New threat to ozone layer

The Antarctic ozone hole is beginning to show signs of recovery, but a new threat is lurking suggests a report from the United Nations: “new” CFCs discovered in the atmosphere. Although these new CFCs have never been produced on an industrial scale, small amounts have escaped as industrial by-products and are being found in lower concentrations than classic ozone depleting substances (ODS). “The newly detected CFCs have concentrations which are 100-1000 times lower than the major CFCs in the atmosphere,” said Stefan Reimann, part of the EMPA research team who contributed to the report. “Although some of them are growing, their concentration is very far from having a noticeable impact on the ozone layer” The fact that these substances can be traced shortly after they have been released is testament to the capabilities of global measurement networks say the UN. These networks act like early warning systems, ensuring that any emission of potentially hazardous substances can be identified as early as possible. “The sum of the measured tropospheric abundances of substances controlled under the Montreal Protocol continues to decrease,” the report states. “Most of the major controlled ODSs are decreasing largely as projected.” It also states that the total ozone decline has remained relatively unchanged since 2000, and that there is a clear recent ozone increase which can be explained by comparable contributions from declining ODS abundances and upper stratospheric cooling caused by carbon dioxide increases. However, levels of hydroflurocarbons (HFCs), which replaced ozone-depleting substances, are increasing by around 7% per year. “The sum of the HFCs currently used as ODS replacements makes a small contribution of about 0.5 gigatonnes CO2 equivalent emissions per year. These emissions are currently growing at a rate of 7% per year and are projected to continue to grow,” the report states. The report suggest that is the mix of these substances remains unchanged, emissions could reach 8.8 gigatonnes CO2 equivalent emissions per year by 2050 – almost the same as peak use of CFCs in the late 1980s. Although these replacements do not harm the ozone layer, they often have a high greenhouse potential and contribute to global warming. The report suggests that they should be replaced, but questions remain about what they should be substituted with as any replacement might also accumulate in the atmosphere. “The long-lived HFCs, which are the main replacement compounds of the CFCs, could exhibit a considerable impact on climate if they are emitted unabated,” said Reimann.