The Hindu Kush Himalayan (HKH) region has received much attention as the source of rivers that supply water to 1.3 billion people downstream. It has received far less attention for its role as the recipient of the air pollution originating in the plains.
Across northern South Asia during the dry season, individual plumes from hundreds of millions of cooking fires, tens of millions of diesel vehicles, generators and pump sets, as well as tens of thousands of brick kilns merge together into one thick brown haze layer that extends across international borders from Pakistani Punjab to Bangladesh, penetrating deep into Himalayan valleys. A major constituent of this haze is black carbon.
Black carbon is a carcinogen and has major impacts on people’s health. It is also a ‘short-lived climate pollutant’ (SLCP) – an air pollutant that has significant impacts on local and regional climate. Unlike the greenhouse gas carbon dioxide (CO2), which, once emitted, stays in the atmosphere for centuries impacting global climate, SLCPs have atmospheric lifetimes of days to months.
The good news is that shutting down the sources of SLCPs reduces their climate impact within days to months. Their short lifetime also means that they do not have time to mix uniformly around the globe, and that their greatest impact is near their sources. The bad news is that the HKH region is near a major source region for black carbon: the Indo-Gangetic Plains, where more than half a billion people live along the Indus, Ganges, and Brahmaputra rivers and their tributaries. While globally black carbon has the second biggest impact on climate after CO2, its impact in northern South Asia is much bigger than its global average.
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Across northern South Asia during the dry season, individual plumes from hundreds of millions of cooking fires, tens of millions of diesel vehicles, generators and pump sets, as well as tens of thousands of brick kilns merge together into one thick brown haze layer that extends across international borders from Pakistani Punjab to Bangladesh, penetrating deep into Himalayan valleys. A major constituent of this haze is black carbon.
Black carbon is a carcinogen and has major impacts on people’s health. It is also a ‘short-lived climate pollutant’ (SLCP) – an air pollutant that has significant impacts on local and regional climate. Unlike the greenhouse gas carbon dioxide (CO2), which, once emitted, stays in the atmosphere for centuries impacting global climate, SLCPs have atmospheric lifetimes of days to months.
The good news is that shutting down the sources of SLCPs reduces their climate impact within days to months. Their short lifetime also means that they do not have time to mix uniformly around the globe, and that their greatest impact is near their sources. The bad news is that the HKH region is near a major source region for black carbon: the Indo-Gangetic Plains, where more than half a billion people live along the Indus, Ganges, and Brahmaputra rivers and their tributaries. While globally black carbon has the second biggest impact on climate after CO2, its impact in northern South Asia is much bigger than its global average.
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