The Kigali Amendment introduced a new family of chemical compounds, which do not contribute to stratospheric ozone depletion but present a high global warming potential, under the watch of the Montreal Protocol in 2016. Earlier this year, a press note from the World Meteorological Organization entitled “Ozone layer recovery is on track, helping avoid global warming by 0.5°C” caught our attention because of the wrong conclusions that can be potentially drawn by laypersons due to an apparent linkage of ozone depletion and global warming problems. Public communication of the Montreal Protocol since the Kigali Amendment should be more careful than ever to avoid lessening the social perception of the threat of climate change, particularly considering that society already has a distorted representation of these problems, assuming causal relations between ozone depletion and climate change, that could lead to unfounded optimism towards the climate crisis.

Environmental problems were not among the core issues for the United Nations at its creation in 1945. In the 1970s, however, they created a crescendo of public concern as the threats posed by toxic chemicals, large-scale destruction of natural ecosystems, and the loss of species became visible and were obviously linked to human activity. Pollution, it was clear, did not stop at national borders and solutions required common effort. As part of the special issue on “The United Nations at Seventy-Five: Looking Back to Look Forward,” this essay explores how, as the only institution equipped to identify global problems and generate collective action toward their resolution, the UN became the platform for creating multilateral environmental agreements, convening global conferences, and mobilizing national and international effort through a progressively larger number of institutions at the national and international level to guide decisions and influence behavior. We have moved the environmental needle in terms of information, institutions, and awareness. Yet, many environmental problems persist, some are getting worse, and new challenges and, indeed, crises are emerging.

Polysulphone ultraviolet dosimetry badges were deployed daily during a British Services Antarctic Expedition to the Antarctic Peninsula, including a cruise period across the Drake Passage. The expedition was undertaken from 20 December 2011 to 7 March 2012. Badges were successfully analysed from 46 days of the expedition with a daily mean of 1.8 kJ m-2 erythemal daily dose (EDD) and a range of 0.3–4.3 kJ m-2 EDD. The results indicate that the ultraviolet EDD experienced was comparable to temperate, mid-latitude locations in the spring/late summer. The variability of the badge measurements was mostly consistent with observations from a local ground-based radiometer and equivalent satellite-derived products. However, such comparisons are limited by the changing location/altitude of the expedition and known biases in the satellite data. This highlights that the new dataset of exposure experienced at the Antarctic surface complements those produced by stationary ground-based instruments or satellites and, therefore, that the badge dataset brings a new element to this issue. The highest EDD values during the expedition occurred at high altitude, and the lowest EDD values occurred at low altitude and high latitude with relatively high total ozone column concentration.

Crisis has played a significant role in international environmental law since its inception. To some extent the field as a whole might be characterized as a ‘discipline of crisis’, since it functions as a counterbalance to unbridled pollution and resource depletion. On the other hand, there have been ongoing attempts to move away from a reactive focus on crisis and to conceptualize international environmental law as part of a broader societal shift toward sustainability. The dilemma that faces the discipline is that in the absence of a sense of crisis, we are unsure of how to generate the commitment that will be required to undertake fundamental changes to the status quo.

The Antarctic oscillation (AAO) has been characterized by a persistently positive trend in summer (December–January–February, DJF) during the last 50 years. Thus, the question has arisen of whether the trend is unusual. By investigating five reconstructed historical AAO time series for the past 500 years, recurrences of similar and even stronger trends have been found, indicating that the recent DJF AAO trend is not unprecedented in a historical perspective. To estimate the possible roles played by greenhouse gases or/and ozone, an analysis for DJF AAO trends during the 1969–98 period was conducted using three multiple model ensembles derived from the projects of ‘The twentieth-century climate in coupled models’ (20C3M) and ‘Pre-industrial control experiment models’ (PICTL) of the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC AR4). The results show that the ozone depletion over Antarctica and global warming may play significant roles in the strengthening trend. Combining the simulations and reconstructions we emphasize that the AAO trend related to global warming may get much stronger when enhanced by low-frequency natural variability.

