Science Deniers!

From climate.gov:

The ozone hole did not cause global warming

Because the ozone layer normally blocks ultraviolet (UV) light, an ozone hole allows more UV light than usual to reach the surface. However, the additional energy added to the Earth system from the ozone hole is so small that it couldn’t be responsible for the warming trend that’s been occurring.

How small? Well, the vast majority of sunlight is the light we can see—visible light with wavelengths of 400-700 nanometers. UV light is only about 8 percent of all sunlight to begin with, and the ozone layer and oxygen (both of which absorb UV) only permit a fraction of that to reach the surface. The additional amount of UV that the Antarctic ozone hole allows to reach the surface for a month or so each year is a small fraction of an already small amount of sunlight—too small to explain global warming.

1. The term "ozone hole" is not supposed to be taken literally! CFC gases have reduced the overall amount of ozone in the stratosphere everywhere, it is just most noticeable over the Antarctic at certain times of the year (and to a lesser extent over the Arctic). These are precisely the areas which are warming fastest, we are told - which supports the ozone depletion theory. So more UV-B gets down to the troposphere.

2. All this chit chat about frequencies is a side show, UV might only be 8% of all frequencies in incoming solar radiation. But energy is proportional to frequency and UV carries fifty times as much energy as much lower frequency/longer wavelength IR. And CO2 only absorbs/re-emits about one-tenth of the IR frequencies which the ground, oceans and clouds emit.

3. Whatever the clever radiation calculations might be (way beyond me), it is easier just to look at outcomes. The combined effect of UV-C, UV-B rays, oxygen and ozone in the stratosphere is enough to keep the average temperature at about 245 K via a series of endothermic reactions (which absorb energy from UV) and endothermic reactions (when O + O2 re-combine to O3 and give off heat). These reactions are tricky but are accepted physics. Without ozone, and assuming the lapse rate in the stratosphere is 9.8K/km (very dry), the average temperature would be 125K (I assume). So the UV/ozone effect warms the stratosphere by average 120K.

4. The mass of the air in the stratosphere is about one-quarter of the mass of the air in the troposphere (estimates vary). There is no hard dividing line - long haul jets fly quite happily in the lower stratosphere (and Joseph Kittinger got to the upper stratosphere by balloon and parachuted down again). It's just that the stratosphere is warmed from above by UV (so it's warmest at the top) and the troposphere is warmed from below by the ground/oceans and there is a gravito-thermal effect (so it's warmest at the bottom). The tropopause (the dividing line between troposphere and stratosphere) is just where temperatures are at a minimum and rise again (if you go up or down from there). This is why most atmospheres don't have a 'stratosphere' - there is no oxygen/ozone there to cause this effect.

5. So if there were no ozone in our stratosphere whatsoever, the UV/ozone effect would warm up the troposphere instead, by up to 30 degrees (one-quarter of the extra 120 K from 3 above). Ozone levels have dropped by (say) 10% since the 1970s, so 10% more UV-B is getting through. 10% x 30 degrees = 3 degrees. If one-third goes into warming the troposphere (and the rest into oceans or is otherwise dissipated), that's your one degree of atmospheric warming since the 1970s. It's clearly not a straight line relationship or anywhere that simple, but it's a good starting assumption.

6. Furthermore, car exhausts indirectly cause more ozone at low levels ("bad ozone" for this and other reasons), so there is plenty of ozone down here to catch the UV-B that now gets through and give off heat (another possible explanation for the urban heat island effect).

7. Further reading from an apparently unbiased source here.