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Post by steve on Nov 15, 2010 17:58:28 GMT
nautonnier Are you quite sure you mean what you say here!? Water in models evaporates and precipitates according to the temperature and pressure, not the CO2. It was your question Steve: "What could make water evaporation and condensation behave differently to allow it to act as its own control knob rather than as a feedback?"I just explained how in your vernacular - it is its own control knob- Water vapor in the atmosphere is NOT 'just a feedback' as I explained. Well you actually said that water vapour in models was dependent on CO2 levels. But we'll let that by. Other than that, you're talking about the off-topic idea that water will act as a negative feedback over the long term - an idea for which there is little evidence.
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Post by af4ex on Nov 15, 2010 17:59:19 GMT
> Back to the topic: Mars Greenhouse! Here are some things I'd like to discuss: 1) Mars "average surface temp": somewhere is the range 210K to 220K, what is the best estimate of this "average value" (and why is it the best)? 2) What is the expected warming due to CO2 radiative forcing? Show the derivation if you can (using Arrhenius, or whatever)? 3) How much warmth is generated by "line broadening"? Otherwise, we may assume (based on observations of the Mars Greenhouse) that CO2 GH warming accounts for little of the 33K "comfort blanket" observed on Earth (at most 5K?). In other words, I'm skeptical of the AGW assertions (even from "lukewarmers" like Roy Spencer) that Earth would freeze without CO2. I think the water vapor, clouds and other GHG's and other feedback mechanisms would still keep the planet well above freezing. Not even sure most of us would notice the difference. [Edit: Until all the plants die from lack of C02, of course, but assume, for the sake of argument, that they figure out a way to stay alive] But I could be wrong because I've haven't worked out all these details in the math. (But I'm willing to let you folks help me develop another one of those "exact climate models" for this). :-]
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Post by steve on Nov 15, 2010 18:03:22 GMT
steve: > hang on, isn't it more likely that in this case the climate model is > better than the modelling of the observations. It happens all the time that a new, "untrusted" model (digital watch) eventually replaces the old, "trusted" model (spring-wound watch). I also see the Skeptics complain that climatologists rely too much on models and not enough on "real data", as if "real" data for any historical era (including the modern era) actually existed. All of that "real" data comes from models, with the more accurate models replacing the less accurate ones. But how do we know which model of Nature to believe, if they're all just "guessing"? I agree with that 6th century BC cleric, who figured out how to tell the false prophets from the true prophets and answered that very same question: 21 “You may wonder how you can tell when a prophet's message does not come from the LORD. 22 If a prophet speaks in the name of the LORD and what he says does not come true, then it is not the LORD's message. That prophet has spoken on his own authority, and you are not to fear him. We may not all agree that God is in Nature and therefore is part of it, but the basic "algorithm" is still the same. Ok, enough philosophy and religion. Back to the topic: Mars Greenhouse! It's a nice get out clause for a god, but the models and data (and the models that analyse the data) are constantly being compared and, hopefully, improved. Neither is nor ever will be king. We will never have a good enough model such that we can stop collecting data and we will never have enough data such that the model is no longer useful for filling the gaps (leaving aside the need for forecasts and projections).
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Post by poitsplace on Nov 15, 2010 18:11:45 GMT
ENSO, PDO etc. are relatively short term cycles with limited effect. Milankovitch is an external forcing, so it is not the ocean acting as a control knob. BUT, the cycles are NOT synchronized or even of fixed duration. As the AMO, PDO, NAO, AO, etc all go in/out of phase the world's temperature goes up and down as does the distribution of heat in the oceans. Even ignoring the potential of the oceans to absorb and release heat...the synchronizations of the phases alone can probably manage the better part of a degree of warming or cooling between them.
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Post by af4ex on Nov 15, 2010 18:32:28 GMT
steve: > It's a nice get out clause for a god, ... <soapbox> I think you're missing my point. I believe that God's laws work for everyone, even if you don't believe in them (e.g. Gravity). Using that little spark of "divinity" that is in every one of us, we will asymptotically learn more and more about Nature, but never all of it. Each "solved puzzle" opens new puzzles. </soapbox> Now let's all get back O/T <whipcrack/>!
