Research Changes View on Brown Carbon Effects


Researchers at the Los Alamos National Laboratory have successfully found a method for quantifying the perplexing nature of brown carbon. The previous view was that brown carbon had a cooling effect with respect to climate change, but research has shown the opposite. As a result, wildfires around the world are possibly a bigger factor in climate warming than estimated.

A senior Los Alamos climate scientist, Mavendra Dubey, described brown carbon as frustrated black carbon that is produced when wood has not fully cooked.  According to Dubey, wildfires emit a plethora of toxic particles that can affect the climate on earth. What is known for sure is that the smoke produced from these fires is toxic to humans. What is unclear to scientists is the specific effect these toxins have on climate.

For many years, scientists have been delving into the complexity of brown carbon. To better understand climate change, factors like brown carbon need to be quantifiable, otherwise, their impact on the atmosphere and environment could be underestimated. The rise in temperatures over recent years has become a major concern. The Climate Action Plan, though under scrutiny, shows that awareness of all possible factors is important to create an effective plan that can positively affect earth.

The more easily understood compound known as black carbon absorbs sunlight at all wavelengths, making it a potent warmer. However, black carbon has an organic carbon twin that is emitted in smoke at the same time, changing its impact. The organic carbon reflects sunlight, which means that the two basically cancel each other out. Brown carbon aerosols have been a difficult issue for scientists, because it comes mixed in with other organic materials. The carbon is volatile and has many variables that make it hard to identify.

Through the research conducted at Los Alamos, scientists determined that brown carbon has similarities with black carbon, but whereas black carbon absorbs sunlight at all wavelengths, brown carbon absorbs sunlight at short blue wavelengths. In past research, scientist have viewed brown carbon as an organic material, believing that it had a cooling effect on climate change. Many models have even tested theories and collected data about fire emission under this idea.

The particle’s ability to reflect or absorb solar radiation is a key to understanding its overall effect. Some particles intercept sunlight before it hits Earth’s surface, therefore heating the atmosphere while cooling the earth below it. Aside from warming the atmosphere, this may also lead to reduction of cloud coverage and rainfall. Black carbon has been accounted for in this respect, but now brown carbon can finally be added to data.

The modelers and researchers who formed the Los Alamos team worked closely together to create controlled model experiments that could test these ideas about brown carbon. The team used heat to carefully manipulate particles emitted by globally important fuels. This process allowed them to separate the volatile components in order to analyze the least volatile fraction. That fraction was found to absorb far more light than the volatile fraction and would be more likely to travel globally like black carbon.

The team believes that these findings show that brown carbon aerosols have a global significance that should be taken into account. It is the missing warming agent that should be added to climate models so that it can be effectively treated. The research team hopes that the views on brown carbon’s effect will change and offer more information to those continuing work on climate.

By Kamille Dawkins


Los Alamos National Laboratory
Atmospheric Chemistry and Physics

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