THERE are only ever a small number of scientists who can explain a phenomenon from first principles and these experts will often speak in jargon that is unintelligible. But every so often one comes across a real expert who appears to not only have a deep understanding of a subject area, but can also write with clarity on that subject.
The oceanographer the late Robert E. Stevenson  wrote a short article for Science and Technology Magazine in 2000 disputing the popular consensus on how the oceans warm . In the following extract from ‘Yes, the Ocean has Warmed; No, It’s Not Global Warming’, Dr Stevenson claims that:
1. Sunlight directly heats the ocean to a certain depth, up to 100 metres;
2. The ocean heat balance is maintained by heat loss to the atmosphere, not to the deep ocean; and
3. Infrared radiation from greenhouse gases heats only the top few millimetres of the ocean and as a consequence is soon dissipated by evaporation.
Quoting Dr Stevenson:
“Warming the ocean is not a simple matter, not like heating a small glass of water. The first thing to remember is that the ocean is not warmed by the overlying air.
Let’s begin with radiant energy from two sources: sunlight, and infrared radiation, the latter emitted from the “greenhouse” gases (water vapor, carbon dioxide, methane, and various others) in the lower atmosphere. Sunlight penetrates the water surface readily, and directly heats the ocean up to a certain depth. Around 3 percent of the radiation from the Sun reaches a depth of about 100 meters.
The top layer of the ocean to that depth warms up easily under sunlight. Below 100 meters, however, little radiant energy remains. The ocean becomes progressively darker and colder as the depth increases. It is typical for the ocean temperature in Hawaii to be 26°C (78°F) at the surface, and 15°C (59°F) at a depth of 150 meters.
The infrared radiation penetrates but a few millimeters into the ocean. This means that the greenhouse radiation from the atmosphere affects only the top few millimeters of the ocean. Water just a few centimeters deep receives none of the direct effect of the infrared thermal energy from the atmosphere! Further, it is in those top few millimeters in which evaporation takes places. So whatever infrared energy may reach the ocean as a result of the greenhouse effect is soon dissipated.
The concept proposed in some predictive models is that any anomalous heat in the mixed layer of the ocean (the upper 100 meters) might be lost to the deep ocean. There have been a number of studies in which this process has been addressed (Nakamura 1997; Tanimoto 1993; Trenberth 1994; Watanabi 1994; and White 1998). It is clear that solar-related variations in mixed-layer temperatures penetrate to between 80 to 160 meters, the average depth of the main pycnocline (density discontinuity) in the global ocean. Below these depths, temperature fluctuations become uncorrelated with solar signals, deeper penetration being restrained by the stratified barrier of the pycnocline.
Consequently, anomalous heat associated with changing solar irradiance is stored in the upper 100 meters. The heat balance is maintained by heat loss to the atmosphere, not to the deep ocean.”
Resolving these issues is fundamental to understanding not only global warming but also the topical and related issue of ocean acidification.
1. How Scientific Ideas Become Fashionable (Part 1)
2. Robert Stevenson received a Ph.D. degree in oceanography from the University of Southern California in 1954.
1953-59 Director of Inshore Research, Hancock Foundation, USC
1959 Special Research Oceanographer, U.S. Office of Naval Research, London, England
1961-63 Research Scientist in the Dept. of Oceanography and Director of the Marine Lab, Texas A&M University
1963-65 Research Scientist, Oceanographic Institute, and Associate Professor, Depts. of Geology and Meteorology, Florida State University
1965-70 Assistant Laboratory Director and Acting Laboratory Director, Bureau of Commercial Fisheries, Biological Laboratory, Galveston, Tex.
1970-85 Scientific Liaison Officer, Office of Naval Research, SIO, La Jolla
1985-88 Scientific Liaison Officer and Deputy Director, Space Oceanography, ONR, SIO, La Jolla
From his NASA-Gemini days in the 1960s to the present time, Stevenson served as an oceanographer consultant to many astronauts.
In 1987 Stevenson was appointed the Secretary General of the International Association for the Physical Sciences of the Oceans (IAPSO) and served an eight-year term. In this position, he brought oceanographers from around the world together to share knowledge in support of oceanographic research. He organized and conducted two major International Scientific Oceanographic Assemblies as part of the International Union of Geodesy and Geophysics, in Vienna in 1991, and in Honolulu in 1995. In addition to working as Secretary General for IAPSO, Stevenson continued to work as a consultant to NASA instructing astronauts on earth observation from space.
3. Yes, the Ocean Has Warmed: No, It’s Not ‘Global Warming’ by Robert E. Stevenson
In 21st Century Science and Technology Magazine, Summer 2000