With the possible exception of meteor impacts, high-energy astrophysical events such as supernovae, gamma-ray bursts (GRB) and flares are usually not taken into account for biological and evolutionary studies due to their low rates of occurrence. We show that a class of these events may occur at distances and time scales in which their biological effects are non-negligible, maybe more frequent than the impacts of large asteroids. We review the effects of four transient astrophysical sources of ionizing radiation on biospheres – stellar flares, giant flares from soft gamma repeaters (SGR), supernovae and GRB. The main damaging features of them are briefly discussed and illustrated. We point out some open problems and ongoing work.

Stratospheric ozone depletion threatens to increase exposure to ultraviolet (UV) radiation which is known to be a factor in a number of diseases. There is little doubt that cumulative exposure to UV radiation is important in the aetiology of non-melanoma skin cancers. Evidence is also strong for a link with cutaneous malignant melanoma, although here it appears to be intermittent intense exposure that is most damaging. More controversial is the view that exposure to solar radiation is a significant factor in ocular damage, particularly in the formation of cataracts. Earlier studies pointing to such an effect have been criticized and alternative aetiological hypotheses have been proposed. However, other studies do show an effect of UV exposure on cortical cataract. Concern is also growing that UV may be capable of activating viruses and have immunological effects that might exacerbate infectious disease. Very worrying is the possibility that UV exposure can activate the human immunodeficiency virus which might accelerate the onset of AIDS. Any such health effects that have been observed in human populations are the result of exposure to existing, naturally occurring levels of UV radiation. There is, therefore, great concern about the possible exacerbation of these impacts as a result of increased exposure to UV radiation associated with stratospheric ozone depletion. However, any assessment of the nature and scale of such impacts on human health has to deal with several major problems and these are the focus of this paper. There are uncertainties about recent trends in stratospheric ozone and problems in the prediction of future changes. Following on from this are the difficulties of estimating what effects these changes will have on UV flux at ground level in populated areas. Further problems arise in the prediction of changes in biologically significant doses to humans which might be affected by changes in behaviour as well as by changes in the environment. Finally, the limitations of existing epidemiological knowledge of the effects of UV exposure are a constraint on our ability to predict what the health effects of any changed UV doses might be.

The features of solar UV irradiance measured at the Italian-French Antarctic Plateau station, Concordia, during the springs of 2008 and 2009 are presented and discussed. In order to study the impact of the large springtime variations in total ozone column on the fraction of ultraviolet B (UV-B) irradiance (from c. 290–315 nm) reaching the Earth surface, irradiance datasets corresponding to fixed solar zenith angles (SZAs = 65°, 75° and 85°) are correlated to the daily ozone column provided by different instruments. For these SZAs the radiation amplification factor varied from 1.58–1.94 at 306 nm and from 0.68–0.88 at 314 nm. The ultraviolet index reached a maximum level of 8 in the summer, corresponding to the typical average summer value for mid latitude sites. The solar irradiance pertaining to the ultraviolet A (UV-A, 315–400 nm) spectral band was found to depend closely on variations of atmospheric transmittance characteristics as reported by previous studies. Model simulations of UV-B irradiance showed a good agreement with field measurements at 65° and 75° SZAs. For SZA = 85° the ozone vertical distribution significantly impacted model estimations. Sensitivity analysis performed by hypothetically varying the ozone distribution revealed some features of the ozone profiles that occurred in the period studied here.

