Skip to main content

Aerosols are already released into the atmosphere by human activities at large scales, primarily through combustion of organic matter and fossil fuels.

Summary​

Human activities release significant amounts of aerosols into the atmosphere, mainly through combustion processes. These solid or liquid particles differ from greenhouse gases like CO₂ and methane which are gaseouse gaseous. Major anthropogenic sources include industrial activities and burning of organic matter/fossil fuels, producing aerosols like black carbon, sulfates, nitrates, and mineral dust. Sulfate aerosols form from sulfur dioxide emissions (105.4 million metric tons annually in 2014), with 98% originating from human activities. These particles can impact ozone depletion, acid rain formation, and human health. Sulfate aerosols are particularly relevant for potential climate intervention strategies like stratospheric aerosol injection, though their use carries uncertainties.

In addition to natural sources such as volcanic eruptions, aerosols can be introduced into the atmosphere by human activities. Aerosols are any particle that is solid or liquid that is suspended in a gas medium. From this definition, greenhouse gases like CO₂ and methane are not considered aerosols as they are in their gaseous state. As aerosols are non-gaseous and are instead particles in a solid or liquid state, they have difficulty entering into the atmosphere naturally and usually require an external driving force. It is for this reason that most anthropogenic aerosols are the result of some sort of burning or combustion 1.

Common anthropogenic aerosols​

Anthropogenic aerosols can be produced from industrial processes such as mining and concrete production, as well as from combustion. Aerosols produced from mining typically consist of fine mineral dusts which are caught by the wind and can travel long distances. Combustion, which is the largest source of anthropogenic aerosols, is usually derived from the combustion of organic matter or the combustion of fossil fuels. Practices such as slash and burn agriculture introduce organic aerosols such as black carbon or partially combusted organic matter which is lifted into the atmosphere by the convection generated by the heat of combustion 2. Some common anthropogenic aerosols include:

  • Black Carbon
  • Sulfate
  • Nitrate
  • Organic compounds, such as those found in photochemical smog
  • Mineral dust

Sulfate aerosols​

Sulfate aerosols are one of the most common aerosols released into the atmosphere, with an estimated global sulfur dioxide (SO₂) emission of 105.4 Tg per year (equivalent to 1.054 × 10¹¹ kg per year) in 2014 3. Of these sulfur dioxide emissions, 98% is estimated to originate from anthropogenic sources 3. Sulfur dioxide is not itself an aerosol, but rather a gas that reacts with other particles in the atmosphere to form sulfate aerosols. Sulfate aerosols have significant negative impacts on the environment and health including:

Aerosols frequently considered to have the greatest potential for Stratospheric Aerosol Injection (SAI) are sulfate aerosols, as they are somewhat of a known quantity, already present and being emitted into the lower atmosphere. That is not to say that there isn't still an enormous level of uncertainty associated with SAI in general. A large source of sulfate aerosol emissions is from international shipping, which accounted for 16% of sulfate emissions in 2014 3. Due to the wide area of dispersion and regularity of maritime sulfur dioxide emissions, they have had a noted cooling effect on the earth's albedo and global temperatures. However, this cooling effect has diminished in the past decade as sulfur dioxide emissions have decreased due to international shipping regulations 4.

Sources​

Footnotes​

  1. Boucher, O. (2015). Atmospheric aerosols. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-9649-1_2 ↩

  2. Prather, K. A., & Hatch, C. D. (2008). Analysis of atmospheric aerosols. Annual Review of Analytical Chemistry, 1, 377–404. https://doi.org/10.1146/annurev.anchem.1.031207.113030 ↩

  3. Zhong, Q., Shen, H., Yun, X., Chen, Y., Ren, Y., Xu, H., Shen, G., Du, W., Meng, J., Li, W., Ma, J., & Tao, S. (2020). Global emissions of major organic compounds from anthropogenic sources. Environmental Science & Technology, 54(11), 6508–6517. https://doi.org/10.1021/acs.est.9b07696 ↩ ↩2 ↩3

  4. Yuan, T., Song, H., Oreopoulos, L., Wood, R., Bian, H., Breen, K., Chin, M., Yu, H., Barahona, D., Meyer, K., & Platnick, S. (2024). Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming. Communications Earth & Environment, 5(1), Article 281. https://doi.org/10.1038/s43247-024-01442-3 ↩