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ESA Climate Change Initiative (CCI) for Aerosol and Ozone Essential Climate Variables
Tropospheric ozone (O₃) trends are nonlinearly influenced by near-surface anthropogenic emissions of carbon monoxide (CO), volatile organic compounds (VOCs), and nitrogen oxides (NOₓ).
As part of its Climate Change Initiative (CCI) programme, the European Space Agency (ESA) recently launched a project coordinated at BIRA-IASB, aiming to generate robust, long-term records of key short-lived atmospheric species, precursors of ozone and aerosol particles.
Six species are under focus:
- NO2
- HCHO
- SO2
- CHOCHO
- CO
- NH3
By integrating data from multiple satellite missions—including GOME, SCIAMACHY, OMI, and TROPOMI— harmonized and consistent Climate Data Records (CDRs) of HCHO and NO2 spanning more than two decades are being produced. Significant improvements in retrieval algorithms have enhanced the accuracy, precision, and the long-term stability of the data sets.
Validation against ground-based measurements from FTIR and MAX-DOAS demonstrates reduced biases in HCHO observations, resulting in more reliable data for climate monitoring and trend analysis.
Trends analysis over 15 years
The figures llustrate trend analyses based on the recently produced HCHO and NO₂ CCI CDRs, derived from OMI and TROPOMI measurements.
Notable regional trends emerge, with southern Asia—particularly India—exhibiting the most pronounced increases in HCHO. Central Africa, parts of central Brazil, and northern Australia also show rising trends. In contrast, HCHO levels have declined in the southeastern United States, Europe, eastern Asia, and southern Australia.
For NO₂, decreasing trends are observed in western and southern Europe, North America, Japan, and Indonesia. Certain eastern regions of China also show declines, though other areas continue to experience rising NO₂ levels. India, southeastern Asia, and parts of the Middle East display increasing NO₂ trends.
The observed decreases in surface ozone over the northeastern United States and Europe are attributed to simultaneous reductions in NO₂ and HCHO, a result of effective air pollution mitigation policies implemented over the past two decades [Elshorbany et al., 2024, Fadnavis et al., 2024].
The CCI data is provided in user-friendly formats that optimize download efficiency, ensuring accessibility without requiring large file transfers. This streamlined distribution enhances usability, making these critical climate datasets widely available for climate and atmospheric research.
Links
- ESA Climate Initiative Precursors for Aerosols and Ozone
- International Tropospheric Ozone Assessment
References
- Elshorbany, Y., Ziemke, J., Strode, S., Petetin, H., Miyazaki, K., De Smedt, I., Pickering, K., Seguel, R., Worden, H., Emmerichs, T., Taraborrelli, D., Cazorla, M., Fadnavis, S., Buchholz, R., Gaubert, B., Rojas, N., Nogueira, T., Salameh, T., and Huang, M.: Tropospheric Ozone Precursors: Global and Regional Distributions, Trends and Variability, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-720, 2024.
- Fadnavis, S., Elshorbany, Y., Ziemke, J., Barret, B., Rap, A., Chandran, P. R. S., Pope, R., Sagar, V., Taraborrelli, D., Le Flochmoen, E., Cuesta, J., Wespes, C., Boersma, F., Glissenaar, I., De Smedt, I., Van Roozendael, M., Petetin, H., and Anglou, I.: Influence of nitrogen oxides and volatile organic compounds emission changes on tropospheric ozone variability, trends and radiative effect, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-3050, 2024.
