Environmental effects of stratospheric ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2019

Abstract

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.

Fig. 1

Decadal spring-time trends in UVI for the 17 sites analysed by McKenzie and colleagues. Trends in measured UVI (blue) are compared with trends calculated for clear skies from measurements of total ozone (black), and with trends calculated from total ozone derived by a chemistry-climate model according to the “World Expected” (green) and “World Avoided” (magenta) scenarios. Sites where the time series spans 20 years or more are denoted by bold text and solid symbols. The number of years of data included in the trend analysis at each site is indicated beside the site name. Error bars indicate the 95% confidence interval of the regression model.

Fig. 2

Daily maximum UV index (UVI) measured at the South Pole in 2018 (red line) compared with the average (white line) and the range (grey shading) of daily maximum observations of the years 1991 to 2017. The UVI was calculated from spectra measured by a SUV-100 spectroradiometer located at the South Pole. Up to 2009, the instrument was part of the NSF UV monitoring network and is now a node in the NOAA Antarctic UV Monitoring Network (https://www.esrl.noaa.gov/gmd/grad/antuv/). Consistent data processing methods were applied for all years.

Fig. 3

Spectral single scattering albedo (SSA) derived from AERONET, MFRSR, and Pandora measurements (blue symbols), as well as from SKYNET retrievals (orange symbols). Horizontal lines indicate the median, boxes indicate the interquartile range (IQR), whiskers extend to the minimum and maximum values within 1.5 × IQR, and outliers are shown as circles. Figure from Mok et al., licensed under the Creative Commons Attribution 4.0 License.

Fig. 4

June and December climatology of DNA-damaging fluence rate. Adapted from Madronich et al. by permission of the Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, and the European Photochemistry Association.

Fig. 5

Moss turf and lichen encrusted rocks near Casey Station in East Antarctica. Antarctic mosses emerge from under the snow in early summer and can be exposed to high solar radiation, including UV-B radiation. When plants first emerge they are bright green and those in protected areas, such as under melt water or in small depressions, will remain green; however, plants on exposed ridges quickly accumulate sunscreen pigments to protect themselves, evident here in the red-brown colour of the exposed moss. Photo by Sharon Robinson on 18 December 2012.

Fig. 6

The updated Water Quality Analysis Simulation Program 8 (WASP8) predicts the photoreactions of contaminants (here using graphene oxide as an example) as a function of the penetration of UV radiation with depth of the water column. The model can also simulate interactions of UV radiation with contaminants such as pesticides, metals, pathogens, and industrial and household organic compounds. Figure designed by Wen-Che Hou.

Fig. 7

Feedbacks from UV irradiation and melting of permafrost. Illustration by Richard Zepp.

Fig. 8

Global monthly mean methane (CH₄) concentration (reported as a mole fraction) measured by NOAA (https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/). Data from 2019 are preliminary. Figure prepared by Ed Dlugokencky (NOAA).

Fig. 9

The formation of BrVSLS in marine environments results from the reduction of hydrogen peroxide (H₂O₂) by bromide ion (Br⁻), yielding hydrobromous acid (HOBr), which subsequently reacts with dissolved organic matter (DOM) to form CHBr₃. The former reaction is catalysed by the enzyme bromoperoxidase, which is produced by micro- and macroalgae^, (figure modified from ref. 326).