Letter | Published:

Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols

Nature volume 409, pages 695697 (08 February 2001) | Download Citation



Aerosols affect the Earth's temperature and climate by altering the radiative properties of the atmosphere. A large positive component of this radiative forcing from aerosols is due to black carbon—soot—that is released from the burning of fossil fuel and biomass, and, to a lesser extent, natural fires, but the exact forcing is affected by how black carbon is mixed with other aerosol constituents. From studies of aerosol radiative forcing, it is known that black carbon can exist in one of several possible mixing states; distinct from other aerosol particles (externally mixed1,2,3,4,5,6,7) or incorporated within them (internally mixed1,3,7), or a black-carbon core could be surrounded by a well mixed shell7. But so far it has been assumed that aerosols exist predominantly as an external mixture. Here I simulate the evolution of the chemical composition of aerosols, finding that the mixing state and direct forcing of the black-carbon component approach those of an internal mixture, largely due to coagulation and growth of aerosol particles. This finding implies a higher positive forcing from black carbon than previously thought, suggesting that the warming effect from black carbon may nearly balance the net cooling effect of other anthropogenic aerosol constituents. The magnitude of the direct radiative forcing from black carbon itself exceeds that due to CH4, suggesting that black carbon may be the second most important component of global warming after CO2 in terms of direct forcing.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    , , , & General circulation model calculations of the direct radiative forcing by anthropogenic sulfate and fossil-fuel soot aerosol. J. Clim. 10, 1562–1577 (1997).

  2. 2.

    & Global sensitivity studies of the direct radiative forcing due to anthropogenic sulfate and black carbon aerosols. J. Geophys. Res. 103, 6043–6058 (1998).

  3. 3.

    , , & Estimation of the direct radiative forcing due to sulfate and soot aerosols. Tellus B 50, 463–477 (1998).

  4. 4.

    , , & Construction of a 1°×1° fossil fuel emission data set for carbonaceous aerosol and implementation and radiative impact in the ECHAM4 model. J. Geophys. Res. 104, 22137–22162 (1999).

  5. 5.

    et al. Climate forcings in the industrial era. Proc. Natl Acad. Sci. USA 95, 12753–12758 (1998).

  6. 6.

    , & Climate forcing by carbonaceous and sulfate aerosols. Clim. Dyn. 14, 839–851 (1998).

  7. 7.

    A physically-based treatment of elemental carbon optics: Implications for global direct forcing of aerosols. Geophys. Res. Lett. 27, 217–220 (2000).

  8. 8.

    Development and application of a new air pollution modeling system - II. Aerosol module structure and design. Atmos. Environ. 31, 131–144 (1997).

  9. 9.

    et al. Internal mixture of sea salt, silicates, and excess sulfate in marine aerosols. Science 232, 1620–1623 (1986).

  10. 10.

    et al. Influence of sea-salt on aerosol radiative properties in the Southern Ocean marine boundary layer. Nature 395, 62–65 (1998).

  11. 11.

    , , & Soot and sulfate aerosol particles in the remote marine troposphere. J. Geophys. Res. 104, 21685–21693 (1999).

  12. 12.

    , , , & Chemical apportionment of aerosol column optical depth off the mid-Atlantic coast of the United States. J. Geophys. Res. 102, 25293–25303 (1997).

  13. 13.

    , & Aerosol properties and radiative effects in the United States East Coast haze plume: An overview of the tropospheric aerosol radiative forcing observational experiment (TARFOX). J. Geophys. Res. 104, 2213–2222 (1999).

  14. 14.

    et al. Direct observations of aerosol radiative forcing over the tropical Indian Ocean during the January-February 1996 pre-INDOEX cruise. J. Geophys. Res. 103, 13827–13836 (1998).

  15. 15.

    et al. A model for the natural and anthropogenic aerosols over the tropical Indian Ocean derived from Indian Ocean Experiment data. J. Geophys. Res. 104, 27421–27440 (1999).

  16. 16.

    , , & Measurements of irradiance attenuation and estimation of aerosol single scattering albedo for biomass burning aerosols in Amazonia. J. Geophys. Res. 103, 31865–31878 (1998).

  17. 17.

    et al. Single-scattering albedo of smoke retrieved from the sky radiance and solar transmittance measured from ground. J. Geophys. Res. 103, 31903–31923 (1998).

  18. 18.

    , & Characterization of tropospheric aerosols over the oceans with the NOAA advanced very high resolution radiometer optical thickness operational product. J. Geophys. Res. 102, 16889–16909 (1997).

  19. 19.

    et al. (eds) Climate Change 1995, The Science of Climate Change (Cambridge University Press, New York, 1996).

  20. 20.

    , , , & Global warming in the twenty-first century: An alternative scenario. Proc. Natl Acad. Sci. 97, 9875–9880 (2000).

  21. 21.

    et al. Costs of multigreenhouse gas reduction targets for the USA. Science 286, 905–906 (1999).

Download references


This work was supported by the NASA New Investigator Program, the NSF, the David and Lucile Packard Foundation, and Hewlett-Packard.

Author information


  1. Department of Civil & Environmental Engineering, Stanford University, Stanford, California 94305-4020, USA

    • Mark Z. Jacobson


  1. Search for Mark Z. Jacobson in:

Supplementary information

About this article

Publication history






Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.