DEEP BLUE SEA
John L. Daly
The Earth is essentially a water planet.
Over 70% of its surface area is covered by oceans, seas, and lakes, while a further 5% or so is covered by glaciers and ice caps resting on land areas. More than two-thirds of this water area is located in the southern hemisphere, and the ocean masses are typically 4 to 5 kilometres deep. With the Earth being over 75% covered by water in one form or another, it follows that the response of this 75% to any increase in greenhouse gases will be decisive in determining to what extent a warming, if any, will occur.
The atmosphere cannot warm until the underlying surface warms first. This is because the transparency of the atmosphere to solar radiation, (which is a key element in the greenhouse warming scenario), prevents the lower atmosphere itself being significantly warmed by direct sunlight alone.
The surface atmosphere therefore gets its warmth from direct contact with the oceans, from infra-red radiation off its surface being absorbed by greenhouse gases, and from the removal of latent heat from the ocean through evaporation. This means, therefore, that the temperature of the lower atmosphere is largely determined by the temperature of the ocean. In other words, it is necessary for the oceans to warm up first before the overlying atmosphere can warm.
Inland locations are less restrained by the oceans and thus experience a wider temperature range. However, land cannot store heat for very long, which is why hot days in desert regions are quickly followed by cold nights. However, in terms of global averages, the more dominant ocean temperature fixes the air temperature for most of the Earth. There are several reasons for this. -
1) The oceans transport heat around the globe via massive ocean currents which sweep in grand circulations around the various oceans. The effect is to keep the tropics cooler than they would otherwise be, and to keep high latitudes warmer. The global circulation of heat in the oceans tends to moderate the extremes of hot and cold that would otherwise occur in many parts of the world.
2) Due to the high density of the oceans, a mere two metres depth of water can contain the entire heat of the atmosphere above. This enonrmous storage capacity enables the oceans to "buffer" any major deviations in temperature, moderating both heat waves and cold waves alike. Land, by contrast, has very little heat storage capacity.
3) The oceans are evaporating all the time. This is very strong in the tropics, and weakest near the poles. The effect of evaporation is to cool the oceans, and thereby cool the surface atmosphere. The removed heat reappears when clouds condense at high altitude, and above the main greenhouse traps.
The slight cooling of -0.1 deg at Thursday Island, Queensland, (lat 11 deg S) since the early 1950's, in spite of steadily rising greenhouse gases is indicative of the ocean's ability to remain cool through evaporation, in spite of actual or theoretical changes in energy inputs to the oceans, and lends support to Newell & Dopplick's (1979) calculations that tropical temperatures cannot rise any further.
OCEAN HEAT INERTIA
Greenhouse scientists are very defensive about the absence of observational evidence to support the predictions of their computer models. Consequently, considerable attention has been given to somehow account for the lack warming so far this century which the models themselves say should be upon us by now. The actual warming this century is claimed by the IPCC (1995) to be about +0.3 to +0.6 deg.C. However, the models indicate we should be +1.5 deg warmer by now.
This must be viewed in the context of increased solar radiance over the same period, an effect which must give a warming of at least +0.15 deg.C independently of any other knock-on effects. Thus, the increase in temperature is probably quite natural, and quite unrelated to Greenhouse at all. However, the computer models' prediction of a global temperature increase of about +1.5 deg by now due to Greenhouse alone, stands in stark contrast to the IPCC estimate nearly six times smaller than that predicted by the models.
The modelers have, however, produced an answer of sorts. They claim that the accumulated heat generated by greenhouse warming is being stored in the deep oceans, and that it will eventually come back out and haunt us at a later time. In other words, the warming has been merely deferred, but not cancelled.
Fifteen years ago, most scientists accepted that the "ocean lag time" for heat storage was "a decade or so". Hunt & Wells (1979) suggested only 8 years. Hoffert et al. (1980) suggested 8 to 20 years to achieve 63% of equilibrium warming. Offenborn & Grassl (1981) said it was 10 years. In 1984, Schlesinger & Gates had extended the lag time to 75 years for 63% of equilibrium warming.
