OUR OVEN EARTH
If the above title drew your attention then that will be because you expect me to confirm the worst fears about humanity’s goose having been cooked by anthropogenic climate change.
A goose may be cooked but not the one you would expect so please bear with me while I explain.
The ‘Oven’ analogy
The oven analogy was suggested to me by a firm proponent of anthropogenic climate change. The idea was that if one increases the insulation around an oven then it will reach a higher equilibrium temperature for the same energy input. Obviously the suggestion was that extra human greenhouse gases are analogous to extra insulation around an oven.
At first thought that seemed to be a fair and reasonable analogy but I did feel that it did not quite fit the Earth’s climate system and it took me a few minutes to work out the flaw.
The Earth may be like an oven but because Earth is exposed to space with a flow of energy out to space it is more like an oven with the door open.
So, the heating element represents the sun
the sides, top and base represent the Earth’s oceans
the air in the interior cavity represents the air around the Earth.
the flow of air in and out of the open door represents the movement of the air around Earth from surface to space as it transfers energy upwards.
1)The heating element of an oven provides the source of energy that warms up the sides, top, base and the air in the cavity. As the temperature rises towards equilibrium air moves in and out more rapidly until equilibrium is reached between the energy flow from the heating element and the flow of energy out through the open door. Unless the heat is turned up the oven will get no warmer. At that point the heat of the oven is contained primarily in the metallic or other compounds that comprise the sides top and base of the oven. The amount of heat energy contained in the air in the oven is trivial and is constantly being moved out of the oven by the circulation of the air.
2)The triviality of the heat energy in the air is important. If one were to somehow change the conductive characteristics of the air in the oven it would have no significant effect on the equilibrium temperature of the oven. However if one were to change the conductive characteristics of the sides, top and bottom then the change in equilibrium temperature would be significant.
3)So it is with the Earth. The equilibrium temperature is primarily set by the power of the sun combined with the conductive characteristics of the oceans. The contribution from the conductive characteristics of the air around us is insignificant and the contribution from a tiny component wholly irrelevant. Furthermore the energy content of the oceans seems to be in constant flux via multi decadal cycles in each ocean that change the rate of solar energy flow from ocean to air and thereby change the temperature of the air globally to an extent that regularly swamps any changes that could ever be induced by changes in the air alone.
4)Consider what happens if the equilibrium temperature of the oven increases due to more power from the heating element and/or an increase in the heat retaining capacity of the sides, top and base. Clearly there will be a rise in the equilibrium temperature but that will be accompanied by a faster flow of air in and out of the door.
5)So it is with the Earth. When the oceans release energy faster the air warms, the equatorial air masses expand, the weather systems shift poleward, energy is expelled faster to space and a new equilibrium is set until the energy flow from the oceans slows down again when the process reverses.
6)Consider now the effect on the equilibrium temperature of the entire oven by a tiny change in the conductive characteristics of the air within it. It will be negligible and will be unable to force a change in the other component namely the metallic or other compounds forming the sides, top and base of the oven. Instead the flow of air in and out of the oven will increase and neutralise any attempt by the air to alter the equilibrium temperature of the entire oven.
7)So it is with the Earth. A tiny change in the conductive characteristics of the air will not significantly alter the equilibrium temperature of the whole Earth. Instead, just as with the analogy of the oven with an open door, the flow of energy away will be accelerated and the effect of the change in the air neutralised. That acceleration of energy to space will operate by exactly the same mechanism as the air deals with changes in the energy flow from the oceans caused by shifts in the ocean cycles. The hydrological cycle will speed up and the weather systems will shift imperceptibly to deal with it.
1) The greenhouse effect of the air (the definition of atmosphere should include oceans for the purposes of this discussion) depends on the ocean only as a means of getting lots of water vapour into the air. However the greenhouse effect in the air is just an expression of the slowing down of the transmission of energy through the air and water vapour is the main cause of that slowing down. The air is only one section of the whole process that involves energy flowing from sun to oceans to air to space. The air should not be viewed in isolation. It is the slowing down of the transmission of solar energy through the entire planetary system of Earth that sets the equilibrium temperature of the planet.
2) As a separate process there is a slowing down of the transmission of energy through the oceans. That is the Hot Water Bottle Effect.
3) The slowing down effect in the oceans is so huge that it renders the slowing down effect in the air insignificant so that the equilibrium temperature of the planet is set by the oceans and not the air.
4) If WV stayed the same on a planet entirely covered by land and all else being equal the equilibrium temperature of that planet would be much less than that of Earth because the faster response time in warming up from solar energy would be matched by an equally fast loss of energy at night and in winter. The equilibrium temperature would be set by the trivial slowdown in the transmission of solar energy through the air alone and would not be increased by the much larger (indeed overwhelming) slowdown in the transmission of energy through the oceans. The air and oceans operate just like electrical resistors. If the equilibrium temperature were set by the effect of the air alone the solar energy would not have been retained on the planet long enough to reach the current temperature.
5) The temperature of the air on Earth is constantly being supplemented by a variable flow of energy from the oceans. That energy content of the oceans is set by current astronomic influences combined with past geological events and variations in solar input.
6) The oceans are a charged battery that sets and maintains the equilibrium temperature of the planet with the greenhouse effect in the air an insignificant player.
A simple, coherent and apparently accurate analogy suggesting that humans cannot significantly affect Earth’s climate by changing the amount of CO2 or other greenhouse gases in the air.
Pollution, resource depletion and other problems are a different issue but if we are to make the right long term decisions we need the correct diagnosis first.
Even if extra greenhouse gases just make it a bit warmer at the top of a natural cycle and a bit less cold at the bottom of a natural cycle then the current kerfuffle is pointless, harmful and dangerous.
In a couple of hundred years we could have the energy and population aspects peacefully and consensually dealt with yet see only a negligible, possibly not even measurable, effect from human influences on climate.Published by Stephen Wilde April 22, 2009