Brown Carbon Changes Environment, Climate
Review identifies gaps to be filled to quantify brown carbon's impact on environment, climate
Brown carbon is an important contributor to air pollution and climate change. A comprehensive review article published in 2015 focusing on atmospheric chemistry of this aerosol paves the way for more accurate climate models as well as strategies to curb negative effects.
Results: Researchers from Pacific Northwest National Laboratory and University of California, Irvine published an invited comprehensive manuscript reviewing the chemistry of atmospheric brown carbon -- a type of organic aerosol characterized by an absorption spectrum that smoothly increases from visible to ultraviolet wavelengths. In the review manuscript, the authors summarized field observations, laboratory experiments, and modeling studies describing the role of brown carbon in air pollution and climate forcing -- the difference of sunlight absorbed by earth and energy radiated back to space.
Why It Matters: Brown carbon may be a key contributor to air pollution and climate change. By reviewing evidence on physical and chemical properties and prioritizing topics for future research, the article paves the way for more accurate climate model predictions. In addition, it assists in designing strategies to curb negative effects of brown carbon on climate and environment.
Methods: Current climate modeling often neglects brown carbon because researchers assume black carbon and mineral dust are the two significant types of light-absorbing aerosols on the global scale. In the article, the scientists reviewed the evidence and impact of light-absorbing organic compounds in the atmosphere, the current methods for characterizing such aerosols, and discussed the laboratory studies that modeled brown carbon systems.
What's Next? The team recommended topics for future research examining effects of brown carbon on climate and environment. Because the accuracy of atmospheric and climate models is limited by a lack of information as to the chemical properties of brown carbon, more basic research is needed to understand the most important properties and parameters to include in these models.
Sponsors: U.S. Department of Commerce, National Oceanic and Atmospheric Administration through the Climate Program Office's AC4 program, awards NA13OAR4310066 (PNNL) and NA13OAR4310062 (UCI). Additional support for previous and ongoing research projects in the authors' groups has been provided by the U.S. Department of Energy's (DOE) Office of Biological and Environmental Research (BER) through its sponsorship of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL); DOE-BER Atmospheric System Research program (A.L.); DOE's Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences (J.L.); U.S. National Science Foundation grants AGS-1227579, CHE-0909227, and MRI-0923323 (S.A.N.); Laboratory Directed Research and Development funds of PNNL (A.L.).
User Facilities: Many previous and ongoing research projects were conducted at locations around the world and used U.S. Department of Energy national scientific user facilities such as EMSL, the Atmospheric Radiation Measurement Climate Research Facility and the Advanced Light Source at Lawrence Berkeley National Laboratory.
Reference: Laskin A, J Laskin and S Nizkorodov. 2015. "Chemistry of Atmospheric Brown Carbon." Chemical Reviews 115(10):4335-4382. DOI: 10.1021/cr5006167