Balzan Preis 1986 für Ozeanographie/Klimatologie
Dankesrede – Rom, 19.11.1986 (englisch)
Members of the Balzan Foundation,
I am greatly honored to be chosen as a recipient of the magnificent prize awarded by the Balzan Foundation. It is especially gratifying that you have recognized my lifetime of work in oceanography and climatology, for these scientific disciplines have not hitherto received much international recognition. And I am pleased that the prize is being awarded here in Rome, the ancient city which was the principal wellspring of our western civilization and is today one of the most fascinating cities in the world.
My wife and I and our children have had a long love affairs with Italy, ever since 1948 when we first visited this beautiful country. On that first visit, our twelve-year-old middle daughter decided that ltaly should be her country. As soon as she was able to do so she returned to Italy to spend a year of university study here. In Florence she met the young medical student from Assisi who became her husband and the father of her three children. One of those children is now a Fulbright scholar, studying Italian constitutional law in the University of Perugia.
In former times, most oceanographers received their advanced education in the fundamental disciplines of mathematics, physics, chemistry, biology, geology, or engineering. When I received my doctors degree from the University of California in 1936, after five years as a graduate student at the Scripps Institution of Oceanography, I was among the few whose degree was actually designated as being in oceanography. Part of my research had been an analysis of the buffer mechanism of sea water, the system of carbonate and bicarbonate ions and free carbon dioxide, plus minor amounts of ions of boric and other weak acids, which controls the hydrogen ion concentration in the sea. I had also worked, in part with R.H. Fleming, on the solubility of calcium carbonate as a function of temperature, salinity and hydrostatic pressure in the subsurface and deep waters of the ocean.
This work proved useful more than twenty years later, when several of us at the Scripps Institution became interested in the likelihood that carbon dioxide was increasing in the atmosphere from the combustion of fossil fuels. This had been suggested by Svante Arrhenius in the late 1890s, and in more recent years by George Callendar and Gilbert Plass. My Scripps Institution colleague, Hans Suess, had speculated that the deficiency of carbon 14 in tree rings formed before the atomic bomb tests in the late 1940s and early 1950s might be explained by the absence of carbon 14 in the carbon from fossil fuels that had been added to the atmosphere. But all these workers were puzzled by their belief that nearly all the carbon dioxide produced by fossil fuel combustion should be absorbed in the sea, since the oceans contain sixty times as much carbon dioxide as the atmosphere. I was able to show that because of the peculiar buffer mechanism of sea water, about half of the carbon dioxide from fossil fuel combustion should remain in the atmosphere, where it might have profound climatic effects, in spite of the great disproportion between atmospheric and oceanic CO2.
Suess and I published a paper in 1957 on the probable secular increase in atmospheric carbon dioxide, in which we stated that mankind, in spite of itself, was conducting a great geophysical experiment. This statement has been widely quoted in subsequent years.
The International Geophysical Year was just starting in 1957 and, in order to begin to understand the «great experiment», it was agreed that one of the projects in the IGY should be precise measurements of atmospheric CO2. These had never really been made before. I recruited a young postdoctoral student from CalTech, Charles David Keeling, who began to make continuous measurements of CO2 on the top of Mauna Loa in the Hawaiian Islands and at the South Pole, with a very high precision of a few tenths of a part per million. Re has continued these measurements ever since, and has shown that during these 28 years the carbon dioxide content of the atmosphere has increased by nearly 25%. The «Keeling curve» of atmospheric CO2 concentration at Mauna Loa, plotted against time, represents perhaps the most famous time series of environmental measurements ever made. From it we can deduce that atmospheric carbon dioxide will double, compared to the 19th century values, by about 2055.
General circulation models of the atmosphere, constructed by Syukuro Manabe and his colleagues of the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, indicate that a doubling of atmospheric carbon dioxide could increase global atmospheric temperatures by 1.5 to 4.5°C, with an even greater increase in higher latitudes. Such an increase would be an unprecedented climate change relative to conditions during the last 10,000 years.
Since 1977 it has been realized that carbon dioxide is not the only «greenhouse gas» which is increasing in concentration in the lower atmosphere. Other such gases include methane, nitrous oxide, the «freons», and tropospheric ozone, and it is now believed that an «equivalent doubling» of CO2 Is likely to take place by the year 2030, less than 45 years from now. Suess’s and my «great geophysical experiment» is being considerably speeded up by human action.
In my lifetime in oceanography I have been involved with many aspects of the marine sciences: with measuring the heat flow through the sea floor from the interior of the earth, in collaboration with Sir Edward Bullard and Arthur Maxwell; with organizing, leading, or arranging major ocean geological and geophysical expeditions to study the earth beneath the sea, in which the ships of the Scripps Institution have travelled several million miles; and with improving arrangements for international cooperation in oceanography through the organization of the Scientific Committee on Oceanic Research and UNESCO’s Intergovernmental Oceanographic Commission. But my longest continuous involvement with one subject has been with oceanic and atmospheric carbon dioxide. Even so, it Is obvious that I shall not live to see the full effects of this «great experiment».
Let me again express my profound appreciation and that of my family and friends for the great honor you have bestowed upon me. Before closing, I also want to state my deep gratitude to the scientists who have influenced me most: Harald Sverdrup, the great Norwegian oceanographer; Walter Munk of the Scripps Institution of Oceanography, my friend and colleague for nearly fifty years; and Alfred Woodford, professor of geology at Pomona College, who first brought me into the world of science.