Dual role as air pollutant and warming agent makes black carbon a neglected player in policy

Subject: Environment

Section: Pollution

Context:

A policy brief from the Center for Study of Science, Technology and Policy (CSTEP) and Clean Air Fund suggests that increasing black carbon in the atmosphere is causing extreme rainfall in Asian countries like India and China, and shifting rain clouds northwards.

Details:

Black carbon, a significant component of fine particulate matter PM2.5, is emitted from incomplete combustion of biomass, fossil fuels, and waste.
Despite its short atmospheric lifespan of a few weeks, it has a warming impact up to 1,500 times stronger than CO2 per unit of mass.
The report emphasizes black carbon‘s role in accelerating snow and ice melt in the Arctic, Himalayas, and Andes, disrupting monsoon patterns in West Africa and India, and exacerbating dangerous heat waves.
Although crucial, black carbon is often overlooked in climate change discussions due to disputes over its sources and uncertainties about its warming contribution.
Its dual nature as both a climate and air pollutant leads to a lack of full ownership in climate and health agendas.
The policy brief, released during COP28 in Dubai in December 2023, aims to highlight black carbon’s impact on both air pollution and climate change, such as the faster melting of glaciers and sea ice, and the need to include it in climate action.
Currently, air quality regulations do not explicitly target black carbon, leaving its emissions uncontrolled in climate frameworks and air quality regulations.

Affecting the monsoon:

The report emphasizes that black carbon significantly alters regional precipitation patterns and slows down the hydrological cycle, leading to drier conditions.
Its impact on global hydrological sensitivity is nearly double that of CO2.
Black carbon emissions are linked to extreme rainfall events and flooding in China and India and are also thought to contribute to the early onset of the monsoon.
Black carbon affects atmospheric thermodynamics, impacting convective potential and seasonal rainfall trends in India.
Its ability to absorb sunlight leads to reduced solar radiation at the surface and simultaneous atmospheric warming, thereby affecting both surface and atmospheric temperatures and, consequently, monsoon circulation.

Forest fire a big contributor:

There is a concern over the increasing role of forest fires in black carbon emissions.
Globally, wildfires contribute more to black carbon emissions than transportation. While transportation is often considered a major urban source of black carbon, with on-road diesel emissions contributing about a quarter and residential biomass fuel about 35% of anthropogenic black carbon, wildfires generally account for about one-third of global black carbon emissions, surpassing transportation.
Studies in Uttarakhand’s Bhagirath-Kharak Glacier and Gangotri Glacier Valley indicate a significant role of wildfires and biomass burning in the high rate of black carbon influx in the Central Himalayas.

What India needs to do?

India should include black carbon in its National Clean Air Programme (NCAP 2.0) and Nationally Determined Contributions (NDCs) to address its polluting and warming aspects.