Thicker Ozone=Colder Earth?

Question

Our planet's best line of defense against the worst of the sun is the ozone layer. It is no thicker than 0.01 millimeters. It absorbs 97 to 99% of the sun's medium UV light (200-315 nanometers). It contains 10 parts per million of ozone in that layer alone.

With an absent or even thinner ozone layer, the sun's UV light would damage the planet to a greater extent, disrupting the course of evolution to the extent of barring it from ever reaching land.

But what if the ozone layer were thicker? Say, 10 parts per hundred of ozone, half a millimeter thick. Would a thicker shield cool down the global climate?

Answer 1

It's complicated

While the intuitive answer is yes, a thicker layer probably would do that, it may not last - or it may have counterproductive effects. It's probably not as simple as "yes".

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We're getting into feedback loops, systems whose outputs directly influence their inputs - which then influences their outputs in turn, and so on.

• Positive feedback loops change over time. The input makes a greater output, which makes a greater input, which makes a greater output ... and so the change builds
  • ex. the greater the population, the greater the birth rate, which will continue to increase the population, which will continue to increase the birth rate ... etc. The system changes itself over time.
• Negative feedback loops have no net change. The input changes the output, but eventually the process reverses itself
  • ex. increasing incoming sunlight will melt the ice caps, creating reflective clouds that decrease incoming sunlight, forming ice caps again ... The system negates its own changes.

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If you increased the amount of ozone, incoming UV radiation and exiting infrared radiation would be absorbed. This would increase the temperature of the stratosphere, potentially allowing even more ozone to form (?) in a positive feedback loop.

Conversely, too much ozone may block so much of the Earth's outgoing infrared radiation, potentially reflecting it downward, that global temperatures would increase.

Feedback loops are complicated.
Don't try this at home.

Answer 2

Ozone (O3) high in the atmosphere absorbs ultraviolet radiation from the sun, thereby protecting living organisms below from this dangerous radiation. The term ‘ozone hole’ refers to recent depletion of this protective layer over Earth's polar regions. People, plants, and animals living under the ozone hole are harmed by the solar radiation now reaching the Earth's surface—where it causes health problems from eye damage to skin cancer.

The ozone hole, however, is not the mechanism of global warming. Ultraviolet radiation represents less than one percent of the energy from the sun—not enough to be the cause of the excess heat from human activities. Global warming is caused primarily from putting too much carbon into the atmosphere when coal, gas, and oil are burned to generate electricity or to run our cars. These gases spread around the planet like a blanket, capturing the solar heat that would otherwise be radiated out into space. (For more detail on the basic mechanism of global warming, see carbon dioxide FAQ.)

Both of these environmental problems do, however, have a common cause—human activities that release gases into and alter the atmosphere. Ozone depletion occurs when chlorofluorocarbons (CFCs)—formerly found in aerosol spray cans and refrigerants—are released into the atmosphere. These gases, through several chemical reactions, cause the ozone molecules to break down, reducing ozone's ultraviolet (UV) radiation-absorbing capacity.

Because our atmosphere is one connected system, it is not surprising that ozone depletion and global warming are related in other ways. For example, evidence suggests that climate change may contribute to thinning of the protective ozone layer.

I quote the above from the below article:

http://www.ucsusa.org/global_warming/science_and_impacts/science/ozone-hole-and-gw-faq.html

This should help to answer your question in a very scientific manor.

Answer 3

Ozone absorbs a part of the EM spectrum. This part is high energy UV light. The current level of Ozone does a pretty good job of absorbing it all. A thicker ozone layer would absorb slightly more, and therefore the upper atmosphere would be slightly warmer, and the lower atmosphere and surface slightly cooler.

However, that is only its effect on incoming UV light. Like CO2, Ozone absorbs some infrared light radiated from the earth's surface. https://en.wikipedia.org/wiki/Ozone#Ozone_as_a_greenhouse_gas A thicker ozone layer would trap heat, increasing the greenhouse effect, warming the surface.

Both of these effects are minor. Ozone doesn't have a MAJOR effect on temperature.