Temperature vs stratospheric ozone levels

Is there a correlation between ozone levels and surface temperature?

I downloaded the stratospheric ozone level figures from here (for Southern Hemisphere, but those are the only detailed ones I could find) and the Central England Temperature Record figures from here (I know that England is not in the Southern Hemisphere, but their figures are reliable).

Annual averages jump about, so I used the five-year rolling average for temperatures.

The co-efficient of correlation for a year's five-year average and the same year's ozone levels is 60%. It increases steadily to 80% if you assume that the temperature lag is one, two, three... eight years (and falls off again after that - it's down to 50% if you assume twelve years, 37% if you assume thirteen years), which conveniently suggests that ozone levels are the cause and temperature is the effect, so I went with an eight-year lag.

The left hand axis for ozone levels is inverted, as we expect lower ozone levels to cause higher temperatures.

Here's the chart. Looks fairly convincing to me. There is a clear mismatch from 2011 to 2016, but it's all back in line from 2017 onwards. If there is a link - and I cheerfully admit that this might all be sheer coincidence - then we'd expect to see average temperatures to fall slightly over the next five years*. Not sure what happens after that:
* The average temperature for May 2020 to 2021 is slightly lower than that for May 2015 - April 2016, so the 2021 5-year average will drop towards the number 'predicted' by 2013's ozone levels.

RE: ozone depletion - how does the extra Ultraviolet B radiation affect clouds?

That's a question to which I have found no obvious answer, but I assume that if there is a bit of extra high intensity UV-B hitting the atmosphere, it will evaporate some of the clouds, i.e. turn water droplets back into water vapour. The wavelength of UV-B is orders of magnitude less than that of infra red, so the chances of it being absorbed by a molecule in a tiny water droplet is commensurately higher. And 'absorbed' just means that radiation energy is converted to some other form of energy.

This can lead to a disproportionate effect on surface and atmospheric temperatures. This theory might be totally wrong of course but it seems plausible to me. The effect must be warming, however slight. I've not put numbers on the effect because you have to make far too many assumptions so that would 'prove' nothing. This is a wait and see operation. If I live long enough to see the 'ozone hole' repair itself (perhaps by the middle of this century?) and temperatures fall again even though CO2 levels have increased (and they will), then that would support the theory but not really 'prove' it either way:

1. Starting position pre-ozone depletion

Some sunlight hits the surface, most of it hits clouds and is partially reflected: 2. There is now more UV-B (imaginatively coloured violet, even though it is invisible)

Some hits the surface; most of it hits clouds: 3. Cloud cover is reduced

Some of the energy in UV-B evaporates water droplets and so is converted to latent heat of evaporation (no measurable temperature increase). That thins the clouds slightly and reduces the amount of cloud cover. This allows more sunlight at all other wavelengths through to the surface.

So it's not so much the bit of extra UV-B which warms the surface; it is all the other sunlight that isn't reflected and that now gets through. An average reduction in cloud cover of 2% reduces albedo and increases the amount of sunlight getting through by about 1%, sufficient to cause about 1 degree of surface warming: 4. At night, the water vapour condenses into clouds again

The energy converted to latent heat of evaporation during the day turns back into extra thermal energy when the water vapour condenses again (or the rate of cooling is lower than it otherwise would be). This warms the atmosphere slightly. The surface is also slightly warmer. The pink arrows denote the extra infra red and warmth generally:

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.

Another little mystery solved...

The Alarmists tie themselves in knots trying to explain why more CO2 = cooler stratosphere. I've tried understanding the explanation in that post. It's all highly circular and it's impossible to say whether it's correct or incorrect. Here's the chart from that post. Let's take it at face value (those are The Rules):
To cut a long story short, a pressure of 200 hPa is approx. equal to the height of the troposphere, the bit we are interested in. Below that it has warmed a bit (mainly pale green) and above that (the stratosphere) it has cooled a lot (mainly dark blue).

The ever reliable (as in 'reliably wrong') Skeptical Science explains Stratospheric Cooling and Tropospheric Warming by saying that CO2 'traps' low-energy infra red radiation emitted by the Earth's surface/oceans/clouds. The stratosphere is warmed by radiation emitted from below by the troposphere. If more infrared is 'trapped' in the troposphere, it can't warm the stratosphere.
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This of course contradicts the sophisticated 'top of troposphere' theory of Global Warming (from Science of Doom, skip down to sections 5 and 6). The TOT theory says that radiation emitted by and hence temperature at the top of the troposphere (the tropopause) are a constant. More CO2 pushes up the altitude of the tropopause.

This means that surface temperature goes up because surface temperature EQUALS temperature at the tropopause PLUS the gravity-induced lapse rate (it is nice to see an Alarmist accept that this exists and has nothing to do with Greenhouse Gases) MULTIPLIED BY the altitude of the tropopause. If that is true (I like to use their own arguments against them), then the amount of infrared reaching - and warming - the stratosphere from below is unchanged!
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So far, so bad. What is the more likely explanation?

The ozone depletion theory starts on the basis that ozone in the stratosphere converts high-energy solar ultraviolet radiation from above to thermal energy. This effect appears to be undisputed. (Even the hard core Alarmists at Science of Doom accept this, while simultaneously claiming that the stratosphere is warmed from below).

When ozone is depleted in the stratosphere (mainly because of CFC gases, which break down into Cl and Br gas, which in turn act as catalysts to break down O3 into O2; partly because of volcanic eruptions) it soaks up less of the ultraviolet energy and so doesn't warm up so much, and more ultraviolet energy gets down into the troposphere and heats up the ozone (and oxygen) there instead.

Game, set and match to the ozone depletion theory, methinks! A back of the envelope approximation says that a 4% fall in stratospheric ozone levels will increase tropospheric temperatures by about 1 degree, with a larger fall in stratospheric temperatures. This matches real life results since the 1970s and ties in with the above chart.

"Global Warming is Caused by Ozone Depletion, Not Greenhouse Gases"

At last, a theory that stacks up!

See ozonedepletiontheory.info by Peter Ward for detailed explanations (and also very conscientious debunking of CO2-related theories as a bonus).

A lot of it is beyond my understanding, but on the whole it seems internally and externally consistent - temperature increases match CFC emissions much better than they match CO2 levels (that was the only thing that bothered me. Shouldn't you compare temperature increases with ozone levels?) - and very plausible. If we have to make do without spray cans and use different coolants in our fridges etc, I'm sure we can manage.

If reading is not your thing, his summary video (one hour long!) is here: