CFC ban bought us time to fight climate change

 From The BBC

A worldwide ban on ozone-depleting chemicals in 1987 has averted a climate catastrophe today, scientists say.

The Montreal Protocol on Substances that Deplete the Ozone Layer, banning chemicals such as chlorofluorocarbons, has now simulated our "world avoided".

Without the treaty, Earth and its flora would have been exposed to far more of the Sun's ultraviolet (UV) radiation.

Former UN Secretary General Kofi Annan has called it "perhaps the single most successful international agreement".

Continued and increased use of chlorofluorocarbons (CFCs) would have contributed to global air temperatures rising by an additional 2.5°C by the end of this century, the international team of scientists found.

Part of that would have been caused directly by CFCs, which are also potent greenhouse gases. [Producing CFCs on Mars has been proposed as a way of terraforming Mars and raising its surface temperature.]

But the damage they cause the ozone layer would also have released additional planet-heating carbon dioxide - currently locked up in vegetation - into the atmosphere.

"In past experiments, people have exposed plants - basically tortured plants - with high levels of UV," lead researcher Dr Paul Young, of the Lancaster Environment Centre, said.

The scientists estimated there would be:

• 580 billion tonnes less carbon stored in forests, other vegetation and soils
• an extra 165-215 parts per million (40-50%) of carbon dioxide in the atmosphere

"What we see in our 'world-avoided experiment' is an additional 2.5C warming above any warming that we would get from greenhouse-gas increases," Dr Young said.

But similar collective action to limit greenhouse-gas emissions was likely to be much more challenging.

"The science was listened to and acted upon - we have not seen that to the same degree with climate change," he told BBC Radio 4's Inside Science programme.

The experiment could appear to suggest hope for an "alternative future" that had avoided the worst consequences of climate change.

"But I would be cautious of using it as a positive example for the climate negotiations," Dr Young said.

"It's not [directly] comparable - but it's nice to have something positive to hold on to and to see that the world can come together."

The ozone hole over Antarctica, in 2000

Ozone pollution tied to cardiovascular disease

I must confess, I used not to worry too much about air pollution, I suppose because I live in a relatively unpolluted part of the world, in the countryside.  Recently, however, I've been getting chronic bronchitis, and so I started doing research on what might cause it.  One of the possibilities is air pollution.  When we moved here 8 years ago, the road outside our house was a lot less busy than it is now.  Now, in our front yard, we can smell diesel fumes.  The reality of air pollution has become personal.

Here's Wikipedia on low level (near the surface of the earth) ozone:

Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind. 

Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog. Ozone photolysis by UV light leads to production of the hydroxyl radical HO• and this plays a part in the removal of hydrocarbons from the air, but is also the first step in the creation of components of smog such as peroxyacyl nitrates, which can be powerful eye irritants. 

[Read more here]

It turns out that tropospheric ozone is a powerful greenhouse gas too, but fortunately, unlike CO2, it's relatively short-lived.

Although ozone was present at ground level before the Industrial Revolution, peak concentrations are now far higher than the pre-industrial levels, and even background concentrations well away from sources of pollution are substantially higher. Ozone acts as a greenhouse gas, absorbing some of the infrared energy emitted by the earth. 

Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe. However, the most widely accepted scientific assessments relating to climate change (e.g. the Intergovernmental Panel on Climate Change Third Assessment Report) suggest that the radiative forcing of tropospheric ozone is about 25% that of carbon dioxide. 

The annual global warming potential of tropospheric ozone is between 918–1022 tons carbon dioxide equivalent/tons tropospheric ozone. This means on a per-molecule basis, ozone in the troposphere has a radiative forcing effect roughly 1,000 times as strong as carbon dioxide. However, tropospheric ozone is a short-lived greenhouse gas, which decays in the atmosphere much more quickly than carbon dioxide. This means that over a 20-year span, the global warming potential of tropospheric ozone is much less, roughly 62 to 69 tons carbon dioxide equivalent / ton tropospheric ozone. 

Because of its short-lived nature, tropospheric ozone does not have strong global effects, but has very strong radiative forcing effects on regional scales. In fact, there are regions of the world where tropospheric ozone has a radiative forcing up to 150% of carbon dioxide.

[Read more here]

Now comes the research that ozone significantly increases the risk of cardio-vascular disease.

Ozone air pollution has now been directly tied to the risk of developing cardiovascular disease, which expands the list of health effects known to be caused by ozone exposure, and also lowers the threshold at which ozone is known to be dangerous (by a fair amount). 

To explain, it’s been known for quite some time that exposure to ozone is associated with reduced lung function — and everything that goes along with that — but the new work now shows that high blood pressure (and the risk of experiencing a heart attack and/or a stroke) are associated with it as well. 

These effects were found with ozone exposure lower than that which affects respiratory health, and lower than current Environmental Protection Agency (EPA) air quality standards.

[Read more here]

Burning fossil fuels isn't just causing global warming.  It's also causing pollution which is killing us.  More on that in my next post.