By 1985, Tom Wigley of CRU was blaming the lack of sufficient warming on what he claimed were earlier misunderstandings and under-estimates of ocean heat inertia. He went on to claim that his CRU estimate of +0.5 deg. warming since 1880 was still "compatible with" the CO2 changes over the same period.
By 1989, Ann Henderson-Sellers was talking in terms of 100 years, and hinted that it might even be as much as 500 years. In effect, the lack of sufficient global warming this century has not caused the modelers to question their theoretical assumptions, or their models, but merely to seek excuses.
Longer and longer ocean lag times have therefore become a stock Greenhouse assumption created solely by the need to prop up the Greenhouse warming theory, but without any observational evidence to support this assertion.
Kevin Trenberth of the National Center for Atmospheric Research (NCAR), Boulder, Colorado, stated in 1989, that the heat storage capacity of the oceans was so enormous, that the stored heat of the whole atmosphere could be contained in the top one to two metres of the oceans. In other words, if a +1 deg temperature increase in atmospheric temperature was put into the sea, it would only warm the top metre or so of ocean. The oceans therefore have an almost unlimited `heat sink' capacity, being deeper than 4 kilometres in many places.
This enormous heat storage capacity has induced an unshakeable belief in exactly this mechanism. However, simply because the oceans can theoretically hold almost unlimited heat does not mean they are actually doing so. As we shall now see, surplus heat collected by the ocean surface from the sun or greenhouse effect remains at the surface, and becomes quickly apparent.
In 1988, an MIT research team (Hsung, Newell, & Zhongxiang) concluded that the ocean surface has not warmed at all since 1940, and that only +0.2 deg. warming is evident since 1860, (reflecting the pre-war warming). In other words, the oceans have not been storing away the missing heat. Rather, it looks as though there is no missing heat.
HOW THE OCEANS GET WARM
Warming an ocean is not as simple a matter as heating a small mass of water. The sheer depth and distribution of the ocean means that the water will not be heated equally in all places. The vast areas of the oceans cause enormous heat loss through evaporation, enthalpy (direct contact with the air) and radiation. The oceans also collect more heat in some places than in others, and so on.
So, we will begin with Radiation.
The oceans receive radiant energy from two sources, namely, sunlight and infra-red radiation re-emitted from the greenhouse gases in the lower atmosphere. Even here, we have a complication. Sunlight penetrates the water readily, and thus directly heats the ocean to a considerable depth.
About 3% of the energy from sunlight entering the ocean reaches a depth of about 100 metres, and so we have a tendency for the entire top 100 metres of the ocean to warm up easily under sunlight. However, below 100 metres, there is very little radiant energy left as the ocean depths become darker and darker, the deeper one goes. In this context, darker also means colder. as the cold deeps receive no sunlight at all.
Fig 1 - Radiation Spectrum of the Oceans at various depths
Reference to fig 1 also shows another curious feature. Visible light is at short wavelengths, and sea water is partly transparent to the visible wavelengths as the chart indicates. However, once we move into the infra-red portion of the spectrum, we find that water becomes progressively more opaque to infra-red, which is only able to penetrate a few millimetres at most.
This means that greenhouse radiation from the atmosphere, can only affect the top few millimetres of the ocean, thus heating it, while water only a few centimetres deep feels no direct effect from this type of radiation.
However, the heating of the ocean surface from infra-red energy does find its way into deeper water through the natural mixing which occurs from wave action caused by friction with the atmosphere. Even so, the ability of sunlight to penetrate the water enables its energy to be more efficiently mixed into the ocean than is the case with infra-red, which is totally dependent on wave mixing to spread its heat around. On very calm days, common in the tropics, wave mixing may be completely absent.
The equatorial regions of the oceans (ie. a band about 8 degrees latitude either side of the equator) receives the greatest amount of radiant energy, and yet this region is also known as the "Doldrums" where heat mixing through wave action is at it's weakest, due to the light airs there. This region does not even suffer from tropical cyclones. For this reason, infra-red back radiation from the greenhouse effect would not heat the sea to any significant depth, resulting instead in the energy being consumed entirely in evaporation from the sea surface.
