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The Keeling Curve

By: Dr. Jeff Masters, 2:46 PM GMT on June 27, 2005

Dr. Charles D. Keeling, whose pioneering work on measurement of atmospheric carbon dioxide levels helped draw attention to the global warming issue, died June 20, 2005, at his home in Montana. He was 77. The cause was a heart attack after a short hike, acording to the Scripps Institution of Oceanography in San Diego, where Dr. Keeling had long worked.

In 1955, Keeling became the first researcher to take measurements of atmospheric CO2 and establish that levels were the same regardless of the location. Mountaintops or polluted cities, California or Hawaii, it didn't matter--the magic number 315 parts per million (ppm) invariably came up. Keeling did note a seasonal fluctuation--CO2 values increased steadily during the winter, peaking at about 318 ppm, then fell back to 314 ppm with the onset of Spring. He corrected attributed the behavior to the fact that in Spring, plants suddenly take up a large amount of CO2, then gradually release it back to the atmosphere in Fall and Winter as the leaves fall and rot, releasing their stored carbon.

Beginning in 1958, Keeling took regular CO2 measurements at the top of Mauna Loa volcano in Hawaii. As the measurements progressed over the years, Keeling noted a steady increase of about 1.5 ppm per year. His plot of the increase, now called the "Keeling Curve", represents the most telling evidence of human impact on Earth's climate. While many other scientific findings on global climate change have come under attack, no one has challenged the steady and significant increase in CO2 found by Dr. Keeling--an increase solely attributable to human-caused burning of fossil fuels.

"I don't think I'm aware of any controversy about Dave's measurements, and that's really kind of remarkable," said Dr. Walter Munk, an oceanographer and colleague of Dr. Keeling at Scripps for 30 years, in an interview with CNN. "Dave was a stickler for every detail in connection with his experimental work."

The Keeling Curve continues it inexorable march upward at 1.5 ppm per year, and was at 378 ppm at the end of 2004. The rate of increase took an unexpected jump to 2.4 ppm per year for the years 2002 and 2003, sparking fears that a major change in emissions had transpired. But the Keeling Curve returned back to normal for 2004, with another 1.5 ppm increase in CO2. Scientists attributed the 2-year increase to natural processes, possibly tied to droughts and fires, or such factors as global temperatures, rainfall amounts and volcanic eruptions. In 1996, Dr. Keeling and colleagues showed that seasonal swings of carbon dioxide levels in the Northern Hemisphere were becoming larger, possibly a sign that the growing season is beginning earlier because of global warming.

One humorous note, taken from Gale Christianson's interesting 1999 book, Greenhouse: The 200-year Story of Global Warming, relates the story of CO2 measurements Keeling took in California during 1955. He traveled all across the West Coast, taking CO2 measurents in remote mountainous areas. He kept all his notes and measurements in a thick green notebook, and awoke horrified one night in Yosemite National Park to find a hungry mule deer scampering away from his campsite with the precious notebook clutched in its teeth. Keeling charged out into the snow-covered woods with his flashlight, desperately seeking the notebook with months of irreplacable data in it. Finally, a glint of color caught his eye, and he found his notebook, binding torn away and pages indented by a large set of teeth. He repaired the damage with a few strips of tape and was back in business. The moral of the story: back up your hard drive!

Charles David Keeling was born in Scranton Pa, earned his bachelor's degree in chemistry from the University of Illinois in 1948 and his doctorate in chemistry from Northwestern University in 1954. Dr. Keeling was elected to the National Academy of Sciences in 1994 and received the National Medal of Science in 2002.

Dr. Jeff Masters

Climate Change

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Curious why the jump mentioned in 2003-2004 is not shown in the curve and what allowed this jump to be absorbed but not the normal build-up. Don't know if I agree on the automatic assumption that this increase is due to the burning of fossil fuels since we've increased our consumption a great deal since the 50's, yet the curve is amazingly linear (much more linear than data I get in my work). Therefore there is nothing to indicate that it has not been linear for some time (even well before the time he started taking data).
who cares.
You are a jerk
You don't speak for everyone. There are people who are interested in this information even if you are not. Who cares? I do, and you don't speak for me!
Can anyone say, "PROPAGANDA,". I knew you could.