• Energy Research

As part of the green transition new technologies and chemical compounds are being introduced with lower climate impact. One example is the replacement of halogenated compounds with high global warming potentials (GWPs) using compounds with low GWPs. Halogenated olefins are a family of chemicals that has been developed as alternatives to high GWP hydrofluorocarbons (HFCs). The olefinic double bond provides a reaction site for atmospheric OH radicals, lowering the atmospheric lifetime and climate impact. There is interest in the possible production of trifluoromethane (CF3H, GWP = 14,600) (IPCC, 2021) from atmospheric photolysis of CF3CHO, an oxidation product from several hydrofluoroolefins (HFOs). In addition to reaction with OH, the double bond in HFOs is reactive towards other atmospheric oxidants, including chlorine and ozone. The production of CF3H from the ozonolysis of different commercially relevant fluorinated olefins has been reported (McGillen et al., PNAS, 120, e2312714120, 2023). If CF3H is formed in the ozonolysis of HFOs, it is plausible that it would also be formed in other halogenated olefins with a CF3CH = moiety. HCFO-1233zd (CF3CH=CHCl) is a widely used hydrochlorofluoroolefin (HCFO). We report the formation of CF3H in molar yields of (6.1 ± 0.9) % and (6.4 ± 1.0) % in the ozonolysis of E- and Z-CF3CH=CHCl, respectively. This finding is discussed in the context of the contribution of halogenated olefins to the radiative forcing of climate change.

Abstract This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) addresses the interacting effects of changes in stratospheric ozone, solar ultraviolet (UV) radiation, and climate on the environment and human health. These include new modelling studies that confirm the benefits of the Montreal Protocol in protecting the stratospheric ozone layer and its role in maintaining a stable climate, both at low and high latitudes. We also provide an update on projected levels of solar UV-radiation during the twenty-first century. Potential environmental consequences of climate intervention scenarios are also briefly discussed, illustrating the large uncertainties of, for example, Stratospheric Aerosol Injection (SAI). Modelling studies predict that, although SAI would cool the Earth’s surface, other climate factors would be affected, including stratospheric ozone depletion and precipitation patterns. The contribution to global warming of replacements for ozone-depleting substances (ODS) are assessed. With respect to the breakdown products of chemicals under the purview of the Montreal Protocol, the risks to ecosystem and human health from the formation of trifluoroacetic acid (TFA) as a degradation product of ODS replacements are currently de minimis. UV-radiation and climate change continue to have complex interactive effects on the environment due largely to human activities. UV-radiation, other weathering factors, and microbial action contribute significantly to the breakdown of plastic waste in the environment, and in affecting transport, fate, and toxicity of the plastics in terrestrial and aquatic ecosystems, and the atmosphere. Sustainability demands continue to drive industry innovations to mitigate environmental consequences of the use and disposal of plastic and plastic-containing materials. Terrestrial ecosystems in alpine and polar environments are increasingly being exposed to enhanced UV-radiation due to earlier seasonal snow and ice melt because of climate warming and extended periods of ozone depletion. Solar radiation, including UV-radiation, also contributes to the decomposition of dead plant material, which affects nutrient cycling, carbon storage, emission of greenhouse gases, and soil fertility. In aquatic ecosystems, loss of ice cover is increasing the area of polar oceans exposed to UV-radiation with possible negative effects on phytoplankton productivity. However, modelling studies of Arctic Ocean circulation suggests that phytoplankton are circulating to progressively deeper ocean layers with less UV irradiation. Human health is also modified by climate change and behaviour patterns, resulting in changes in exposure to UV-radiation with harmful or beneficial effects depending on conditions and skin type. For example, incidence of melanoma has been associated with increased air temperature, which affects time spent outdoors and thus exposure to UV-radiation. Overall, implementation of the Montreal Protocol and its Amendments has mitigated the deleterious effects of high levels of UV-radiation and global warming for both environmental and human health.

There are close links between solar UV radiation, climate change, and plastic pollution. UV-driven weathering is a key process leading to the degradation of plastics in the environment but also the formation of potentially harmful plastic fragments such as micro- and nanoplastic particles. Estimates of the environmental persistence of plastic pollution, and the formation of fragments, will need to take in account plastic dispersal around the globe, as well as projected UV radiation levels and climate change factors.

After methane, ethane is the most abundant hydrocarbon in the remote atmosphere. It is a precursor to tropospheric ozone and it influences the atmosphere's oxidative capacity through its reaction with the hydroxyl radical, ethane's primary atmospheric sink. Here we present the longest continuous record of global atmospheric ethane levels. We show that global ethane emission rates decreased from 14.3 to 11.3 teragrams per year, or by 21 per cent, from 1984 to 2010. We attribute this to decreasing fugitive emissions from ethane's fossil fuel source--most probably decreased venting and flaring of natural gas in oil fields--rather than a decline in its other major sources, biofuel use and biomass burning. Ethane's major emission sources are shared with methane, and recent studies have disagreed on whether reduced fossil fuel or microbial emissions have caused methane's atmospheric growth rate to slow. Our findings suggest that reduced fugitive fossil fuel emissions account for at least 10-21 teragrams per year (30-70 per cent) of the decrease in methane's global emissions, significantly contributing to methane's slowing atmospheric growth rate since the mid-1980s.

SummaryAll sectors of society must reduce their carbon footprint to mitigate climate change, and the healthcare community is no exception. This narrative review focuses on the environmental concerns associated with the emissions of volatile anaesthetic agents, some of which are potent greenhouse gases. This review provides an understanding of the global warming potential metric, as well as the concepts of atmospheric lifetime and radiative efficiency. The state of knowledge of the environmental impact and possible climate forcing of emitted volatile anaesthetic agents are reviewed. Additionally, the review discusses how climate metrics can guide mitigation strategies to reduce emissions and suggests present and future options for mitigating the climate impact.