Scopes and Perspectives Related to the South American Ozone Assessment Report

Rodrigo Seguil ^dadCharlie Opazu ^dad and lucas castillo ^dad
(a) Centre for Climate Science and Resilience
(b) Department of Geophysics, Faculty of Physical and Mathematical Sciences, University of Chile

edition: Jose Barraza, Scientific Communication CR2

• Surface ozone trends in major South American cities have increased or remained stable over the past decade.
• In the capital region, surface-level ozone has increased since 2017.

context setting

Tropospheric Ozone Assessment Report (pulls)developed by the International Atmospheric Chemistry Group. (Ijak)Provides an up-to-date scientific assessment of the global distribution and trends of tropospheric ozone, that is, ozone from the planet’s surface to approximately 10 to 15 kilometers above sea level.

TOAR Phase 1 (2014-2019) An open-access database with easily accessible web services has been produced to evaluate ozone measurements at all available observing sites in the world, providing the scientific community with the first global view of surface ozone based on observations.

TOAR is currently in its second phase. (TOAR-II, 2020-2025)More than 150 researchers from 31 countries are participating in it, who have formed 16 working teams.^[1]to update the global distribution and trends of tropospheric ozone, this time including its precursors (gases that produce ozone through chemical reactions). As in Phase I, TOAR-II aims to measure the effects of tropospheric ozone on climate, human health and vegetation.

State of knowledge

Recent research indicates that the global load of tropospheric ozone has increased by 45% from 1850 to the present, due to anthropogenic precursor emissions. (Soba et al., 2021)In addition, surface ozone has increased by 32 to 71% (highly uncertain data) in the atmosphere of rural areas in the Northern Hemisphere compared to historical observations (1896-1975). (Tarasik et al., 2019)Since the mid-1990s, the abundance of ozone in the free troposphere (between about 3 and 12 kilometers altitude) of the atmosphere has increased.^[2] Between 1 and 4 nmol^-1 per decade in most mid-latitude regions of the Northern Hemisphere, and between 1 and 5 nanomoles.^-1 For each decade within the tropics (high confidence data) (Gulev et al., 2021).

In the case of the Southern Hemisphere, estimation of ozone trends is hampered by limited coverage of monitoring stations, while tropospheric column ozone observations since the mid-1990s indicate increases with average confidence of less than 1 nmol mol.^-1 per decade in mid latitudes (Cooper et al., 2020; Jollif et al., 2021).

south america

In the global context, the scientific community considers South America to be an understudied region, where ozone trend estimates are rarely comprehensively considered. For this reason, Working Group on Tropospheric Ozone Precursors Part of its efforts focused on estimating trends in surface ozone and its precursors since the beginning of the 21st century in this region of the world. The results were published in a special issue of the journal CopernicusIn 2024, let us conclude the following:

Surface ozone trends in major South American cities monitored have increased or remained stable, with no evidence of decrease over the past decade.
The upward trends found can be attributed to photochemical systems that efficiently convert anthropogenic precursors into chemicals that favor ozone accumulation.
The results point to what we will call a “climate penalty” for ozone. This means that extreme events tend to cause an increase in ozone, which worsens air quality. In the case of Chile, the climate conditions were favorable for the spread of forest fires, which caused the emission of ozone precursors. In the case of southern Brazil, this penalty is associated with widespread heat waves that were able to increase the formation of tropospheric ozone (as we saw in Previous CR2 analysisThe higher the temperature, the more ozone there is in the atmosphere.

Related results for Chile

• In the metropolitan area, surface ozone decreased by 2 nmol mol-1 per decade from 1997 to 2017 (very high confidence data). However, as of 2017, the ozone trend increased by 0.6 nmol mol-1.^-1Annually (with high confidence), representing a cumulative total of 3 nmol/mol.^-1 In five years. Thus, in the past five years there has been a setback equivalent to 20 years of progress in reducing ozone (Figure 1). This increase in just five years is partly explained by warmer summers, ozone precursors emitted by wildfires, Impact of the pandemic In anthropogenic emissions and varying control of nitrogen oxides and volatile organic compounds (represented in Figure 1 by carbon monoxide), among other variables.
• The town of Los Andes showed the highest levels of risk due to short- and long-term ozone exposure, with 88 and 58 nmol m.^-1respectively. These values ​​far exceeded the short- and long-term limits recommended by the World Health Organization, set at 51 and 31 nmol/mol.^-1respectively (WHO, 2021).
• The Tololo station, located in the Coquimbo region at an altitude of 2.2 km, is one of the few stations in South America with a long enough time series to assess changes in the ozone baseline. Here, an increase in ozone was observed between 2006 and 2014 with a cumulative total of 2 nmol m^-1which, from a regional and hemispheric perspective, signals changes in the baseline level of ozone in the Southern Hemisphere troposphere.