Below about 100 metres, sunlight is too feeble to impart much heat, while surface mixing from wave action has little effect below this depth, either at the relatively calm equator, or at the more turbulent mid to high latitudes.
From the foregoing, we could conclude that the surface region of the ocean (ie. above 100 metres depth) would heat up readily in response to the sun and the greenhouse effect, on a global basis, while the deeper oceans would remain very cold, even in the tropics.
This is exactly what happens.
The surface regions do heat up readily, depending on latitude, so that we find the equatorial oceans typically warm to 27 - 28 degs, while the open oceans near the polar regions may be only 1 - 2 deg. Interestingly, the deep oceans are at about the same temperature everywhere, whether tropics or poles, at around 1 - 2 deg C.
Fig. 2 - Profile of ocean surface temperature in the Pacific
We are all familiar with the tendency for temperature differences in air causing an "overturning" effect, where warm and cold air will spontaneously set up a circulation, mixing in the heat. It is this process which drives our weather systems.
However, sea water does not behave that way.
Warm water is less dense than cold water. This means that a "cell" of warm water in a cold water environment will behave as if it were like oil, or any other less dense liquid - it will float to the surface and stay there. Since only the surface region of the ocean is warmed by the sun or greenhouse effect, there is no physical reason for that warm surface water to sink and heat the depths. Indeed, the contrary effect happens -
The warmer surface water gets, the more it resists sinking.
Even if the greenhouse effect were to warm the surface oceans, we would be able to detect this very quickly, because the acquired heat would not disappear into the deep oceans as suggested by greenhouse promoters, but rather sit on the ocean surface like a warm oil slick as shown in fig. 2.
Any owner of a backyard swimming pool will be familiar with the tendency of the top few centimetres of the undisturbed water being much warmer than the underlying water on a summers day. This is caused by exactly the same process of warm water resisting any mixing with colder water beneath. The oceans behave in precisely the same way.
In the tropics, where the surface is above 25 deg, reaching 28 deg near the equator, any extra energy absorbed by the top few millimetres of ocean from the greenhouse effect, is quickly converted into evaporation which removes this excess heat. This leaves ocean temperature largely unchanged. However, in mid latitudes, where not all energy would be consumed this way, the ocean surface would warm slightly, and be mixed into the surface layers through wave action.
We would notice this right away, since the warm surface water would now become increasingly separated from the colder deeper ocean, with less and less tendency for mixing between the two. In effect, the warming of the surface oceans, due to greenhouse warming, would be detectable in as little as a few months, let alone 500 years.
In fact, ocean surface temperature varies in some places up to 10 degrees between summer and winter, lagging the sun by only 2 to 3 months. This quick seasonal response alone tells us that there is no mysterious 500 year thermal inertia holding back global warming. If warming was underway, the mid-latitude oceans would show it fairly quickly. Even sun-worshippers on resort beaches can readily tell the difference between the sea temperature in summer compared with winter.
Fig. 3 - Ocean Temperature Seasonal Changes
Allowing for other inertia effects such as ocean currents and evaporation, the estimates agreed to by climatologists several years ago, namely that ocean lag time was only about 8 to 10 years, is not only more realistic but is also a more-than-generous estimate of the time it would take for greenhouse warming to overcome thermal inertia in the oceans.
The only reason a 100 - 500 year lag time is now being peddled around by greenhouse promoters is their percieved need to explain away the lack of warming so far, and to preserve, at any cost, the greenhouse warming theory and the bloated industry it has spawned.
There is no evidence, either in theory or in physics to support those claims.
If further proof was needed of this separation between the warm surface waters and the cold deeps, one need only look at the mean temperature of the ocean and the global mean temperature of the atmosphere near the Earth's surface. While the atmosphere is +15 deg, the mean temperature of the whole ocean is only about +3 deg.
