« Previous | Contents | Next »
Listen
global atmosphere
Column Ozone Measurements: 1981-2005
Column ozone concentrations (Dobson units)
Station | 1981 | 1985 | 1990 | 1995 | 2000 | 2003 | 2004 | 2005 |
|---|
Lerwick | 358.7 | 334.8 | 337.2 | 328.2 | 328.4 | 338.5 | 329.5 | 320.2 |
|---|
The stratospheric ozone layer, located around 10-30km above the Earth's surface, forms a protective shield against harmful solar ( UVB) radiation. 15 Thinning of the ozone layer has occurred since the beginning of the 1980s in all regions except equatorial ones. Depletion is most marked in the Antarctic where, in 2004, the Antarctic ozone hole reached 24 million square kilometres in area (just over 300 times the land area of Scotland). 14 Ozone depleting substances ( ODS) include chlorofluorocarbons ( CFCs), hydrochlorofluorocarbons and halons, which are used as refrigerants, solvents, foam blowing agents and aerosol propellants.
The 1987 Montreal Protocol set guidelines to eliminate the global production and use of ODS. European production of CFCs for non-essential use fell to zero in 1995. 14 However, leaks from old equipment and the long life of these substances in the lower atmosphere mean that full recovery of the ozone layer is not predicted until 2050.
Over the last 25 years, the annual average total ozone cover over Lerwick has shown the natural interannual variability which would be expected due to varying meteorological conditions, but generally levels have decreased over this period. Record levels of chemical ozone depletion were reported at Lerwick in March 2005. This has been attributed to local meteorological conditions and the passage of Arctic lower stratospheric air in which ozone has been depleted.
SOURCE: MET. OFFICE, NETCEN
« Previous | Contents | Next »