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”.
Observational Note:
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.
To learn more about the science and
what the deniers claim I encourage you to visit Skeptical Science. To learn more from actual climate scientists I
recommend Real Climate.