Had the greenhouse scientists been right about the thermal behaviour of the oceans, the mean temperature of the whole oceans would now be about the same as atmospheric temperature. Instead, we find that only the ocean surface (ie. the top 100 metres) is at or near atmospheric temperatures. The rest of the oceans down to 5 kilometres are up to 12 degrees colder.
Since it is about 11,000 years since the end of the last ice age, there has been ample time for the whole oceans to warm up to the atmospheric level, even if we believed Henderson-Seller's suggested lag time of 500 years. The only reason the deep oceans have not warmed up to the atmospheric level, is because of the thermal decoupling between warm surface water and cold deep water.
The warmer the surface gets, the more is it physically cut off from the deeps.
Even though the density difference between warm surface waters and the cold deeps prevent their mixing, this separation between them does not apply when surface waters become colder than the deep waters beneath. This only happens near the polar regions where accelerated radiation from the surface through a weakened water vapour greenhouse makes the surface very cold, colder than the deeper waters beneath. In this situation, it is the deep waters, being warmer, which rises to the surface in the form of upwelling, while the warmer surface waters sink to the depths.
It is only in the frigid polar oceans that we get a significant exchange between surface and deep waters, and is part of a global vertical circulation pattern known as "Thermohaline Circulation". Since only very cold surface water is able to sink in this way, it follows that the deep ocean can never warm up, regardless as to how warm the surface ocean may get elsewhere in the world.
Thermohaline circulation is the only mechanism in theory by which a significant "thermal lag" in the oceans could arise. However, the requirement that surface water can only sink to the deeps when the surface is already very cold precludes any ability for this form of circulation to store away surplus heat generated by global warming.
The thermohaline circulation also gives rise to the "Global Conveyor", which is a slow deep sea flow of water running the length of the Atlantic oceans, the Indian and Southern Oceans, and into the Pacific. It is really a displacement effect so that water sinking in one place, must force deep water to the surface somewhere else simply to maintain sea level. The "somewhere else" is in the eastern Pacific Ocean.
This Global Conveyor has two components, namely a flow at the ocean surface balanced by a similar flow in the deep ocean moving in the opposite direction. The Conveyor is very slow and ponderous, but also very large - about 20 times the size of all the worlds rivers combined. It is estimated that the Conveyor is so slow, that it takes several thousand years for water which sinks in the polar regions to resurface again somewhere else on the Conveyor.
As the Conveyor brings warmer surface water from the tropics into the high North Atlantic, the rapid cooling of the surface ocean due to radiation causes it to become colder than the deep water, and results in its sinking, which then displaces that deeper water to create the Conveyor movement.
Both the Thermohaline Circulation, and the heat Conveyor which it creates, are both generated by the density differences between surface and deep waters when both are very cold. In addition, the salinity (or saltiness) of the water affects the density of sea water, so that density-driven circulation can be caused by both temperature differences and salinity differences between surface and deep water.
What goes down in one place must come up again somewhere else.
The Conveyor loop is closed when the displaced deep water is forced back to the surface somewhere else in the world in order to balance the volume of water sinking in the North Atlantic. This happens mainly in the eastern Pacific, and causes this particular region to have an ocean surface temperature about 8 to 10 degrees cooler than it should be, given its location near the Equator.
"EL NINO" ("The Boy")
The forced upwelling of cold deep water near South America is the source of the "El Nino" phenomenon. The rate of upwelling is not constant, but varies from year to year. When the upwelling weakens, or even stops altogether, we get a rapid warming of the surface waters to temperatures closer to the normal equatorial level, a rise of about 8 degrees.
The effect of this temperature surge is both global and immediate. South America experiences enhanced rainfall, while parts of the USA and eastern Australia experience drought conditions. Global mean temperature may rise by about +0.3 deg for the duration of the phenomenon, a warming concentrated mainly in low to mid latitudes. Weather patterns are dramatically altered all round the world, with the subsequent winters in high latitudes often becoming colder and more severe than usual.
