Roger Revelle was an oceanographer and earth scientist who was instrumental in advancing the field of oceanography as a leading earth science during the post World War II era. He helped to found the International Geophysical Year (IGY) in 1958, which led to the creation of NASA, and the establishment of a cluster of South Pole research stations staffed with scientists from all over the developed world. Other discoveries by earth scientists involved with IGY were the Earth’s magnetosphere and the Van Allen radiation belts, and the mid-ocean ridges, which in turn led to the confirmation of plate tectonics and the ability to map the positions of the continents throughout Earth’s history.
Part of Roger Revelle’s activities as an oceanographer was the study of ocean chemistry and the development of an understanding of the ocean’s role as a carbon dioxide (CO2) sink. He concluded that the speed of the ocean’s ability to dissolve atmospheric carbon dioxide was determined by its temperature and alkalinity, and that an equilibrium back pressure had to be overcome in order to dissolve the increasing amount of carbon dioxide accumulating in the atmosphere due to natural processes such as volcanism and to anthropogenic sources such as the increased burning of fossil fuels to support the burgeoning population of the world. Thus, in the late 1950s, was born the science of anthropogenic climate change. A further note: A young Al Gore took a course taught by Revelle at Harvard in the late 1960s when Revelle was a visiting professor there. The seed for the eventual movie An Inconvenient Truth was planted in Al Gore's mind back in that Harvard classroom some forty years ago.
Under Revelle’s directorship and with IGY funding, the Scripps Institute of Oceanography (SIO) hired a young oceanographer and geoscientist named Charles David (Dave) Keeling in the mid to late 1950s to keep track of the build-up of carbon dioxide from a newly established SIO outpost on Mauna Loa in Hawaii. From this station high up on Mauna Loa far away from point sources of carbon dioxide emissions, such as smokestacks, factories, and power generating facilities, and upwind of the active volcano at Mauna Loa (occasionally wind shifts cause elevated readings of volcanic carbon dioxide, but these anomalous readings are filtered out of the permanent record). During the decades that followed the establishment of the SIO outpost the daily soundings for atmospheric carbon dioxide content have been entered into a continuous record known as the Keeling Curve. The curve consists of a red line (the mean) drawn through a wavy, up and down pattern that reflects the seasonal variations of CO2 over the course of each year. Over the decades since this project was initiated, the curve is clearly showing that the accumulation of carbon dioxide in the atmosphere is accelerating.
In addition to the long term increase in atmospheric carbon dioxide, Keeling’s equipment also registered some short-term phenomena which became apparent over the course or the first days, weeks, and months of the study - the diurnal variation of CO2 in the air due to plants photosynthetically taking up the gas during the day and their discharge of it at night while respiring (breathing). A further seasonal variation appeared over the months that showed decreased CO2 level due to increased aggregate photosynthesis during the summer months in the Northern Hemisphere, where most of the Earth’s continental land mass (with its rain forests, jungles, farmlands, golf courses, etc.) is located. In Northern Hemisphere winters, where the nights are long, the days short, and many trees are devoid of leaves, photosynthetic activity decreases significantly as plants respire like animals and contribute their fair share of CO2 to the atmosphere. These are the little up-and-down grey squiggles you can see when you look closely at the Keeling Curve. The squiggles go up during the Northern winters and down after the Northern summers arrive. These phenomena were either unknown or rarely thought about by geoscientists before Keeling came along.
Here is a look at the standard Keeling Curve:
Note the red line superimposed on the squiggly grey seasonal variations of CO2. The seasonal CO2 variation over one year's time is presented in zoom view in the lower right corner of the chart.
Finally, there are some aspects of this chart I will discuss in more detail in an upcoming installment in this series. Stay tuned.
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