What is Brown Carbon (BrC)? Why it is in

  Dec 29, 2016

Among the many contributors to climate change are aerosols in the atmosphere. These tiny particles suspended in the air come from many sources, some natural and some man-made. Some aerosols are organic (containing carbon), while others are inorganic. Most aerosols reflect sunlight, and some also absorb it. Many of these nanoparticles have severe health effects in addition to climate effects.

Black carbon  particles (a component of soot) originating from combustion processes have been known for some time to absorb sunlight and warm the atmosphere.
More recently, “brown carbon” (light-absorbing organic carbon) has attracted interest as a possible cause of climate change. This class of organic carbon, known for its light brownish color, absorbs strongly in the ultraviolet wavelengths and less significantly going into the visible. Types of brown carbon include tar materials from smoldering fires or coal combustion, breakdown products from biomass burning, a mixture of organic compounds emitted from soil, and volatile organic compounds given off by vegetation.
Brown carbon contributes +0.25 W m^-2 or about 19% of the total atmospheric absorption by anthropogenic aerosols, while 72% is attributed to black carbon and 9% is due to the coating effect of sulfate and organic aerosols on black carbon. Brown carbon needs to be considered in global climate simulations.
 
A study of IIT Kanpur has highlighted that Brown Carbon has the potential to warm atmosphere by absorbing light. When compared to Black Carbon, Brown Carbon has 10 times more mass; Black Carbon has 50 times more absorption capacity than BrC. Both of them are absorbers, contributing in the warming of atmosphere.