An El Nino event usually reaches its greatest intensity late in the year and occurs about once every four to seven years, the most recent being in 1982-83, 1986-87, 1991-92, 1994-95, and the ongoing one this year in 1997. The 1982-83 El Nino was perhaps the most intense in recent times, resulting in major droughts in the USA and Australia, and led indirectly to the "Ash Wednesday" bushfire disaster in southeastern Australia in 1983.
When an El Nino event ends, the upwelling of cold deep water near South America strengthens, restoring the climate to normal again. However, if the upwelling becomes even stronger than usual, we get a phenomenon quite the opposite to El Nino, ie. an expansion of the cooler surface waters in the eastern Pacific, causing a global cooling, increased rainfall in Australia (often accompanied by severe flooding), and drought in South America.
This reversal of El Nino is called "La Nina" ("The Girl"), the most recent severe occurrence of which was in late 1988, when the world experienced a sharp cooling. There was another moderate La Nina during most of 1996.
El Nino is named after a Peruvian Christmas festival, where "The Boy", El Nino or the Christ-child, arrives in the world. At around the same time of year about once or twice per decade, the climatic phenomenon we call the Southern Oscillation also begins. The Peruvians named the phenomenon "El Nino", due to the coincidence of these dates. However, the reverse of the phenomenon was initially called "Anti-El Nino", until it was realised that this could be literally translated to mean the "Anti-Christ"!. To avoid this connotation, it was renamed "La Nina", or "The Girl".
Recent studies indicate that the cycling between El Nino and La Nina events has been occurring on a regular basis since records began, and is thus a quite normal feature of global climate. Since it is a cyclic phenomenon, it is referred to by climatologists as the "El Nino Southern Oscillation", or "ENSO" for short. ENSO is the most visible climatic impact of variable thermohaline circulation in the oceans.
THE CLIMATE "SWITCH"
The last ice age ended just over 11,000 years ago, with a rise in global mean temperature of about +5 deg, accompanied by a rapid melting of the great ice sheets over North America and Europe. The melt-waters caused massive run-off, resulting in major floodings throughout Europe and in the Mississippi Basin. In addition, the sea levels rose by over 100 metres. It is little wonder that legends of a "great flood" abound in the cultures of practically every people around the world.
Then, about 10,700 years ago, a dramatic event occurred, the details of which are only now being slowly pieced together by palaeo-climatologists. The full story is still incomplete, but this is how the sequence of events is presently believed to have occurred -.
As the ice melted, the North Atlantic became increasingly less salty, as the massive fresh-water run-off from the ice sheets poured trillions of tons of fresh water into the ocean. As stated before, water density is a product not only of temperature, but also of salinity. As the North Atlantic became less and less salty, its density became dramatically reduced, to the point where the surface waters in the far North Atlantic were unable to sink to the deeps, in spite of being colder than the deep water beneath.
In other words, the change in salinity had completely overcome the normal density differences between cold surface waters and the warmer deep waters near the polar regions, and interrupted the normal thermohaline circulation in the polar and sub- polar regions.
The Global Conveyor was stopped dead in its tracks.
Without the Conveyor to allow warm waters to flow north, the North Atlantic rapidly cooled through radiation, with an equally rapid spread of sea ice, especially given that the now fresher waters of the North Atlantic had a higher freezing point than the -2 deg normal for sea water.
The globe, especially the northern hemisphere, plunged right back into ice age conditions with breathtaking speed, an event known as the "Younger Dryas".
Several centuries later, the changing orbital geometry of the Earth which caused the end of the main ice age, continued to force the climate into a warmer mode, eventually overcoming the Younger Dryas. Once this had happened, the continued erosion of glacier and sheet ice had eventually slowed down the melt-water run-off, making the North Atlantic salty again. The Conveyor finally resumed its flow, and the Younger Dryas ended as quickly as it had begun.
This event is about the only case where a climate "switch" had occurred, where climate change had been both massive and relatively sudden. The cooling of the Younger Dryas took only a few decades, lasted a few centuries, and then warmed up again equally suddenly.