In this paper we present a unified, quantitative synthesis of analytical and numerical calculations of the effects that could be caused on Earth by a gamma-ray burst (GRB), considering atmospheric and biological implications. The main consequences of the illumination by a GRB are grouped into four distinct classes and analysed separately, namely: direct γ flash, UV flash, O3 layer depletion and cosmic rays. The effectiveness of each of these classes is compared and distances for significant biological damage are given for each one. We find that the first three effects have the potential to cause global environmental changes and biospheric damage, even if the source is located at galactic distances or even farther afield (up to 150 kpc, where 1 parsec=3.09×1016 m, about five times the Galactic diameter of 30 kpc). Instead, cosmic rays would only be a serious threat for close sources (of the order of a few parsecs).

As a concrete application from a well-recorded event, the effects on the biosphere of an event identical to the giant flare of SGR1806-20 on 27 December 2004 have been calculated. In spite of not belonging to the so-called ‘classical’ GRBs, most of the parameters of this recent flare are quite well known and have been used as a calibration for our study. We find that a giant flare impinging on Earth is not a threat for life in all practical situations, mainly because it is not as energetic, in spite of being much more frequent than GRBs, unless the source happens to be extremely close.

The aim of this work was to investigate the effect of different fractions of UVR on two Antarctic marine bacteria (Arthrobacter UVvi and FCB-related UVps strains) and to study the relationship between the bacterial viability and the UVB dose. Ten experiments exposing strains to natural solar radiation were conducted in Potter Cove, South Shetland Islands. The effect of different UVR wavelengths on viability was analysed by using cultures in quartz bottles covered with interferential filters. Six treatments were performed: DARK, PAR (with UVR shielded off), UVA360, UVA320, UVB305 and UVB280. In all UVR treatments, strains showed significant losses of viability under high and moderate irradiance and no differences were observed between UV treatments. Under high UVB dose (15.0 kJ m−2 received in only two hours), the effect of UVB treatments was significantly higher than that observed under UVA treatments. However, UVA caused a significant reduction on bacterial viability. Survival rates were negatively correlated with integrated UVB dose, FCB-related UVps being more sensitive than Arthobacter UVvi. The similar values observed in viability when the same dose was received in different time periods suggested that DNA repair mechanisms are not much effective in these strains. The different response to the UV wavelength ranges studied here suggests that changes in the spectral composition of natural radiation could differentially affect the components of Antarctic marine bacterial communities.

We have determined the base composition (percentage of guanine-cytosine base pairs, GC%) of total DNA from Euphausia superba to be 32% ± 0.5%. This is the lowest GC% recorded for a metazoan. Low GC% DNA has high concentrations of thymine (T) residues and consequently a greater abundance of adjacent T residues [T(n) arrays]. Ultraviolet B (280–320 nm, UV-B) radiation damages DNA primarily at (T)n arrays, so we suggest that krill DNA may be more susceptible to damage from increased levels of UV-B radiation over the Southern Ocean than the DNA of other Antarctic organisms.

This review of polar marine ecosystems covers both the Arctic and Antarctic, identifying the major threats and, where possible, predicting their possible state(s) in 2025. Although the two polar regions are similar in their extreme photoperiod, low temperatures, and in being heavily influenced by snow and ice, in almost all other respects they are very different. The Arctic Ocean is a basin surrounded by continental landmasses, close to, and influenced by, large populations and industrial activities. In contrast, the Southern Ocean is contiguous with all the other great oceans and surrounds a single land mass; Antarctica is remote from major centres of population and sources of pollution. Marine environments in both polar regions have been highly disturbed by fishing activity, but, in terms of pollution, some areas remain among the most pristine in the world. There are, however, both local and global pressures. Over the 2025 time horizon, the greatest concern for the Arctic is probably the ecological implications of climate change, particularly insofar as sea ice extent and duration are likely to be affected. Such changes are not expected to be as pronounced in the Southern Ocean over this time period, and concerns are related more to direct threats from harvesting of marine living resources, and the ability to manage these fisheries sustainably. In both polar regions, the capacity of marine ecosystems to withstand the cumulative impact of a number of pressures, including climate change, pollution and overexploitation, acting synergistically is of greatest concern.