By Paul Homewood
How often have we heard the claim that the “missing heat” is hiding in the oceans?
Back in 2000, leading oceanographer, Robert Stevenson, debunked that theory:
Contrary to recent press reports that the oceans hold the still-undetected global atmospheric warming predicted by climate models, ocean warming occurs in 100-year cycles, independent of both radiative and human influences.
At a press conference in Washington, D.C., on March 24, 2000, Dr. James Baker, Administrator of the U.S. National Oceanic and Atmospheric Administration (NOAA), announced that since the late 1940s, there “has been warming to a depth of nearly 10,000 feet in the Atlantic, Pacific, and Indian Oceans.” “In each ocean basin, substantial temperature changes are occurring at much deeper depths than we previously thought,” Dr. Baker said, as indicated by research conducted at NOAA’s Ocean Climate Laboratory. He was referring to a paper published in Science magazine that day, prepared by Sydney Levitus, John Antonov, Timothy Boyer, and Cathy Stephens, of the NOAA Center.
For 15 years, modellers have tried to explain their lack of success in predicting global warming. The climate models had predicted a global temperature increase of 1.5°C by the year 2000, six times more than that which has taken place. Not discouraged, the modellers argue that the heat generated by their claimed “greenhouse warming effect” is being stored in the deep oceans, and that it will eventually come back to haunt us. They’ve needed such a boost to prop up the man-induced greenhouse warming theory, but have had no observational evidence to support it. The Levitus, et al. article is now cited as the needed support.
Science news writer Richard A. Kerr, in his “promo” article to get everyone excited about the new NOAA paper, asserts that “The ocean-induced delay in global warming also suggests to some climatologists that future temperature increases will be toward the top end of the models’ range of prediction.”
To complete the surge of enthusiasm, Dr. James Hansen of the Goddard Institute for Space Studies, argues: “Now the ocean-warming data imply that climate sensitivity [to the greenhouse effect] is not at the low end of the spectrum.” He, and some others of United Nations fame, lean toward a climate sensitivity of about 3°C or a bit higher, by the end of the century—the next century, that is.
Stevenson went on to detail the Levitus study, and then gave his thoughts:
So, How Does This Play in Hanalei?
(Considering that Hanalei, Hawaii is just down the hill from where I write, I thought I’d inject a little local color into my comments.) It sometimes seems as if I’m living in a “time-warp” in which some people, and scientists, are unaware that rational life existed before their birth—or before they got out of the sixth grade. Yet, we marine scientists did not enter the second half of the 20th century without a fair bit of understanding of the thermal ocean.
For example, Prof. Hubert H. Lamb, the premier European climatologist of the 20th century,1 wrote in 1977 that “there has been a general warming of sea temperatures, by 0.5-1.0°C, from 1880 to 1965, defined from widely scattered points around the oceans of the world.” Lamb went on to say that “This general warming is known from the Gulf of Alaska, the eastern Pacific Ocean, the western Indian Ocean, the eastern and northern North Atlantic Ocean, and the tropics of both the Atlantic and Indian oceans.”
Within those 85 years, Professor Lamb noted that there were “minima in the periods of 1915-1925 and again between 1940 and 1950”—meaning that the rate of temperature rise went to zero, but temperatures did not decline to levels lower than they had already reached. For the Atlantic Ocean, 55°N to 40°S, the waters were cooler by 0.8°C to 1.0°C in 1780-1850 than in 1950. Now, the temperatures that Professor Lamb provides were certainly not taken as precisely, nor were they as many as we have acquired in the past half century. But, their existence is not trivial…..
Sources of 20th Century Ocean Temperatures
I learned to deploy Nansen water bottles and reversing thermometers for deep-sea sampling in 1949. I spent the rest of the subsequent decade seagoing, for the most. I can’t remember how many bottle casts I made, or how many bathythermographs I deployed. There had to be thousands in the waters off coastal California. Other students and post-docs were doing the same farther offshore in the eastern Pacific, from the E.W. Scripps. In the westernmost Atlantic, a similar cadre worked from the Atlantis.
In the 1960s, more ships were out at sea: from Fisheries Laboratories, U.S. Coast and Geodetic Survey (now NOAA), and research institutions at Scripps (La Jolla, Calif.), Woods Hole (Massachusetts), Miami, and Texas A&M (in the Gulf of Mexico). The British sailed the new Discovery, the Germans the new Meteor, and there were small ships sailing from Denmark, Japan, and France. Many cruises were dedicated to the geophysics of the sea floor, where deep-ocean casts for water and temperatures were few and far between.
