Left: Ozone in Earth's stratosphere at an altitude of approximately 12 miles (20 kilometers) in mid-March 2011, near the peak of the 2011 Arctic ozone loss. Red colors represent high levels of ozone, while purple and grey colors (over the north polar region) represent very small ozone amounts. Right: chlorine monoxide - the primary agent of chemical ozone destruction in the cold polar lower stratosphere - for the same day and altitude. Light blue and green colors represent small amounts of chlorine monoxide, while dark blue and black colors represent very large chlorine monoxide amounts. The white line marks the area within which the chemical ozone destruction took place

As early as the 1970's scientists had been warning the world of the dangers of man-made chlorine compounds and their effects on the ozone layer but it wasn't until 1989 that the Montreal Protocol brought about international action to reduce the damage for which we had been responsible.

The ozone layer is an essential component of a life-supporting planet Earth, protecting life from potentially harmful UV radiation and its adverse effects.

The depletion of this protective barrier is mainly due to our use of halogenated ozone depleting substances such as CFCs (Chlorofluorocarbons). Despite a general reduction in CFC emissions, the damage will stay with us for a considerable time and it is suggested that we may not see a recovery of the ozone layer in the Antarctic until after 2050.

As the success of the Montreal Protocol is so important to the world, the levels are closely monitored and a recent NASA study has resulted in an alarming finding. They revealed that ozone depletion over the Arctic in 2011 was considerably higher than models predicted, more closely matching the extreme losses seen in the Antarctic.

The reason for the surprise is that normally the warmer temperatures of the Arctic reduce the production of the forms of chlorine necessary for reaction with the ozone molecules. This year saw an extended cold spell in the Arctic, giving man-made compounds a longer period when reactions with ozone were viable.

NASAs role in this study was key, and involved the use of CALIPSO and Aura. CALIPSO monitors cloud cover and other aerosols in the Earth's atmosphere, while Aura monitors the ozone layer and air quality.

The combination of data from these satellites and measurements from weather balloons and meteorological stations was the basis of this study and without these spacecraft this work may not have been possible. Gloria Manney, who led the study, commented that without this capability our ability to analyse and predict the effects of ozone loss will be significantly diminished.

Recent announcements from the American government reveal that NASA faces huge funding cuts and there is the possibility that research programmes, such as these, could be put at risk. Let's hope that financial difficulties don't put this important project to bed.