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Global change influences biogeochemical cycles within and between environmental compartments ( i.e. , the cryosphere, terrestrial and aquatic ecosystems, and the atmosphere). A major effect of global change on carbon cycling is altered exposure of natural organic matter (NOM) to solar radiation, particularly solar UV radiation. In terrestrial and aquatic ecosystems, NOM is degraded by UV and visible radiation, resulting in the emission of carbon dioxide (CO 2 ) and carbon monoxide, as well as a range of products that can be more easily degraded by microbes (photofacilitation). On land, droughts and land-use change can reduce plant cover causing an increase in exposure of plant litter to solar radiation. The altered transport of soil organic matter from terrestrial to aquatic ecosystems also can enhance exposure of NOM to solar radiation. An increase in emission of CO 2 from terrestrial and aquatic ecosystems due to the effects of global warming, such as droughts and thawing of permafrost soils, fuels a positive feedback on global warming. This is also the case for greenhouse gases other than CO 2 , including methane and nitrous oxide, that are emitted from terrestrial and aquatic ecosystems. These trace gases also have indirect or direct impacts on stratospheric ozone concentrations. The interactive effects of UV radiation and climate change greatly alter the fate of synthetic and biological contaminants. Contaminants are degraded or inactivated by direct and indirect photochemical reactions. The balance between direct and indirect photodegradation or photoinactivation of contaminants is likely to change with future changes in stratospheric ozone, and with changes in runoff of coloured dissolved organic matter due to climate and land-use changes. 

Once thawed, up to 15% of the ∼1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO₂) by 2,100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO₂in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000–6,300 a BP) derived from soil lignin and tannin. Rates of CO₂production from photomineralization of permafrost DOC are twofold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO₂to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2,299 may be too low by ~14%.

 

The Environmental Effects Assessment Panel (EEAP) is one of three Panels of experts that inform the Parties to the Montreal Protocol. The EEAP focuses on the effects of UV radiation on human health, terrestrial and aquatic ecosystems, air quality, and materials, as well as on the interactive effects of UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than previously held. Because of the Montreal Protocol, there are now indications of the beginnings of a recovery of stratospheric ozone, although the time required to reach levels like those before the 1960s is still uncertain, particularly as the effects of stratospheric ozone on climate change and vice versa , are not yet fully understood. Some regions will likely receive enhanced levels of UV radiation, while other areas will likely experience a reduction in UV radiation as ozone- and climate-driven changes affect the amounts of UV radiation reaching the Earth's surface. Like the other Panels, the EEAP produces detailed Quadrennial Reports every four years; the most recent was published as a series of seven papers in 2015 ( Photochem. Photobiol. Sci. , 2015, 14 , 1–184). In the years in between, the EEAP produces less detailed and shorter Update Reports of recent and relevant scientific findings. The most recent of these was for 2016 ( Photochem. Photobiol. Sci ., 2017, 16 , 107–145). The present 2017 Update Report assesses some of the highlights and new insights about the interactive nature of the direct and indirect effects of UV radiation, atmospheric processes, and climate change. A full 2018 Quadrennial Assessment, will be made available in 2018/2019.