According to a 2007 research project, the current atmospheric theories regarding depletion of the Earth's ozone 'layer' at the poles only account for around 40% of the actual depletion as measured by NASA.
See: Is a major fraction of polar ozone loss due to a currently unknown mechanism ? (Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany)
An article covering the anomaly was published in Nature: Chemists poke holes in ozone theory , Nature 449, 382-383. Note: This topic is now deprecated - at the time of the discovery some atmospheric scientists disputed the findings.
There are also reports of large-scale emissions of undeclared (i.e. banned) ozone-destroying gases used for refrigeration, which had been overlooked.