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Scientists have been surprised to find a phenomenon that has been slowing down climate change in the Himalayas.

Like elsewhere, Himalayan glaciers are also impacted by the changing climate. Rising temperatures are exacerbating ice-losses due to an increase in the lengthening and intensification of the melt season. This results in the thinning and melting of glaciers, which makes the landscape more prone to absorbing heat energy due to the albedo effect (the ability of surfaces to reflect sunlight/heat from the sun), thus further increasing air temperatures. A previous study by ICIMOD showed that glaciers in the Himalayas melted 65% faster in the 2010s compared with the previous decade.

This new study, however, gives a modicum of good news. Something might be helping to slow the effects of the global climate crisis in the Himalayan region. The team of researchers analysed “continuous hourly climate station data from a glacierised elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis”.

The scientists say: “We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming.”

“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.”, they continue.

As climate becomes warmer, there is a greater temperature gap between the air surrounding the Himalayan glaciers from above, and the cooler air directly touching the surface of the ice mass.

“This leads to an increase in turbulent heat exchange at the glacier’s surface and stronger cooling of the surface air mass,” Francesca Pellicciotti, professor of glaciology at the Institute of Science and Technology Austria and lead author of the study said in a news release.

Basically, as the cool dry surface air gets colder, it becomes denser and sinks downhill like a waterfall of air. This flow, known as katabatic winds, carries the chill into the valleys and surrounding ecosystems, causing cooling in the lower areas and, overall, influencing the climate of the region and its ecosystems.

“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.”

Diagram for non-stationary conditions (subscript 1). Currently, global warming increases the flux of sensible heat toward the glacier surface and thus enhances the cooling of near-glacier-surface air. Consequently, katabatic winds become more intense and capable of drawing further cold air masses from the higher elevations. As a result, the glacier cooling effect reaches downstream the periglacial environment (from II0 to II1), downshifting the convergence zone (from III0 to III1). Ts, temperature of glacier surface; Ta, temperature ambient; Tfa, temperature of free atmosphere; Tg, 2 m on-glacier temperature.

Schematic diagrams explaining the air cooling observed in the surroundings of Himalayan glaciers.

When overall temperatures were measured at the base of Mount Everest, they appeared to be stable instead of increasing.

“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.

Furthermore, the data also showed that the concentration of ground-level ozone was higher with lower temperatures. This means that the katabatic winds transport cold air from the higher elevation and atmphospheric layers down to the valley, like a pump.

This is certainly a good sign. However, this cooling phenomenon, while astonishing and providing a reprieve from rising temperatures, is unlikely to be enough to counter the overall effects of climate change. This study highlights the need to gather more high-elevation and long term data from the region to assess the broader impacts of this phenomenon.

This is especially important for the Himalayan region, where the glaciers feed twelve rivers, which in turn provide fresh water to almost 2 billion people living in sixteen countries.

The scientists used the Pyramid International Laboratory/Observatory climate station, located at a glacierized elevation of 5,050 meters (16,568 feet), along the southern slopes of Mount Everest and has been recording detailed meteorological data for almost 30 years.

The full study is available at Nature Geoscience

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I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.

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