Posts Tagged ‘ozone depletion’

“Global warming…doesn’t that have something to do with the ozone?” Well, no. Environmental issues are not all the same. It’s common for people to confuse climate change and ozone depletion, but they are separate issues – although they are indirectly connected in some interesting ways.

Ozone, which is made of three oxygen atoms stuck together (instead of two, which is what normal oxygen gas is made of), is vital to life on Earth. It forms a layer in the stratosphere, the second layer up in the atmosphere, that is very good at absorbing ultraviolet (UV) radiation from the Sun. UV radiation severely damages organisms if enough of it reaches the surface. The 3% or less that gets through the ozone already gives us sunburns and skin cancer, so you can imagine what the situation would be like if the ozone layer wasn’t there at all.

In the middle of the 20th century, synthetic gases known as chlorofluorocarbons (CFCs) became popular for use in refrigerators and aerosol products, among other applications. They were non-toxic, and did not react easily with other substances, so they were used widely. However, their chemical stability allowed them to last long enough to drift into the stratosphere after they were emitted.

Once in the stratosphere, the CFCs were exposed to UV radiation, which was able to break them down. Free chlorine atoms (Cl) were liberated, a substance that is very reactive indeed. In fact, Cl acts as a catalyst in the decomposition of ozone, allowing two ozone molecules to become three oxygen molecules, losing their UV absorbing power in the process. Since catalysts are not used up in a reaction, the same Cl radical can continue to destroy ozone until it reacts with something else in the atmosphere and is removed.

Over the poles, the stratosphere is cold enough for polar stratospheric clouds (PSCs) to form. These PSCs provided optimum conditions for the most reactive chlorine gas of all to form: ClO (chlorine monoxide). Now there wasn’t just a catalytic cycle of free Cl radicals depleting the ozone, there was also a cycle of ClO. It turns out that Antarctica was more favourable for ozone depletion than the Arctic, both because its temperatures were lower and because its system of wind currents prevented the ozone-depleting substances from drifting out of the area.

Before long, there was a hole in the ozone layer over Antarctica (due to the PSCs), and concentrations were declining in other locations too (due to the basic Cl reactions). The issue became a frontier for scientific research, and scientists Crutzen, Rowland, and Molina won the 1995 Nobel Prize in Chemistry for their work with atmospheric ozone.

In 1987, politicians worldwide decided to ban CFCs under the Montreal Protocol. This movement was largely successful, and the use of CFCs has become nearly negligible, especially in developed nations. They have been replaced with gases that safely decompose before they reach the stratosphere, so they don’t interfere with ozone. The regulations are working: the ozone hole in Antarctica has stabilized, and global stratospheric ozone concentrations have been on the rise since 1993.

In contrast, climate change is a product of greenhouse gases such as carbon dioxide. Unlike CFCs, most of them are not synthetic, and they are released from the burning of fossil fuels (coal, oil, and natural gas), not specific products such as refrigerators. Rather than destroying a natural process, like CFCs do, they strengthen one to the point of harm: the greenhouse effect. This phenomenon, which traps heat in the atmosphere, is absolutely vital, as the Earth would be too cold to support life without it. Increasing the concentrations of greenhouse gases with fossil fuels becomes too much of a good thing, though, as the greenhouse effect traps more heat, warming the planet up.

Just a few degrees Celsius of warming can cause major problems, as agricultural zones, wind and ocean currents, and precipitation patterns shift. The sea level rises, submerging coastal cities. Many species go extinct, as the climate changes faster than they can adapt. Basically, the definition of “normal” in which our civilization has developed and thrived is changing, and we can’t count on that stability any more.

Unlike the Montreal Protocol, efforts to reduce greenhouse gas emissions have more or less failed. Fossil fuels permeate every part of our lives, and until we shift the economy to run on clean energy instead, convincing governments to commit to reductions will be difficult at best. It remains to be seen whether or not we can successfully address this problem, like we did with ozone depletion.

Although these two issues are separate, they have some interesting connections. For example, PSCs form in cold areas of the stratosphere. That’s why the ozone hole is over Antarctica, and not somewhere else. Unfortunately, global warming is, paradoxically, cooling the stratosphere, as a stronger greenhouse effect means that less heat reaches the stratosphere. Therefore, as climate change progresses, it will make it easier for the ozone depletion reactions to occur, even though there are fewer CFCs.

