|Image Credit: Markos Possel Mapos|
A few weeks ago word spread of the passing of F. Sherwood Rowland. The first notice was a press release on the UC Irvine website. He had an illustrious career as a chemist and won a Nobel Prize in Chemistry. I never had the pleasure of meeting him, but there are few in meteorology that didn’t know of him. Those who knew him can tell you more about his career and they can be found at Real Climate and Climate Progress. Rowland was a member of the National Academy of Sciences where there is a wonderful tribute to him.
Rowland along with post-doctoral student Mario Molino found that chlorofluorocarbons (CFCs), a man-made substance, could be highly destructive to ozone. One CFC could destroy up to 100,000 ozone molecules. This could be damaging to the ozone layer even at concentration on the order of parts per billion. The discovery led to their landmark paper published in Nature in 1974.
There were no observations at the time to confirm this, but it would not take long. The first sign of trouble was reported by British scientists making measurements in the Antarctic. Very low readings were being reported, but NASA could not confirm the observations from its satellite record. A software glitch was found to be preventing NASA from seeing the low readings. It turns out that the software was simply ignoring readings below 180 Dobson units, a measure of ozone concentration.
NASA was then able to confirm the British observations once the glitch was corrected and the data re-examined. What they found was a tremendous hole in the ozone layer over the southern polar region. The discovery sent shock waves through the scientific community and an international effort to study the phenomena was organized.
The scientific team included Susan Solomon, an atmospheric chemist, who proposed that CFCs combined with an extremely cold stratosphere were in fact destroying the ozone layer. It wasn’t that the ozone was all gone, just severely depleted. This heightened concerns and an effort to stop CFC production led to the Montreal Protocol in 1987. The ozone continued to decline even though CFC production came to a halt in 2000.
This led to the Nobel Prize for Rowland and his colleagues in 1995. It was an example of discovery in the laboratory applied to the real world. When the danger was recognized action saved the day.
The story above is a much simplified version of reality and reality is never simple or nice. Sherry Rowland endured much criticism for his findings often from those who either knew nothing about atmospheric chemistry or who belonged to the industry producing the chemical.
I hear some of these myths even today and this is where I became familiar with his work. One of the most frequent myths is that CFCs are too heavy to exist high in the atmosphere. Yes, CFC molecules are heavier than oxygen or nitrogen molecules. However, the atmosphere is not stratified by molecular weight. It is well mixed due to convection in the troposphere and any chemical released at the surface can make it high into the atmosphere. Molecules are no match for air currents. Much heavier substances like dust can make it into the stratosphere.
There are still a few scientists today that deny that CFCs cause ozone depletion. However, they have never substantiated their claim in peer-reviewed journals and are not taken seriously by scientists “in the know”.
The ninth lowest measurement for ozone over the Antarctic was observed in 2011. There was also an ozone hole observed over the Arctic region for the first time.
|Antarctic ozone hole in 2011. Image Credit: NASA|
|The Arctic ozone hole in 2011. Note the comparison with 2010, both taken on March 19. Image Credit: NASA|
I hear some of these same arguments today relating to carbon dioxide and climate change. The argument goes that CO2 is too heavy to be the cause on global warming in the troposphere. Again, the facts above dispel this myth. Or how about the recent statement that CO2 is not well mixed and cannot be the cause of global warming. There may temporary local concentrations of molecules especially near point sources. However, the atmosphere is well mixed through the troposphere. In fact, the concentrations are homogeneous up to the ozone layer.
Sherry Rowland had begun to study the effects of increasing greenhouse gases in recent decades. The news release from the National Academy of Sciences mentioned this. They went on to write:
Speaking to a 1997 White House roundtable on climate change, Rowland asked: "Is it enough for a scientist simply to publish a paper? Isn't it the responsibility of scientists, if you believe that you have found something that can affect the environment, isn't it your responsibility to actually do something about it, enough so that action actually takes place? …If not us, who? If not now, when?"
In 2008 he sat down with Andrew Revkin of Dot Earth and made to following comments:
During a break, I asked Dr. Rowland two quick questions. The first: Given the nature of the climate and energy challenges, what is his best guess for the peak concentration of carbon dioxide?
(Keep in mind that various experts and groups have said risks of centuries of ecological and economic disruption rise with every step toward and beyond 450 parts per million, with some scientists, most notably James Hansen of NASA, saying the long-term goal should be returning the atmospheric concentration to 350 parts per million, a level passed in 1988.)
His answer? “1,000 parts per million,” he said.
My second question was, what will that look like?
“I have no idea,” Dr. Rowland said. He was not smiling.
Joe Romm of Climate Progress has an idea. He points out that “readers of Climate Progress have an idea, since I have done my best to describe this grim future that scientists rarely model because they can’t believe humanity would be so self-destructive as to let it happen:
At 800 to 1000 ppm, the world faces multiple miseries, including:
- Sea level rise of 80 feet to 250 feet at a rate of 6 inches a decade (or more).
- Desertification of one third the planet and drought over half the planet, plus the loss of all inland glaciers.
- More than 70% of all species going extinct, plus extreme ocean acidification.”
F. Sherwood Rowland spent much of his career studying the chemistry of the atmosphere and raising the alarm about what the science said. Much like James Hansen and the multitude of climate scientists today trying to warn the world that the path we are on is unsustainable and destructive. Some call them alarmists, but their concern is backed up by the facts and the science. They are not only scientists, but also heroes.