Black carbon contributes to the melting of Himalayan glaciers and snowfields, warms the atmosphere at higher elevations and cools it at lower elevations, affecting atmospheric circulation patterns. It also reduces visibility to the point where snowy peaks are no longer visible from places whose livelihoods depend on selling mountain views to tourists. In addition, it contributes to changes in monsoon clouds and in the timing and intensity of rainfall, with potentially significant impacts on droughts, floods, landslides, hydropower, agriculture and drinking water availability.
While air pollution is severe in some of the larger cities in the plains, such as Delhi, Agra, and Dhaka, it can be as bad or worse in smaller cities within the HKH region, such as Kathmandu, Nepal. The mountains surrounding the Kathmandu Valley, and the airflow they create, confine its local emissions within the valley from early evening until late morning. Field studies during the first half of 2013 found concentrations of air pollutants several times above WHOs and Nepals own air quality standards for extended periods of time.
Emissions within the Kathmandu Valley are not the only source of its air pollution problem. There are also inputs from cooking fires, agricultural fires, and forest fires in the surrounding valleys and mountains, and more importantly, an inflow of air pollution up the Bagmati Valley from the south. While sewage from mountain cities flows down the rivers into the plains and across borders, a reverse flow of air pollution comes back up the mountain valleys. There are around 120 brick kilns within the Kathmandu Valley, less than 800 in all of Nepal, mostly in southern Nepal, but almost 23,000 in the two neighbouring Indian states of Uttar Pradesh and Bihar alone.
Air pollution crosses borders daily. Shutting down all of Nepals brick kilns will not stop the pollution arriving from the ones south of the border. Bhutan has no brick kilns. It imports its bricks as well as black carbon from brick kilns.
Creating effective air pollution policies to reduce peoples exposure to high levels of air pollution and to reduce its impacts on climate requires detailed scientific understanding of the links between sources and impacts, as well as regionally coordinated science-based policies. What fraction of the black carbon arriving on Yala Glacier in Langtang is from nearby households, from Kathmandu, from the Nepali Terai, or from India or beyond?
Effective policy making at the local and national levels requires detailed maps of emissions sources, atmospheric modeling systems that simulate the fate of emitted pollutants, connecting sources to impacts, as well as a network of measurement stations that provide real-time data to the public and policy makers and inputs to atmospheric models. It also requires free flow of data across borders, and regionally coordinated responses to high air pollution episodes. Ultimately, cleaning up air pollution in northern South Asia and reducing its impacts on the HKH region requires a strong push towards cleaner, less polluting technologies, include clean cooking, clean brick production and clean transportation.
Programme Coordinator - Atmosphere Initiative
International Centre for Integrated Mountain Development (ICIMOD)