Can the Ozone Hole Be Fixed?
Summer at the South Pole; Credit: Galileo Project, NASA.
JB: This is Earth and Sky. We recorded this question at the Austin Children’s Museum in Texas from Kayla Welch.
Kayla Welch: Can the hole in the ozone layer be fixed?
DB: Kayla, scientists have measured an ozone hole over the South Pole every year since the early 1980s. The hole is caused by powerful chemicals, called CFCs. Eric Betterton is a professor of atmospheric science at University of Arizona. He says that last year’s ozone hole was the worst on record.
JB: He points out that the hole isn’t always there. It appears over Antarctica in September or October each year – then disappears by mid-December as winds bring in fresh ozone and carry away the CFCs responsible for ozone depletion. But can the ozone hole be fixed permanently? Many nations have now banned CFCs. All else being equal, the ozone hole is expected to be completely fixed in about 50 to 100 years.
DB: Rob Jackson is a biologist at Duke University. He reminded us that ozone-attacking chemicals must remain banned. He also notes that most CFC substitutes are powerful greenhouse gases. They contribute to global warming.
JB: And all the scientists we talked with agreed that fixing global warming will be far trickier than fixing the ozone hole. Today’s show was made possible by the National Oceanic and Atmospheric Administration and by the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
Links:
The Science of Ozone Depletion (Environmental Protection Agency)
Authors Notes:
The ozone story is largely a success because the Montreal Protocol banned CFCs. Developed countries no longer produce CFCs and a handful of developing countries do so, but its production will eventually be phased out completely. John Harte and Rob Jackson agree that the success of the ozone story comes largely because CFCs were quite easy to replace industry was able to find straightforward chemical substitutes for CFCs. Both scientists also agree that the ozone story would make a wonderful template for fixing climate change. But, they say, a climate change “fix” is far, far trickier. Greenhouse gases are pervasive. Everyone creates carbon dioxide because our economy is based almost entirely on fossil fuel use. It will be difficult to find and implement substitutes for these fossil fuels since our whole lifestyle is based on them, says Jackson. But, he emphasizes, the ozone story is very important because it reminds us that something can be done. And that we should remember the cautionary principle: the problems we are creating now in relation to climate change will take decades-centuries-or more to go away, even if we stop all greenhouse gas production now. To illustrate the difficulties of change, Jackson adds that the United States continues to use methyl bromide, another potent ozone destroyer, because no successful substitutes have been found. This chemical is used as a fumigant in agriculture. Eric Betterton agrees that the reason scientists now expect the ozone hole to disappear is the success of the Montreal Protocol and the banning of CFCs. Betterton adds a few points of interest:
1. October 2003 was the worst year on record in terms of the amount of ozone covering the South Pole. But, he points out, scientists expect the hole to get worse and worse until it gets better. That’s because CFCs and other ozone-destroying chemicals remain in the atmosphere even though they have been largely banned. Until these break down and dissipate, we expect them to continue degrading the atmospheric ozone over the South Pole.
1. The ozone hole only forms over Antarctica, not the Arctic. That’s due almost entirely to the different weather conditions. Here’s why: In Antarctica, the weather gets SO COLD, due to its isolation from other land masses and its location in the center of a polar ocean, that air temperatures in winter regularly reach ?80 C. That kind of cold, and the seasonal formation of atmospheric vortex over Antarctica, allows the formation of so-called polar stratospheric clouds (PSCs) which contain solid ice crystals and nitric acid. These two ingredients help catalyze the reaction between ozone and the ozone destroying chemicals like chlorine. The wind and land patterns of the Northern Hemisphere surrounding the Arctic simply do not allow the formation of PSCs.
1. A potential complication: There is a possible link between ozone depletion and climate change. As climate warms, scientists predict that there will be global cooling in the stratosphere. If that should happen, there is a chance that the Arctic may see the formation of PSCs. If that happens, then it?s possible another ozone hole could form over the Arctic, in the Northern Hemisphere.
Additional points: Chlorine in the form seen in stratospheric ozone is not known in nature. So scientists quickly realized that human activity had caused it. Climate change could change the timing of when we can expect the ozone hole to disappear. And since the substitutes for CFCs are potent greenhouse gases themselves, this is a possibility.The following people were interviewed for today’s program. Our thanks to:
Dr. Eric A. Betterton
Professor of Atmospheric Sciences
Professor of Chemical and Environmental Engineering Department of Atmospheric Sciences
The University of Arizona
Tucson, AZ
Dr. John Harte
Professor Energy and Resources Group
University of California
Berkeley, CA
Robert B. Jackson
Department of Biology and Nicholas School of the Environment and Earth Sciences
Duke University
Durham, NC
