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August 21, 2007
The Big Heat Pipe In The Sky
The atmosphere has been described by the Profits of CO2 Doom as a blanket that traps the incoming solar energy and warms the planet. Which is true. At a short time scale. At a little longer time scale the atmosphere is more like a heat pipe. This is on the scale of weather. Day to day changes. I'm going to first explain how heat pipes work and then show how the atmosphere is similar. We will also look at how the ocean is the primary determinant of climate on longer time scales (5 years time constant). What is a heat pipe? It is a sealed metal tube (quite often copper) partially filled with a fluid that also has a wick running its full length. The wick is arranged so that it is in contact with the walls of the tube. Here is a simple diagram of a heat pipe. How does the heat pipe work? It has a cold end and a hot end. At the hot end the external heat source boils the fluid in the heat pipe the vapor created then condenses on the cold end and the wick then carries the fluid back to the hot end and the cycle repeats. Because of the evaporation/condensation method of heat transfer the temperature drop between the hot end and the cold end is much smaller than if the tube had been made of a solid piece of metal. That kind of heat transfer is very efficient. You can get into more of the details at wiki on Heat Pipes. If you want to learn a little of the math and some of the practical difficulties here is a good article on how to build a heat pipe. Let me start with an article I discussed earlier at Feedbacks Misdiagnosed. It is by Roy Spencer and discusses the nature of water vapor feedback in terms of weather and climate. Let me start out by saying that water vapor is the most prevalent and most effective greenhouse gas in our atmosphere. Here is a bit of what Roy has to say. For instance, everyone believes that water vapor feedback is positive, and conceptually justifies this by saying that a warmer surface causes more water to evaporate. But evaporation is only half the story in explaining the equilibrium concentration of atmospheric water vapor; precipitation is the other half.Which is to say that the whole heat pipe, not just the hot end, must be considered when studying the atmosphere. I covered some of that in Clouds and More Clouds and Clouds In Chambers. Roy Spencer discusses how water vapor is the atmosphere's natural air conditioner. Which is not bad. An air conditioner is in many respects a mechanized heat pipe. It can actually transfer heat from a cold space to a hot space. The atmosphere can't do this. So the heat pipe analogy is more apt. Other than that he has some good simple diagrams and pretty pictures to explain what is going on. So let me sum up: We don't live in a greenhouse. We live in a heat pipe. Actually that is not strictly true. We live in a greenhouse and a heat pipe. The greenhouse slows heat transfer by radiation. The heat pipe increases heat transfer by conduction and convection and evaporation and condensation. Because of heat storage in the ocean there is about a 5 year time constant from the time the extra energy starts coming in until balance is mostly restored. In terms of delayed response, the climate problem is similar to the capacitor soakage problem in electronics. There is a primary time constant and a number of secondary time constants. The secondary time constants are generally not very influential except at very high precisions. Even then their influence is limited to very low frequency signals. Roy Spencer and a number of others have worked out the primary time constant by other means and have also come up with a numbers around five years. In control theory to assure system stability you generally want a system where a first order lag is dominant. This appears to be the case in the climate system according to a number of different analysis methods. In addition because of water vapor evaporation/condensation the atmosphere is more like a heat pipe than a blanket at the time scales (five years) in question. At shorter time scales it is more like a blanket due to the lags. In fact the primary time constant is determined by the evaporation/condensation time constant according to Stephen E. Schwartz. I'll go into where the five year number comes from in another post (can't say when). For those of you who can't get enough on how the consensus is breaking down you might want to read this link rich piece by a Congressional staffer. Cross Posted at Power and Control posted by Simon on 08.21.07 at 08:32 AM
Comments
Simon I am so glad you included that final sentence. It gives me the opening to post an update on climate change legislation in California. http://www.sacbee.com/392/story/336242.html Also this compromise is making an ass out of Senate Pro Tem Don Perada (not hard to do), Boy I love democracy.
Papertiger · August 21, 2007 02:20 PM Tiger, When people get all nuts about "greenhouse gases" you now have a counter phrase "heat pipe gases". Note: I was last living in California in 1972 (not counting business trips). Haven't missed it at all. The "left coast" is insane. Present company excluded. M. Simon · August 21, 2007 03:03 PM Tiger, I hope with all my heart that sanity invades California some day. Soon. Every crackpot dystopic regulation ends up here. Like I want to emulate a typically lefty Californian. OregonGuy · August 21, 2007 04:14 PM What we have is even better than a 'heat pipe': we have a big old 'heat sink' at the south pole. If it were warmer it would just transmit heat into space, which is one of the reasons we do not have a Cretaceous climate. When you want to cool something off you put a big radiator on it... it radiates heat away and when there isn't much heat left it *gets cold*. The north pole doesn't have a continent under it so the water circulates under it to distribute the heat differential. The south pole, with a lovely continent, can just chill so nicely downwards and retain the heat differential. A 'heat sink'. The planet gets cooler. Before Antarctica got to near its present position we had a global climate 14 degrees warmer than now. It goes into a place where it can get *really* cold for six months out of the year and the sunshine is weak for the rest of it. Planetary temps go down, way down. Glaciation cycles start to oscillate... temps vary wildly within a restricted range. Reunite Gondwanaland! Return us to those days of 70 million years ago with warm inland seas over the continents! Let me know how that goes in the next 10-15 million years.... ajacksonian · August 21, 2007 06:54 PM "The atmosphere has been described by the Profits of CO2 Doom as a blanket that traps the incoming solar energy and warms the planet. Which is true." While it may be true that some of the "Profits of CO2 Doom" describe the atmosphere as "as a blanket that traps the incoming solar energy and warms the planet" it is not true that it does. Nor is the atmosphere a greenhouse. The atmosphere/earth system is far more complex than that. The atmosphere acts as a source of energy for the earth and vise versa. The atmosphere receives about 94% of its energy from the earth while the earth receives about 66% of its energy from the atmosphere. Blankets and greenhouses suppress convection the atmosphere faciltates convection. The earth is about 30 degrees C warmer than it would be without an atmosphere. Bill H · August 21, 2007 07:42 PM Simon I don't know what the media will say about it or even if it will be mentioned at all, but the California GOP State Senate won. We have GHG laws put off for two years. Alot can happen between now and then
Papertiger · August 22, 2007 12:44 AM Tiger, Is there any way I can get plausible deniabilty? Any way, beating people is wrong and keying cars is bad. Are you starting a defense fund? LOL Simon M. Simon · August 22, 2007 12:52 AM My guess is that the climate will have cooled some more and it will be put off another few years. Eventually the legislature will forget to vote on the subject. M. Simon · August 22, 2007 12:55 AM Simon No need for bail money. The better angels of my nature prevailed. By the way, the Bee killed that story I linked. It was much too positive for the GOP in California, so flush, it goes down the memory hole. Papertiger · August 23, 2007 11:19 PM Post a comment
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Somewhere, was it grade school or high school, the idea was put forward that the environment is like a clock. Springs and wheels and thingies. If a wheel is out of balance, we can apply a small weight to bring it back into line.
I'm afraid that the complexity of the system defies attempts to bring it into the scale of watch works. When you model the climate, how can you know which variables are endogenous and which are exogenous? And better yet, how can you know whether you've overlooked an important variable?
This leads me to believe that climate concerns are more a vanity than a science. Why else the predisposition towards anthropogenic causes of global warming? It satisfies within us our need to be important. And better yet allows unrestrained meddling with any and all aspects of our lives.
The problem, of course, is that most if not all of this meddling is useless, futile and in the end, counterproductive. But balance, intelligence and patience are not noted characteristics of our political class.
Thanks for the article. It reminded me of this.