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ozone hole What happened to the ozone hole we used to hear about?
The good news is that due to universal action the ozone hole is no longer a progressively worsening issue.

Ozone (O3) is an oxygen (O2) molecule combined with an oxygen atom for a brief moment. This is a chemical reaction that happens continuously when ultraviolet (UV) photons from our sun react with the otherwise stable O2 molecule. The relatively unstable O3 breaks down quickly back to O2 and the reaction repeats. If this chemical reaction does not occur, too much radiation makes it through to ground level where humans live.

The specific UV rays that are blocked by the ozone layer can cause skin cancer and cataracts in humans, as well as reproductive problems in fish, crabs, frogs and even single-celled phytoplankton. The formerly expanding ozone hole is located over the south pole. When I traveled to South Island New Zealand many years ago I was surprised at how quickly I sunburned despite being so far from the equator.

The problem was chlorofluorcarbons (CFCs) in aerosols and refrigerants formerly used in all spray cans, air conditioners, and refrigerators.

The United Nations Montreal Protocol of 1987 pact to ban CFCs was the first UN treaty to have universal ratification!

But that's not the end of the story...

The CFCs were replaced by hydrofluorocarbons (HFCs) that degrade through UV photolysis to CF4. While CF4 does not contribute to the ozone hole, it is a greenhouse gas.

"Atmospheric CF4 and its sources are of concern because of its atmospheric persistence, with an atmospheric lifetime estimated to be 50,000 years."

So the current focus is to find and substitute gases with similar properties that are short-lived in our atmosphere. Atmospheric chemistry is very complicated with many interacting multi-step reactions to consider. Fortunately climate scientists are on the project!

We can abate climate issues if appropriate action is taken promptly.

greenhouse gas emissions by sectorAtmosphere Counts!
via Steve

Without Earth's thin protective atmosphere we'd be in big trouble. Not only does it supply us with oxygen to breathe, but it also buffers the effects of our Sun and moderates ground level temperatures. Without greenhouse gasses (GHG) the average temperature on Earth would be approximately 30-degrees Fahrenheit colder. It's all about maintaining balance.

The average composition of our atmosphere is: ~78% nitrogen, ~21% oxygen, with the remaining ~1% as argon, neon, helium, methane, krypton, hydrogen, carbon dioxide, and nitrogen oxide. It's the composition of that 1% that is of concern.

Life on Earth has evolved to thrive within a very specific atmospheric composition but our hydrocarbon fueled activities are upsetting the balance. Most greenhouse gases have both natural and human-caused sources, and our unnatural contribution to atmospheric change is termed anthropogenic.

The major (variable) contributors to the greenhouse effect are: water vapor (H2O 36-76%); carbon dioxide (CO2 9-26%); methane (CH4 4-9%); and ozone (O3 3-7%). Water vapor (clouds) are a significant variable, but natural contributor to global warming. As an example when it's cloudy at night the temperature does not drop as much as it would with clear skies. Regional redistribution of water vapor is a function of climate change. Where I live in Colorado atmospheric water vapor has been increasing while other areas are getting dryer.

Earth absorbs some of the radiant energy from the sun and radiates the rest back into space. Albedo is the fraction of solar energy that is reflected from the surface of Earth back into space. The greenhouse effect blocks some of the bounce back into space increasing temperature. Factors that influence Earth's energy balance are quantified as radiative forcing. Positive radiative forcing is when more reflected heat is trapped by greenhouse gasses increasing temperature, while negative radiative forcing indicates cooling.

Unfortunately, atmospheric CO2 has recently been recorded at its highest levels since measurement began, hovering just below 400ppm. During pre-industrial times CO2 was typically much lower at ~280ppm. Carbon dioxide is the result of hydrocarbon combustion from fossil fuels. Carbon dioxide is absorbed (fixed) by plants and trees (photosynthesis), as well as oceans. Fewer trees by clear-cutting for agricultural space leads to an overabundance of CO2, and more CO2 fixed by oceans leads to acidification. Acidification creates a unfavorable PH for sensitive species like coral.

Ozone is a good thing high up to block harmful UV wavelengths, but not good at ground level.

Ozone at ground level is a known irritant to mucus membranes in our lungs and associated with many deaths, especially in those afflicted with asthma. I can recall going for long training rides on the bike during hot summer days and not being able to take a deep breath for hours after. I lived 25-miles northeast of New York City, so with prevailing winds from the west it is some of the worst air quality in the US.

Nitrogen oxides (NOx) are currently in the news as it's the problematic component of diesel combustion and a potent greenhouse gas contributor. The Volkswagon scandal is about exceeding nitrogen oxide emission standards. Another danger of NOx is that they eventually form nitric acid when dissolved in atmospheric moisture forming a component of acid rain. Acid rain can create an overly acidic condition in lakes harming fish and other fresh water creatures.

Small changes high up in the atmosphere make a big difference at ground level where we live and breathe. So far the year-round planet-wide average is up from ~55f to almost 57f. With increasing carbon dioxide and methane levels in our atmosphere temperatures will keep rising, causing change that will be tough to adapt to over the short term. Unfortunately this is the direction we're currently going. The challenge is to maintain the balance in our atmosphere at levels prior to industrialization.

The target goal is to keep the temperature rise to less than 2c (<3.6f) and so it's all about reducing our activities that burn carbon based fuels. The problem can be fixed if we're open to innovation, change, and sacrificing some old habits for new ways of thinking about the problem and appropriate action.

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