Fig. 1.

Interactive effects of solar radiation (UV and visible) and climate change on biogeochemical cycles. The numbers in the arrows refer to the following effects: (1) stratospheric ozone concentrations are affected by ozone depleting substances (ODSs) and control the intensity of solar UV radiation (see ref. 1). Climate change affects cloud formation and the intensity of UV radiation reaching the Earth’s surface (see ref. 1). Antarctic ozone depletion impacts local climates in the southern hemisphere via changes of the Southern Annular Mode (SAM) (see ref. 1 and 2), while Arctic amplification influences local climates in the northern hemisphere. Interactive effects of solar UV radiation and climate change affect the biogeochemical production and fate of greenhouse gases, particularly CO₂, but also methane (CH₄) and nitrous oxide (N₂O), that impact climate and stratospheric ozone. (2) Important consequences of climate change are warming of and loss of the cryosphere, increasing frequency and intensity of droughts, wildfires, storms, and heavy precipitation events in different regions of the Earth. (3) Loss of the cryosphere and increases in storms and heavy precipitation events result in the enhanced transport of natural organic matter (NOM) from land to water, where it is degraded to CO₂, carbon monoxide (CO), and other products by UV and visible radiation, and by microbes. (4) Similarly, degradation of NOM by UV and visible radiation, and by microbes occurs on soil surfaces. (5) Contaminants also undergo UV-induced degradation, either in direct or indirect photochemical reactions. Contaminants include organic contaminants, nanomaterials, microplastics, harmful algal blooms, and viruses.