March 24 – Nozone Layer

Today’s Factismal: The Vienna Convention for the Protection of the Ozone Layer was adopted in 1985; the ozone hole is expected to recover around 2115.

It is hard to love a molecule whose very name means “it stinks”. But ozone is a vital part of life on Earth. Though it is harmful when found in the lower atmosphere, due to the way it makes things oxidize even faster than normal, it is essential in the stratosphere where it gathers into a region known cleverly enough as the ozone layer. This part of the stratosphere has between two and eight parts per million of ozone. Though that may not sound like much, it is enough to reduce the UV that reaches the ground by a factor of 350 million. If the UV at the top of the atmosphere were represented by the US population, then only one person would make it past the ozone layer to reach the ground.

Ozone concentration in the atmosphere; the red line shows the "hole" near the South Pole (Image courtesy NOAA)

Ozone concentration in the atmosphere; the red line shows the “hole” near the South Pole (Image courtesy NOAA)

But in the 1970s and 1980s, scientists discovered that there was a problem with the ozone layer. For some reason, the amount of ozone in the layer was dropping; it had reached the point where a large hole had developed in the ozone layer over the South Pole. (It happened there first because of the way that the Earth’s atmosphere circulates.) If the trend continued, then the depletion of the ozone layer was expected to reach disastrous proportions within the century. But what was causing the depletion?

It turned out that the cause was good intentions. In the 1920s and 1930s, most refrigerators used an ammonia gas cycle to cool food. Unfortunately, ammonia is poisonous even in small quantities. As a result, though the refrigerators improved life, they also made it a little more hazardous. Scientists developed a new cycle based on chlorofluorocarbon gasses (CFCs) that was both more efficient and less hazardous. What they didn’t know (because the ozone layer hadn’t been discovered yet) was that the CFCs would break down ozone into oxygen, which isn’t nearly as effective at reducing UV. So people started buying these new, safer refrigerators and found more uses for CFCs; one popular use was as the propellant for hairspray and other canned goop. That led to more CFCs being released into the atmosphere and more damage to the ozone layer. By the time that the damage was discovered, it was almost too late to fix it.

But there is a world of difference between “almost too late” and “too late”. In this case, the evidence was overwhelming enough that the international community took swift and decisive action. In 1985, twenty nations signed a treaty limiting the amount of CFCs that could be used. In 1992, the treaty was amended to ban CFCs. Substitutes were found for use in air conditioning, refrigeration, and hair spray.

Unfortunately, it takes time for CFCs to work their way out of the atmosphere. Even though we’ve stopped adding them, (or think that we have) the amount of CFCs has decreased by just 10%. Though that 10% reduction has prevented the ozone hole from getting any larger, it is only slowly getting smaller as more CFCs work their way out of the environment. It is expected that it will take another century before the ozone layer returns to normal.

This hole in the ozone layer and the subsequent treaty that fixed the problem couldn’t have happened unless scientists had been out there, measuring things. And ozone isn’t the only climate challenge that faces us. If you know a teen who would like to help measure key climate indicators such as rainfall and wind speed, then why not send them over to Tracking Climate In Your Backyard?

2 thoughts on “March 24 – Nozone Layer

  1. Pingback: June 24 – On Wings Of Eagles | Little facts about science

  2. Pingback: July 18 – Cloud Control | Little facts about science

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s