Development Activities: Regional Assessment of Tropospheric Ozone in South America

As a means of continuing to improve information literacy and confidence in South America, the TOAR-II Steering Committee agreed to complete a specific assessment of this region.^[3]Its objectives are to fill information gaps derived from low coverage of surface measurements by using satellite observations and regional models as well as reporting risks and key findings with their respective uncertainty estimates.

References

Cooper, O.R., Schultz, M.G., Schröder, S., Chang, K.L., Gaudel, A., Benítez, G.C., Cuevas, E., Fröhlich, M., Galbally, I.E., Molloy, S., Kubistin, D., Lu, S., Spain, G.T., Spangl, W., Steinbacher, M., Tarasick, D., Thouret, V., & Xu, X. (2020). Multidecadal trends in surface ozone at globally distributed remote locations. Elementa, 8, 23. https://doi.org/10.1525/elementa.420.

Jolliffe, S. K., P. W. Thorne, J. Ahn, F. J. Dentiner, C. M. Dominguez, S. Gerland, D. Jong, D. S. Kaufman, H. C. Namchi, J. Quaas, J. A. Rivera, S. Sathyendranath, S. L. Smith, P. Trewin, K. von Schuckmann, and R. S. (2021). Changing state of the climate system. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 287-422, doi:10.1007/2007-017-0171 10.1017/9781009157896.004.

World Health Organization (WHO). 2021. Global Air Quality Guidelines. Particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide, carbon monoxideWorld Health Organization, Geneva, ISBN 978-92-4-003422-8, ISBN 978-92-4-003421-1.

Seguel, R. J., Castillo, L., Opazo, C., Rojas, N., Nogueira, T., Cazorla, M., Gavidia-Calderón, M., Gallardo, L., Garreaud, R., Carrasco-Escaff, T., and El-Sherbany, Y. (2024). Changes in surface ozone trends in South America: exploring the effects of precursors and extreme events. Accepted in: Atmospheric Chemistry and Physics. DOI: https://doi.org/10.5194/egusphere-2024-328.

Szuba, S., Naik, V., Adhikari, P., Artaxo, P., Berntsen, T., Collins, W. D., Fawzi, S., Gallardo, L., Kindler-Schar, A., Clement, Z., Liao, H., Unger, N., and Zanis, B. (2021). Short-lived climate forces. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 817-922, doi:10.1080/j.1080-1080-108010.1017/9781009157896.008.

Tarasick, D., Galbally, I.E., Cooper, OR, Schultz, M.G., Ancellet, G., Leblanc, T., Wallington, T.J., Ziemke, J., Liu, X., Steinbacher, M., Staehelin, J. , Vigouroux, C., Hannigan, J.W., García, O., Foret, G., Zanis, P., Weatherhead, E., Petropavlovskikh, I., Worden, H., Osman, M., Liu, J., Zhang, K. L., Gaudel, A., Lin, M., Granados-Muñoz, M., Thompson, A. M., Oltmans, S. J., Cuesta, J., Dufour, G., Thouret, V., Hassler, B., Trickl. , T., and Niu, J. L. (2019). Tropospheric Ozone Assessment Report: Tropospheric ozone from 1877 to 2016, observed levels, trends and uncertainties. Science Anthology, 7, 39. https://doi.org/10.1525/elementa.376.

Degrees

[1] Current working groups: Focus Working Group on Chemical Reanalysis, Focus Working Group on East Asia, Focus Working Group on Global and Regional Models, Focus Working Group on HEGIFTOM, Focus Working Group on Ozone Impacts on Human Health, Machine Learning for Tropospheric Ozone, Focus Working Group on Ozone Deposition, Focus Working Group on Oceanic Ozone, Focus Working Group on Tropical Ozone and Precursors, Focus Working Group on Radiative Forcing, Focus Working Group on ROSTEES, Focus Working Group on Satellite Ozone, Focus Working Group on South Asia, Focus Working Group on Statistics, Tropospheric Ozone Precursors (TOP), Focus Working Group on Urban Ozone.

[2] It appears in the mole fraction of ozone in the air.

[3] Assessments (estimates) on: health, vegetation, climate, South America, Africa, stratosphere-troposphere exchange, satellite observations