Additionally, CFCs are very strong greenhouse gases, but their use has drastically reduced so their radiative effects are of lesser concern to us. However, some of their replacements, HFCs, are greenhouse gases of similar strength. They don’t deplete the ozone, but, per molecule, they can be thousands of times stronger than carbon dioxide at trapping heat. Currently, their atmospheric concentrations are low enough that they contribute far less forcing than carbon dioxide, but it wouldn’t take a large increase in HFCs to put us in a bad situation, simply because they are so potent.

Finally, these two issues are similar in that ozone depletion provides a smaller-scale analogue for the kinds of political and economic changes we will have to make to address climate change:

  1. Unintended chemical side effects of our economy posed a serious threat to all species, including our own.
  2. Industry representatives and free-market fundamentalists fought tooth and nail against conclusive scientific findings, and the public became bewildered in a sea of misinformation.
  3. Governments worked together to find sensible alternatives and more or less solved the problem.

We’ve already seen the first two events happen with climate change. Will we see the third as well?


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I waited a long time to read this book – in retrospect, too long. I have long been a fan of Naomi Oreskes; I believe she is a brilliant and sensible scientist with a compelling way with words. On the other hand, nothing depresses me more quickly than reading about those who deliberately spread confusion on climate change for political reasons. After a particularly battering year for climate science in the public eye, I want to make sure I stay sane.

However, Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming, by Naomi Oreskes and Erik Conway, was oddly comforting. How could it be so, you might ask, given the subject matter?

It’s a good question. The book traces several key players, such as Frederick Seitz, S. Fred Singer, Bill Nierenberg, and Robert Jastrow, in their fight against mainstream science. Many of them were physicists in the era of atomic bomb development, and nearly all had been deeply influenced by the Cold War – they were anti-Communist to the point of extremism.

This extremism soon extended into science: any new discovery that seemed to necessitate government action was vehemently attacked by Seitz et al. Whether it was the harmful health effects of smoking, second-hand smoking, or DDT, and the existence of anthropogenic acid rain, ozone depletion, or climate change, the same people used the same strategies to sow doubt in the public mind, delaying the cry for action. The algorithm was relatively simple:

  • construct arguments against the phenomenon, which scientists had already addressed and ruled out
  • widely publish these arguments in the popular press, rather than scientific journals
  • demand that the mainstream media be neutral and provide “equal time” for their side of the so-called controversy
  • attack the professional integrity of the scientists who discovered and studied the phenomenon; label them as frauds and/or Communists
  • claim that action on this issue would be the beginning of the “slippery slope to socialism”

It’s enough to anger anyone who has the least bit of sympathy for science. The authors say it best:

Why would scientists dedicated to uncovering the truth about the natural world deliberately misrepresent the work of their own colleagues? Why would they spread accusations with no basis? Why would they refuse to correct their arguments once they had been shown to be incorrect? And why did the press continue to quote them, year after year, even as their claims were shown, one after another, to be false?

History repeated itself many times over, within the course of just a few decades. The attack against climate science that we are currently witnessing is just a larger-scale rehash of the pro-industry, anti-Communist fight against epidemiology, environmental chemistry, and so on. Until now, few attempts have been made to connect the dots, but Oreskes and Conway present a watertight and compelling thesis in Merchants of Doubt.

The hopeful part came when I realized this: all of the previous issues that Seitz et al attempted to discredit were eventually addressed, more or less successfully, by the government, even if some of the public is still confused about the science. Restrictions and regulations on smoking, along with education regarding its harms, has made tobacco use a semi-stigmatized practice in my generation, rather than a near-universal activity. The Montreal Protocol was largely a success, and stratospheric ozone is on the rise. The world, at least so far, has managed to avoid nuclear warfare.

Climate change is undoubtedly a more inevitable and wide-ranging problem, as it strikes at the heart of our fossil-fuel based economy, and will probably surpass, both in rate and magnitude, any change our species has seen in the global environment. However, since the attack against climate science has tracked so closely with previous campaigns, I can’t help but hope it will eventually end the same way: with the public and the government realizing the problem and employing effective measures to address it. I know it’s probably not very scientific of me to make this connection, but hope doesn’t have to be rational to be effective.

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