Policy measures for air quality and climate change

This tools was developed as part of a larger international project to study the long range transport of air pollutants. We demonstrate this tool here using ozone.

Ozone: a pollutant and a greenhouse gas

In the lower part of the atmosphere, ozone (O3) is a secondary air pollutant, formed from chemical reactions of other emitted primary pollutants (nitrogen oxides, hydrocarbons, and methane). The source of these pollutants can be both man-made (e.g. energy production and transportation) and natural (soils, vegetation).

At the surface of the earth, ozone contributes to poor air quality. It can damage people’s health, mainly through respiratory illnesses (Jerrett et al., 2009) and has a negative impact on crops and natural ecosystems (Fowler et al., 2009). However, ozone in the lower atmosphere can also influence the Earth’s climate by acting as a greenhouse gas and increasing surface temperatures (Myhre et al., 2013).

New Study

A new tool developed by scientists at the Met Office Hadley Centre, in collaboration with Lancaster University, enables assessment of the impact of future changes in air pollutant emissions on air quality and climate.

The tool uses input from multiple chemistry models to develop a relationship that describes how ozone responds to a change in emissions of primary air pollutants and methane gas. By using ozone concentrations as an indicator of surface air quality, the impact of these changes can be calculated. Additionally, since ozone is also a greenhouse gas, the tool is able to assess how changes in ozone in the atmosphere alter its interaction with the Earth’s climate. Different emission scenarios can then be used with the tool to predict how ozone concentrations will respond in the future.

A paper published in Atmospheric Chemistry and Physics on 28th June 2018 (Turnock et al., 2018), uses this assessment tool to examine the impact from ozone on future air quality and climate change  in three different greenhouse gas and air pollutant emissions pathways (Klimont et al., 2017, 2018). The different pathways considered are:

  • Future implementation of current environmental legislation (CLE).
  • An energy and climate scenario on top of current legislation, targeting 2 °C in which emissions of air pollutants and methane are reduced (CLIM)
  • Introduction of Maximum Technical Feasible Reductions, assuming no economic or technological constraints (MTFR)

Under current legislation (CLE), future increases in surface O3 are predicted to occur across all regions by 2050 and will have a warming impact on climate. This indicates that current legislation is ineffective at limiting the future degradation of regional air quality and enhancement of near-term climate warming from ozone. Implementing a climate policy scenario on top of current legislation (CLIM) reduces the impact to both surface air quality and climate when compared to CLE.  However, large benefits to air quality (in terms of reducing surface O3 concentrations) and climate can be achieved by implementing all possible technological measures (MTFR). When developing new emission pathways, it is important to consider the impact on both air quality and climate.

The tool developed in this study is a quick way of providing an initial assessment of the impact of emissions changes on surface air quality and climate from different emission policy options, without the need for running complex models. Future applications include analysing new emissions pathways, as well as extending it to consider impacts such as human health and crop damage.


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Jerrett, M., Burnett, R. T., Pope, C. A., Ito, K., Thurston, G., Krewski, D., Shi, Y., Calle, E. and Thun, M.: Long-Term Ozone Exposure and Mortality, N. Engl. J. Med., 360(11), 1085–1095, doi:10.1056/NEJMoa0803894, 2009.

Klimont, Z., Kupiainen, K., Heyes, C., Purohit, P., Cofala, J., Rafaj, P., Borken-Kleefeld, J. and Schöpp, W.: Global anthropogenic emissions of particulate matter including black carbon, Atmos. Chem. Phys, 17, 8681–8723, doi:10.5194/acp-17-8681-2017, 2017.

Klimont, Z., Hoglund-Isaksson, L., Heyes, C., Rafaj, P., Schopp, W., Cofala, J., Purohit, P., Borken-Kleefeld, J., Kupiainen, K., Kiesewetter, G., Winiwarter, W., Amann, M., Zhao, B., Bertok, I. and Sander, R.: Global scenarios of air pollutants and methane: 1990-2050, in prep., 2018.

Myhre, G., Shindell, D., Breon, F.-M., Collins, W., Fuglestvedt, J., Huang, J., Koch, D., Lamarque, J.-F., Lee, D., Mendoza, B., Nakajima, T., Robock, A., Stephens, G., Takemura, T. and Zhang, H.: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernemental Panel on Cliamte Change, edited by T. F. Stocker, D. Qin, G.-K. Plattner, M. Tignore, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex, and P. M. Midgley, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA., 2013.

Turnock, S. T., Wild, O., Dentener, F. J., Davila, Y., Emmons, L. K., Flemming, J., Folberth, G. A., Henze, D. K., Jonson, J. E., Keating, T. J., Kengo, S., Lin, M., Lund, M., Tilmes, S. and O’Connor, F. M.: The impact of future emission policies on tropospheric ozone using a parameterised approach, Atmos. Chem. Phys., 18(12), 8953–8978, doi:10.5194/acp-18-8953-2018, 2018.