Abstract
Abstract. We report a 40-year history of SF6 atmospheric mole fractions measured at the Advanced Global Atmospheric Gases Experiment (AGAGE) monitoring sites, combined with archived air samples, to determine emission estimates from 1978 to 2018. Previously we reported a global emission rate of 7.3±0.6 Gg yr−1 in 2008 and over the past decade emissions have continued to increase by about 24 % to 9.04±0.35 Gg yr−1 in 2018. We show that changing patterns in SF6 consumption from developed (Kyoto Protocol Annex-1) to developing countries (non-Annex-1) and the rapid global expansion of the electric power industry, mainly in Asia, have increased the demand for SF6-insulated switchgear, circuit breakers, and transformers. The large bank of SF6 sequestered in this electrical equipment provides a substantial source of emissions from maintenance, replacement, and continuous leakage. Other emissive sources of SF6 occur from the magnesium, aluminium, and electronics industries as well as more minor industrial applications. More recently, reported emissions, including those from electrical equipment and metal industries, primarily in the Annex-1 countries, have declined steadily through substitution of alternative blanketing gases and technological improvements in less emissive equipment and more efficient industrial practices. Nevertheless, there are still demands for SF6 in Annex-1 countries due to economic growth, as well as continuing emissions from older equipment and additional emissions from newly installed SF6-insulated electrical equipment, although at low emission rates. In addition, in the non-Annex-1 countries, SF6 emissions have increased due to an expansion in the growth of the electrical power, metal, and electronics industries to support their continuing development. There is an annual difference of 2.5–5 Gg yr−1 (1990–2018) between our modelled top-down emissions and the UNFCCC-reported bottom-up emissions (United Nations Framework Convention on Climate Change), which we attempt to reconcile through analysis of the potential contribution of emissions from the various industrial applications which use SF6. We also investigate regional emissions in East Asia (China, S. Korea) and western Europe and their respective contributions to the global atmospheric SF6 inventory. On an average annual basis, our estimated emissions from the whole of China are approximately 10 times greater than emissions from western Europe. In 2018, our modelled Chinese and western European emissions accounted for ∼36 % and 3.1 %, respectively, of our global SF6 emissions estimate.
Highlights
Of all the greenhouse gases regulated under the Kyoto Protocol (United Nations, 1998), SF6 is the most potent, with a global warming potential (GWP) of 23 500 over a 100-year time horizon (Myhre et al, 2013)
We show that, during the last decade (2008–2018), emissions have increased by approximately 24 % to 9.04 ± 0.35 Gg yr−1
At 2018 levels, SF6 emissions are equivalent to 212±8 Tg CO2
Summary
Of all the greenhouse gases regulated under the Kyoto Protocol (United Nations, 1998), SF6 is the most potent, with a global warming potential (GWP) of 23 500 over a 100-year time horizon (Myhre et al, 2013) In practical terms, this high GWP means that 1 t of SF6 released to the atmosphere is equivalent to the release of 23 500 t of carbon dioxide (CO2). It has been suggested that SF6 may have a shorter atmospheric lifetime of 1937 ± 432 years (Patra et al, 1997), 580–1400 years (Ray et al, 2017), or 1120–1475 years (Kovács et al, 2017) These shorter, but still very long, SF6 lifetimes would not significantly affect SF6 emissions estimated from atmospheric trends (Engel et al, 2019). Changing the lifetime from 3000 to 1000 years changed the
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