Stratospheric ozone, UV radiation, and climate interactions

Abstract

This assessment provides a comprehensive update of the effects of changes in stratospheric ozone and other factors (aerosols, surface reflectivity, solar activity, and climate) on the intensity of ultraviolet (UV) radiation at the Earth’s surface. The assessment is performed in the context of the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments. Changes in UV radiation at low- and mid-latitudes (0–60°) during the last 25 years have generally been small (e.g., typically less than 4% per decade, increasing at some sites and decreasing at others) and were mostly driven by changes in cloud cover and atmospheric aerosol content, caused partly by climate change and partly by measures to control tropospheric pollution. Without the Montreal Protocol, erythemal (sunburning) UV irradiance at northern and southern latitudes of less than 50° would have increased by 10–20% between 1996 and 2020. For southern latitudes exceeding 50°, the UV Index (UVI) would have surged by between 25% (year-round at the southern tip of South America) and more than 100% (South Pole in spring). Variability of erythemal irradiance in Antarctica was very large during the last four years. In spring 2019, erythemal UV radiation was at the minimum of the historical (1991–2018) range at the South Pole, while near record-high values were observed in spring 2020, which were up to 80% above the historical mean. In the Arctic, some of the highest erythemal irradiances on record were measured in March and April 2020. For example in March 2020, the monthly average UVI over a site in the Canadian Arctic was up to 70% higher than the historical (2005–2019) average, often exceeding this mean by three standard deviations. Under the presumption that all countries will adhere to the Montreal Protocol in the future and that atmospheric aerosol concentrations remain constant, erythemal irradiance at mid-latitudes (30–60°) is projected to decrease between 2015 and 2090 by 2–5% in the north and by 4–6% in the south due to recovering ozone. Changes projected for the tropics are ≤ 3%. However, in industrial regions that are currently affected by air pollution, UV radiation will increase as measures to reduce air pollutants will gradually restore UV radiation intensities to those of a cleaner atmosphere. Since most substances controlled by the Montreal Protocol are also greenhouse gases, the phase-out of these substances may have avoided warming by 0.5–1.0 °C over mid-latitude regions of the continents, and by more than 1.0 °C in the Arctic; however, the uncertainty of these calculations is large. We also assess the effects of changes in stratospheric ozone on climate, focusing on the poleward shift of climate zones, and discuss the role of the small Antarctic ozone hole in 2019 on the devastating “Black Summer” fires in Australia. Additional topics include the assessment of advances in measuring and modeling of UV radiation; methods for determining personal UV exposure; the effect of solar radiation management (stratospheric aerosol injections) on UV radiation relevant for plants; and possible revisions to the vitamin D action spectrum, which describes the wavelength dependence of the synthesis of previtamin D3 in human skin upon exposure to UV radiation. Graphical abstract

The response of aquatic ecosystems to the interactive effects of stratospheric ozone depletion, UV radiation, and climate change

“…[ 1 ]), exposure to solar UV-B radiation most frequently has undesirable effects, such as reduced productivity or survival, but in some cases, there are desirable results (at least for humans), such as inactivation of pathogens. Given that most of the effects are negative, the large increases in incident UV-B irradiance that have been avoided by adherence to the Montreal Protocol ( Bernhard et al [ 27 ], this issue) can be viewed as being largely beneficial to aquatic ecosystems and the services they provide, supporting progress toward the Sustainable Development Goals, especially SDG14 (Life Below Water) [ 281 ]. While the world has avoided increased UV-B radiation due to stratospheric ozone depletion, UV-B radiation in the aquatic environment is nevertheless changing due to global climate change and other anthropogenic effects such as increased environmental pollution, both in the air and water.…”

“…2 b). Deeper mixing in the Southern Ocean is linked to the strengthening of surface winds associated with the positive phase of the Southern Annular Mode (in turn an effect of ozone depletion) [ 26 ](see also Bernhard et al [ 27 ], this issue). Shallowing in some parts of the equatorial region has been attributed to higher precipitation and freshening of the surface layer [ 28 ].…”

“…Biological weighting functions (BWFs), which are related to action spectra (see Bernhard et al [ 27 ], this issue), are used to quantify wavelength effects on the direct photoinactivation of microorganisms and to better understand the role of microbial characteristics and environmental changes in their sensitivity to UV radiation [ 78 , 81 – 83 ]. BWFs are used in photobiological models to evaluate the effects of changes in location and time on the direct photoinactivation of these microorganisms in the aquatic environment [ 78 , 81 – 83 ].…”

First estimation of hourly full-coverage ground-level ozone from Fengyun-4A satellite using machine learning

“…Ozone (O 3 ), a crucial atmospheric constituent, holds paramount importance for both the Earth and human beings. Approximately 90% of ozone resides in the stratosphere, where it absorbs the solar ultraviolet (UV) radiation, thereby preventing UV damage to the Earth's ecosystems (Bernhard et al 2023). However, ground-level O 3 , located near the Earth's surface, poses a significant threat to the human health, such as asthma, cardio vascular diseases, respiratory tract infection, and more (McConnell et al 2002, Jerrett et al 2009, Liang et al 2019.…”

Vertebrates under ultraviolet radiation

“…Although the Montreal Protocol and its amendments have prevented global-scale increases in UVR at the Earth's surface over the past four decades, future changes in UVR reaching the Earth's surface have been suggested to be mostly dominated by changes in the climate (e.g. aerosols and cloud cover) rather than by changes in stratospheric ozone levels (Bernhard et al, 2023). It has been projected that in the tropics, UV radiation (primarily UV-B, 280-315 nm) will increase by 3%-8% by the end of this century, as a result of decreases in clouds and ozone levels (Bais et al, 2011).…”