A reversed trend in emissions of SF6 into the atmosphere ?

Abstract

Sulfur hexafluoride (SF6) has an extremely long atmospheric lifetime and forms the most potent greenhouse gas known. Since it further shows the potential for a substantial emission reduction of CO2-equivalents, the Kyoto protocol has placed SF6 in the focus of attention of scientists, process engineers and policy makers. Maiss and Brenninkmeijer (1998) inferred from sales data (1953–1996) and atmospheric observations (1978–1996) a chronology of the accumulation of SF6 in the atmosphere that starts at low natural background levels in the 1950s and shows a clear and distinct increase up to the year 1996. Since that time, no further sales data are available but ongoing atmospheric monitoring of SF6 reveals, that the trend of rising annual emissions seems to be broken about three years ago. From a new 8-year record of SF6 observations fromlzaíia (1991–1999) — the longest high-precision record of SF6 in the northern hemisphere — we derive annual emissions of SF6 that have declined from peak values of 6700 tons/yr in 1995 to around 4900 tons/yr in 1998. This is a reduction by 27%, equivalent to 43 million tons of CO2, and probably first of all due to the growing awareness of the climatical relevance of SF6. This has stimulated a less lavish release practice in all applications. Different scenarios of changing industrial application practices are discussed. A relationship between market price and release rate of SF6 is shown suggesting also an economical motivated emission reduction.