Surface water samples were taken routinely, however, with buckets from the deck and the ship’s engine-water intake valve. Most of the thermometers were calibrated into 1/4-degrees Fahrenheit. They came from the U.S. Navy. Galvanized iron buckets were preferred, mainly because they lasted longer than the wood and canvas. But, they had the disadvantage of cooling quickly in the winds, so that the temperature readings needed to be taken quickly. I would guess that any bucket-temperature measurement that was closer to the actual temperature by better than 0.5° was an accident, or a good guess. But then, no one ever knew whether or not it was good or bad. Everyone always considered whatever reading was made to be precise, and they still do today. The archived data used by Levitus, and a plethora of other oceanographers, were taken by me, and a whole cadre of students, post-docs, and seagoing technicians around the world. Those of us who obtained the data, are not going to be snowed by the claims of the great precision of “historical data found stored in some musty archives.”…
How the Oceans Get Warm
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.
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What about Thermohaline Circulation?
The fact that the surface ocean can become denser than the underlying waters, thereby sinking to depths of “density equilibrium,” has been discussed since surveys of the physical ocean began in the second half of the 19th century. Certainly the concept was known before HMS Challenger sailed, in 1873, on its famous expedition. One of the multitude of suggestions made by members of the Royal Society at that time was to investigate the “over-turning of surface waters caused by density differences.”
Thermohaline circulation is responsible for the formation of the bottom-water masses in the world’s oceans: the North Atlantic Deep Water (NADW) originates basically in the region of the Labrador Sea; the Weddell Sea is the source of the deep-water in the circumpolar Southern Ocean; and the Pacific Deep Water originates in the Ross Sea. In many other places in the oceans, and seas, as well, surface waters are carried into the depths by thermohaline circulation.
So, it is not surprising that those modellers who “need” to get warm surface waters to move into the depths of the oceans, and remain sequestered there for long periods of time, would turn to the physical mechanism of this vertical circulation system. Their hope (claim) is that there can be occasions when salinity, rather than temperature, is the prime determining factor in the density of the surface waters. Then, warm water, made dense by an increase in the sea’s salt content, would sink.
It does not happen!
The primary physical factor in determining the density of sea water is the temperature (Sverdrup, Johnson, and Fleming, 1943). In the open ocean, top or bottom, salinity differences are measured in a few parts per thousand. Thermohaline circulation takes place where the surface waters become colder than the waters beneath. The large vertical movements occur in polar seas, where accelerated radiation makes the surface waters greatly colder than the deeper waters.
In these waters, surface water temperatures are about -1.9°C, the normal salinity of the water keeping it from freezing into ice. The deep waters, being warmer than such surface waters, rise to the surface, as the upper layers sink slowly into the dark ocean depths. Because only very cold surface water is able to sink, it is simple to understand that the deep ocean can never warm up, regardless of how warm the surface ocean around the world may become. No deep lying “thermal lag” is going to take place. It is clear that there’ll be no Phoenix rising as a haunting specter….
So, where does the NOAA paper fit?
I was rather eager to read the article by Syd Levitus, and his colleagues. I was somewhat put-off by the headlines about “missing warming,” but I figured that was just the usual hype by the media.
Yet, here I sit in the middle of the Pacific Ocean, surrounded by papers (peer-reviewed, I guess I should add) which conclude:
(1) For the past two decades at least, and possibly for the past seven decades, the Earth’s true surface air temperature has likely experienced no net change;
(2) there should have been a sizable CO2-induced increase in atmospheric radiative forcing during that time, but there wasn’t. That must mean that a suite of compensatory feedbacks overwhelmed the “greenhouse” impetus for warming; implying, therefore,
(3) that the planet will not warm from any man-produced increases in CO2; indicating
(4) any increases in temperature will likely fit the global trend of +0.048°C/decade, that is, about 0.5°C this century— the rate of warming that has existed since the Little Ice Age, centered around 1750 in Europe, South America, and China; suggesting
(5) that the heat storage in the upper ocean takes place in the upper 100 meters, and the magnitude provides a rise in temperature at those depths of 0.5°C in the past 50 years (in those parts of the ocean for which we have data);
(6) this global warming (and cooling) of the ocean occurs on biennial, ENSO, decadal and interdecadal period scales; thence,
(7) the ocean thermal changes on centennial-period scales, which appear as the warming trend through the past 50 to 100 years, can be explained by means of intrinsic internal modes of the Earth going through their normal cycle of warming and cooling, independent of both radiative and anthropogenic influences.
I guess what I’m really wondering is “Why did Syd Levitus, and his associates, write their paper in the first place?”
Robert E. Stevenson, an oceanography consultant based in Hawaii, trains the NASA astronauts in oceanography and marine meteorology. He was Secretary General of the International Association for the Physical Science of the Oceans from 1987 to 1995, and worked as an oceanographer for the U.S. Office of Naval Research for 20 years. A member of the scientific advisory board of 21st Century, he is the author of more than 100 articles and several books, including the most widely used textbook on the natural sciences.
Eighteen years on, and nobody has managed to prove him wrong.
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October 10, 2018 at 12:37PM