The sheer speed with which the climate reverted to ice age conditions inspired a fashionable theory in the 1970's during the "imminent ice age" scare. Since the next ice age had always been assumed to be a gradual process, scientists promoting the ice age scare dreamed up the so-called "Snowblitz" theory, which basically warned that an ice age could descend upon us quite suddenly, just as it did in the Younger Dryas. Indeed, the proposed mechanism for the Snowblitz was the closing off of the warm currents from the south, caused by a halting of the Conveyor. Lurid graphics of the Snowblitz were presented to an alarmed public on Britain's BBC in 1976 in a TV documentary called "The Weather Machine".
The possibility that the Conveyor could be stopped in this way was not lost on the modern-day doomsayers, who are now speculating that if a sudden and massive freezing could be caused by the Conveyor, then why not an equally sudden and massive warming?
Wallace Broeckner of the Lamont-Doherty Geological Observatory is the foremost advocate of this view, and his speculations about the possible future behaviour of the Conveyor have inspired many environmentalists to use the spectre of sudden and massive warming to further alarm the worlds public. A British TV documentary by James Burke, titled "After The Warming", was screened worldwide in 1991, and promoted this view of a sudden onset of global warming, with the Conveyor as the primary instrument of catastrophe.
The one common feature of these warnings is that no exact mechanism is ever proposed by which the Conveyor could even do this. All we ever get are hints and innuendoes about sinister happenings in the deeps, but no coherent explanation as to how the Conveyor could do a "reverse Younger Dryas". The possibility is merely hinted at, and the active imaginations of the general public are then left to fill in the gory details. What is worse, is that such dire premonitions are presented in the media as if they had been proved by the scientific establishment, which they clearly are not. We do not even have the full story of the Younger Dryas yet, let alone any hypothetical reverse variation on it.
But let's be pessimistic for a moment, and assume that in spite of all that has been said so far about the flaws in the greenhouse warming theory, that we did indeed get the global warming as predicted by the climate models. How would that affect the Conveyor?
A warming would warm the ocean surfaces mainly in middle to high latitudes. Warmer surface water in the far North Atlantic could eventually become warm enough to offset the present density differences between the surface and deeps, resulting in a cessation of thermohaline circulation.
Thus, we could expect the Conveyor to slow down or stop again, just as it did 10,700 years ago. Some recent models predict this very outcome.
And the result? The last time the Conveyor stopped, the earth experienced a brief renewal of ice age temperatures. If it stopped again, we could expect a somewhat similar result, namely a sharp cooling of climate to levels experienced during the Little Ice Age of the 17th century. We would be unlikely to experience a cooling as severe as the Younger Dryas itself, since there are presently no major reflective ice sheets covering Europe and North America as there was then.
Far from being an instrument of accelerated heating as hinted at by Broeckner and Burke, the only possible climatic effect of a slowed-down or halted Conveyor is to cool the climate, not warm it.
Thus, the Conveyor would act to offset, or even reverse, a greenhouse warming, even if that warming were to occur at all.
DO THE OCEANS WARM THE PLANET?
The natural greenhouse effect is assumed to warm the earth by a full +33 deg from what it would otherwise be (-18 deg.C!) without greenhouse gases. This scenario makes incorrect assumptions about albedo so that the true warming is not +33 deg, but more like +20 deg. However, it must be said that even 20 deg may be an overestimate, as it ignores the heat retention effects of the oceans.
A greenhouse effect, by definition, means that the medium through which radiation passes is more transparent at visible wavelengths, but more opaque at infra-red wavelengths, thus letting in visible energy but obstructing the escape of sufficient infra-red energy to maintain thermal equilibrium without a rise in temperature.
The oceans also behave this way.
Reference to fig. 1 shows that the oceans let in visible solar radiation right down to 100 metres depth. However, the oceans cannot radiate from such depths, as infra- red radiation can only take place from the top few millimetres of ocean. Thus, the oceans are also behaving in a greenhouse-like manner, taking in heat and then trapping some of it to cause a temperature rise.
