A study of the Atmospheric Brown Cloud (ABC), a worrying phenomenon, according to scientists and environmentalists, by P. Bonasoni from the Institute of Atmospheric Sciences and Climate of the Italian National Research Council and his fellow researchers reveal the “the highest seasonal values of tempreture and relative humidity were registered during the monsoon season, which was also characterized by thick clouds present in about 80% of the afternoon hours.”
The research titled “Atmospheric Brown Clouds in the Himalayas” during the first two years of NCO-P’s establishment in 2006 and published in August 2010 says that brown cloud have a strong impact on the air quality, visibility and energy budget of the troposphere due to the components involved.
Bidya Banmali Pradhan, environment officer at the International Center for Integrated Mountain Development (ICIMOD), said that ABC are aerosols having more of anthropogenic constituents like sulphate, nitrogen oxides, and soot.
“These polluted aerosols are called ABC,” she said. “They get polluted by sulphate, Black Carbon (BC), nitrate, and organic particles.”
Ngamindra Dahal, a climate expert from the National Trust for Nature Conservation, said that pollutants like dust and fine particles from industrial activities have intensified, causing greater impacts at higher altitude.
“Before, the impact [like the hazy phenomenon] was seen occasionally, but now we have been observing that haze all year round,” he said.
And pollutants as such can affect and impact the solar intensity, atmospheric circulation, cloud formation, and condensation.
Pradhan of ICIMOD said black carbon is one of the major components of ABC, and in Nepal, the burning of biomass and fossil fuel help contribute to the increment of BC. The hazy phenomenon in the Everest region this summer has been the result of this. BC absorbs the light and dims the surface; and when the surface dims, it creates a hazy atmosphere.
“When the heat is absorbed by the clouds, solar radiation cannot reach the surface entirely,” Pradhan said.
In Bonasoni’s and his teammates’ analysis, “thick clouds were present in up to 50% of the cases in the afternoon during the pre-monsoon and rare during the winter season.”
According to environmentalists Pradhan and Dahal, the latter has been working in the climate sector for 15 years, the wind direction is transporting the pollutants from urban and industrial areas, hence creating the hazy impact in “pristine environment” like the Everest. Bonasoni’s report also points that the atmospheric condition of the Himalayas “can be influenced by transport of polluted air mass from South Asia and Indo Gangetic Plains (IGP)” due to the components such as fossil fuel combustion and biomass burning that favors the formation of ABC.
But the effects of ABC could be more than just the haze in the atmosphere.
Though the components of ABC are short-lived, the other gases like carbon monoxide, volatile organic compounds, and nitrogen oxide present in the ABC triggers the formation of ozone precursor gases, which is a very strong greenhouse gas, Pradhan said.
“The atmospheric ozone has major impacts on crops since many of the plants are ozone sensitive,” she said.
Bonasoni’s paper also brings forth the point that the IGP in South Asia that include regions like eastern Pakistan, India, Bangladesh, and Myanmar are the “brown cloud hot spots,” and meteorological conditions in these places also promote an ideal environment for wildfires, which can emit more carbonaceous aerosol and ozone precursors in the atmosphere.
As scientists have discovered the impacts of ABC on human health, agriculture, hydrological cycle, and the atmosphere at large, not enough studies have been done to correlate its impact on the glacial retreat in the Himalayas, Pradhan said.
“In terms of glacial retreat, we are only predicting that this [the BC present in ABC] could be one of the causes, but we haven’t been able to give the exact data figures,” she added.
Pradhan said the Nepal Academy of Science and Technology (NAST) should step in and collaborate on this issue. No one was available to comment from NAST on this particular issue despite several attempts made by The Week for the same.
“It’s high time for NAST to take a lead,” Pradhan said.
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