Question: What causes the depletion of the ozone layer?
About the article "Global warming", section "Solar activity".

Candidate passages:
The stratospheric ozone layer protectively filters ultraviolet radiation (UV) from the Sun, which would otherwise damage biological systems.
The actions taken after the Montreal Protocol appeared to be keeping the planet within a safe boundary.
However in 2011, according to a paper published in "Nature", the boundary was unexpectedly pushed in the Arctic; "... the fraction of the Arctic vortex in March with total ozone less than 275 Dobson units (DU) is typically near zero, but reached nearly 45%".
The Nobel laureate in chemistry, Mario Molina, says "five per cent is a reasonable limit for acceptable ozone depletion, but it doesn't represent a tipping point".
The physicist David Fahey says that as a result of the Montreal Protocol "stratospheric ozone depletion will largely reverse by 2100.
The gain has relied, in part, on intermediate substitutes, notably hydrochlorofluorocarbons (HCFCs), and the growing use of compounds that cause no depletion, such as hydrofluorocarbons (HFCs).
Ongoing success depends on several steps:  "Continue observing the ozone layer to promptly reveal unexpected changes.
Ensure that nations adhere to regulations; for example, the HCFC phaseout will not be complete until 2030.
"Maintain the Scientific Assessment Panel under the protocol.
It attributes causes of changes in the ozone layer and evaluates new chemicals for their potential to destroy ozone and contribute to climate change.
"Maintain the Technology and Economic Assessment Panel.
It provides information on technologies and substitute compounds that helps nations assess how the demand for applications such as refrigeration, air-conditioning and foam insulation can be met while protecting the ozone layer.
"The two panels will also have to evaluate climate change and ozone recovery together.
Climate change affects ozone abundance by altering the chemical composition and dynamics of the stratosphere, and compounds such as HCFCs and HFCs are greenhouse gases.
For example, the large projected demand for HFCs could significantly contribute to climate change."
While the effect of the Antarctic ozone hole in decreasing the global ozone is relatively small, estimated at about 5% per decade, the hole has generated a great deal of interest because:  The decrease in the ozone layer was predicted in the early 1980s to be roughly 7% over a 60-year period.
The sudden recognition in 1985 that there was a substantial "hole" was widely reported in the press.
The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error.
Many of those unsure about what the ozone hole was and what caused it were worried that ozone holes might start appearing over other areas of the globe, but to date the only other large-scale depletion is a smaller ozone "dimple" observed during the Arctic spring over the North Pole.
Ozone at middle latitudes has declined, but by a much smaller extent (about 4–5% decrease).
If the conditions become more severe (cooler stratospheric temperatures, more stratospheric clouds, more active chlorine), global ozone may decrease at a much greater pace.
Standard global warming theory predicts that the stratosphere will cool.
When the Antarctic ozone hole breaks up, the ozone-depleted air drifts out into nearby areas.
Decreases in the ozone level of up to 10% have been reported in New Zealand in the month following the breakup of the Antarctic ozone hole, with ultraviolet-B radiation intensities increasing by more than 15% since the 1970s.  
The Scientific Assessment of Ozone Depletion is a sequence of reports sponsored by WMO/UNEP.
The most recent is the 2010 report.
The reports were set up to inform the Montreal Protocol and amendments about ozone depletion.  
Since the ozone layer absorbs UVB ultraviolet light from the sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increase in skin cancer.
This was the reason for the Montreal Protocol.
Although decreases in stratospheric ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead to increases in surface UVB, there is no direct observational evidence linking ozone depletion to higher incidence of skin cancer and eye damage in human beings.
This is partly because UVA, which has also been implicated in some forms of skin cancer, is not absorbed by ozone, and it is nearly impossible to control statistics for lifestyle changes in the populace. 
There is a common misconception that the "ozone hole" is really a hole in the ozone layer.
When the "ozone hole" occurs, the ozone in the lower stratosphere is destroyed.
The upper stratosphere is less affected, so that the amount of ozone over the continent decreases by 50 percent or even more.
The ozone does not disappear through the layer, nor is there a uniform 'thinning' of the ozone layer.
The "hole" is a "depression", not in the sense of "a hole in the windshield".