Dirty snow defrosts Nepal’s mountains

Greenhouse gas buildup in the atmosphere is set to raise global average temperatures by at least 2°C above pre-industrial levels by 2050, and this is still the main reason Nepal’s glaciers are receding and shrinking. But controlling soot particles and reducing dust in the air could slow the process.

The Nature study found that black carbon particles have a larger snow albedo darkening effect than dust because it is darker. But dust contributes more to melting because there is up to 1,000 times more of it than soot.

“Temperatures are increasing faster in the Himalaya, this makes weather conditions more unstable prompting long distance transport of dust and other particles more likely,” explains climate scientist Binod Pokharel. The new study now confirms that the role of dust deposit in melting Himalayan ice is greater than previously thought.

Now that the monsoon is here, people in Kathmandu Valley find it easier to breathe since the air quality index (AQI) is better. But vehicular emissions and brick kiln smoke keep the concentration of suspended soot particles in the air at unhealthy levels.

Dirtier air increases the incidence of chronic obstructive pulmonary disease (COPD), lung cancer, bronchitis, stroke, mental retardation and congenital heart defects. Particles less than 2.5 microns are especially dangerous because they can cross the air-blood barrier in the lung capillaries.

Previous studies on Langtang Glacier showed that while global warming was still the main cause of melting, up to 20% of the defrosting was due to snow darkening because of soot deposition.

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