August 30, 2004

Ozone layer research balloons help gauge success of ODS reduction measures

Scientists from Environment Canada, the Canadian Space Agency, the University of Toronto, York University and the University of Waterloo were scheduled to launch one large ozone research balloon, plus a series of smaller balloons, last week from a farm field in Vanscoy, Saskatchewan. The balloon flights are part of a research program designed to monitor the effectiveness of measures to reduce ozone-depleting substances (ODS) undertaken since the Montreal Protocol, the global agreement aimed at protecting the ozone layer. This is the third such launch for the purpose of studying the ozone layer over Canada; similar launches were carried out in 1998 and 2002.

The primary balloon, which is the height of a 25-storey building, will carry an instrument package weighing over half a tonne (550 kg) nearly 40 kilometres up into the atmosphere. It will pass through most of the ozone layer in the earth's stratosphere as part of the MANTRA (Middle Atmosphere Nitrogen TRend Assessment) research project.

The two-metre-high payload on board the MANTRA ballon consists of 11 instruments, including an ozone-measuring instrument called MAESTRO (Measurements of Aerosol Extinction in the Stratospheric and Troposphere Retrieved by Occultation), which was developed in 2002 by Environment Canada. The original MAESTRO instrument was launched into space in 2003 on board a Canadian science satellite, and is now measuring the ozone layer from space.

The balloon-borne version of MAESTRO, and some of the other instruments that are part of the balloon payload, will take readings as the satellite passes which will serve to verify the accuracy of the measurements made from the satellite. Instrument packages will record the thickness of the ozone layer and measure CFCs and other ozone-depleting substances in the atmosphere. Scientists will compare these readings to measurements recorded by balloon flights over Saskatchewan over the past 20 years.

The extent of global ozone depletion is a cause of concern among scientists because it is still larger than predicted by the research that formed the scientific basis for the Montreal Protocol and its subsequent amendments.

Only about half of the observed ozone loss can be definitely attributed to known industrial chemicals. The ozone layer is sensitive to changes in temperature, and scientists suspect that climate change may be the cause of the unexplained additional depletion.

Other recent research findings indicate that the ozone layer has not yet recovered, despite considerable action taken to reduce ozone-depleting industrial chemicals. Ozone values have decreased by an average of about 6% since the late 1970s, with greater losses of about 8 to 10% in the springtime.

In Canada as well, ozone thinning is most severe over the Arctic. Unusual ozone thinning has been observed in this region in seven of the last 13 years, and is most severe in the late winter and early spring. The most significant depletions occurred during the late 1990s, with ozone losses of up to 45% in 1997.

Climatologists have observed some evidence which indicates that climate change is already affecting the Arctic at ground level, such as melting permafrost and shrinking glaciers. In recent years, Environment Canada scientists have also recorded temperature changes in the Arctic's upper atmosphere, which may be contributing to ozone depletion.

As a result of the thinning ozone layer, sunburning UV has increased by an average of about 7% over southern Canada, with levels increasing by 10 to 12% in the springtime. The ozone layer is naturally variable, and this summer, the average ozone thickness over southern Canada is only about 1%, causing an increase in sunburning UV of about 1.2%.

More information on the balloon research project is available on-line at www.msc.ec.gc.ca/research/balloon/index_e.html.

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