Put another way, suppose Earth was completely covered by water, while a hypothetical "twin" planet at the same distance from the sun was completely land- covered, with both planets having the same albedo. Let us also suppose that neither planet was allowed any greenhouse gases, so that the planetary temperature would be determined only by net solar radiation and the radiative effect of ocean in the one case, and land in the other.
Which "Earth" would be warmer?
The ocean-covered earth would be warmer at the ocean surface than the land-covered one, simply due to the oceans ability to collect radiant heat more efficiently than it can re-radiate it. This is because the ocean collects solar radiation in three dimensions. To maintain thermal equilibrium, the oceans must re-radiate an equal amount in the form of infra-red radiation, but can only do so from the two-dimensional surface of the ocean. This imbalance would force up the ocean temperature in order that the surface radiation alone could balance off the solar radiation being collected by both the surface and deeper waters simultaneously.
The land planet, by contrast, would absorb radiant heat in the daytime, and re- radiate it all just as quickly at night.
It is difficult to estimate how much warmer the ocean planet would be, but comparisons of data between the larger absorbed radiation and the much smaller re- emitted infra-red from the oceans, suggest that the ocean planet could be about 8 to 10 degrees warmer than the land planet. The key would be the ocean planets' inability to radiate as much heat from the ocean surface at night as it collected to 100 metres depth in the daytime.
In reality of course, the real earth is a mixture of the two, with oceans being predominant covering over 70% of the planet and with a complex atmosphere of many gases. This being the case, we can estimate that the Earth is about +6 deg warmer, simply due to the radiative imbalance in the ocean. Fortunately, the real oceans can also cool themselves by evaporation and direct heat exchange with the atmosphere.
It might be thought that infra-red back-radiation from the atmosphere to the oceans, ie. the greenhouse effect, would be a major net heat input to the oceans. However, as fig. 1 shows, infra-red energy only penetrates the first few millimetres of the water surface, most of it being then tossed straight back to the atmosphere due to surface evaporation. The remarkable constancy of tropical temperatures, in spite of wide fluctuations in energy inputs, particularly the 7% variation in solar radiation due to the earth's elliptical orbit, attests to this effect.
The relevance of these imaginary scenarios is that climate modelers are assuming that the natural greenhouse effect warms the earth a full 33 deg from -18 to +15 deg. This 33 deg assumption then sets the base-line for many other calculations about the impact of additional greenhouse gases. As we can see, the albedo error alone cuts this back from 33 to 20 deg, while the radiation imbalance of the ocean takes a further possible 6 degrees from this to make the natural greenhouse effect worth only about 14 deg, not 33 deg as assumed.
Even though the oceans have a radiation imbalance, their overall heat budget in the real world allows latent heat removal through evaporation, and direct contact with the atmosphere, to remove most of the surplus heat, (creating atmospheric water vapour in the process). Were it to be left to radiation alone to establish thermal equilibrium, the oceans would become significantly warmer, perhaps even really hot in tropical regions.
The oceans, by virtue of their enormous density and heat storage capacity, are the dominant influence on our climate. It is the heat budget and energy flows into and out of the ocean which largely determines what the global mean temperature of the surface atmosphere will settle to. These flows, especially evaporation, are quite capable of cancelling the slight effect of CO2. This is clearly evident in the tropics where there has been no temperature increase at all in spite of a 50% increase in CO2-equivalent greenhouse gases.
To single out a single variable, namely radiation through the atmosphere and associated greenhouse effect, as being the primary driving force of atmospheric and oceanic climate, is a simplistic and absurd way to view the complex interaction of forces between atmosphere, land, ocean and outer space.
Climate modeling has been concentrated mainly on the atmosphere with only a primitive representation of the ocean, some earlier models (upon which IPCC predictions were based) depicting it as a stagnant swamp. A more rational modelling approach would have been to model the oceans first, then adding the atmospheric factors. Instead, the evolution of climate models from earlier weather models has imposed an entirely atmospheric perspective on processes which are actually heavily dominated by the oceans.
FastCounter by bCentral
Return to "Still Waiting For Greenhouse"