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Post by af4ex on Nov 15, 2010 21:38:59 GMT
I was going to compute the radiative forcing the way Arrhenius would have done, way back in 1896. Then it occurred to me that he might not have known anything about absorption bands etc, because that would seem to require some knowledge of quantum physics, which came somewhat later. Or did he have some empirical knowledge of the absorption in the primary CO2 band at 14k nm? Inquiring minds want to know. So I have found the 1896 paper and will see if it can still be deciphered by us "modern" folks, 114 years later: www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf
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Post by steve on Nov 16, 2010 10:25:51 GMT
ENSO, PDO etc. are relatively short term cycles with limited effect. Milankovitch is an external forcing, so it is not the ocean acting as a control knob. BUT, the cycles are NOT synchronized or even of fixed duration. As the AMO, PDO, NAO, AO, etc all go in/out of phase the world's temperature goes up and down as does the distribution of heat in the oceans. Even ignoring the potential of the oceans to absorb and release heat...the synchronizations of the phases alone can probably manage the better part of a degree of warming or cooling between them. Indeed. If we agree a degree at most, and if we agree that most of the "cycles" usually cycle over periods of no more than a few years then the oceans could lift temperatures for a few years at most. At other times they would depress temperatures - again for a few years at most. Furthermore, most of the processes that cause the oscillations cannot sustain the extreme ends of their cycles for quite obvious reasons.
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Post by steve on Nov 16, 2010 10:45:24 GMT
> Back to the topic: Mars Greenhouse! Here are some things I'd like to discuss: 1) Mars "average surface temp": somewhere is the range 210K to 220K, what is the best estimate of this "average value" (and why is it the best)? The earth is covered by thousands of stations, many of them carefully calibrated. Even with these, the absolute temperature measurement is given with a relatively wide error bar of 0.1-0.2C. Mars has two surface stations (?) - the Mars rovers. I have linked to a site that shows that the temperature at one of these stations jitters by up to 10 degrees in time scales of a few minutes. I did my best a page or so back, which is roughly the same analysis as Arrhenius P254 onwards. Roughly, Modtran shows the warmer atmosphere of the earth and the broader lines mean that emission from CO2 to earth's surface is about 100W/m^2 as compared with 12W^m^2 on Mars. Eyeballing the Modtran plot, the width of the lines accounts for half of this extra energy. Off top of head, the depths of the ice age are associated with a less than 25W/m^2 reduction in average absorbed radiation due to change in albedo from ice coverage and reduction in CO2 levels. Snowball earth conditions have existed with a perhaps 5-10% lower Total Solar Incidence (no more than 20-30W/m^2 on average) as the sun was less bright when it was younger. In other words, there is empirical support for the importance of "non-condensing" greenhouse gases - it's not all model based.
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Post by steve on Nov 16, 2010 10:51:37 GMT
steve: > It's a nice get out clause for a god, ... <soapbox> I think you're missing my point. I believe that God's laws work for everyone, even if you don't believe in them (e.g. Gravity). Using that little spark of "divinity" that is in every one of us, we will asymptotically learn more and more about Nature, but never all of it. Each "solved puzzle" opens new puzzles. </soapbox> Now let's all get back O/T <whipcrack/>! I didn't miss your point which is that the quoted sayings of gods *and* the outputs of models are both influenced by human interpretations of the world, and are therefore fallible. The fallibility of models is not disputed which is what you *seemed* to be implying, though maybe I didn't quite get your gist.
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Post by af4ex on Nov 16, 2010 12:17:30 GMT
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Post by steve on Nov 16, 2010 14:28:19 GMT
A clause in a legal contract that allows one of the parties to escape from their obligations.
cf Shimkus's pronouncement. If the world floods as a result of global warming, then God has not broken his promise, he has merely used a get out clause which Noah and his family forgot to record when the promise was made.
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Post by af4ex on Nov 16, 2010 15:29:59 GMT
Re: get out clause
I think we Americans would prefer to use the term "loophole". :-]
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Post by nautonnier on Nov 16, 2010 16:58:21 GMT
Re: get out clause I think we Americans would prefer to use the term "loophole". :-] A loophole is normally a failure to define the contractual conditions fully enough that allows a non-specified condition that is not covered by the contractual intent. A get out clause is specifically written into the contract to specify a condition that, should it apply, allows the avoidance of the contractual intent. Confusingly, a get out clause may be written into the contract deliberately but in an obscure way to allow 'get out' without the other parties to the contract realizing that a get out was possible. Perhaps I have worked too closely with the 'wrong' contract lawyers
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Post by icefisher on Nov 16, 2010 17:12:17 GMT
It's a nice get out clause for a god, but the models and data (and the models that analyse the data) are constantly being compared and, hopefully, improved. Like Ptolemy's in its worse than we thought?
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Post by poitsplace on Nov 16, 2010 19:28:33 GMT
BUT, the cycles are NOT synchronized or even of fixed duration. As the AMO, PDO, NAO, AO, etc all go in/out of phase the world's temperature goes up and down as does the distribution of heat in the oceans. Even ignoring the potential of the oceans to absorb and release heat...the synchronizations of the phases alone can probably manage the better part of a degree of warming or cooling between them. Indeed. If we agree a degree at most, and if we agree that most of the "cycles" usually cycle over periods of no more than a few years then the oceans could lift temperatures for a few years at most. At other times they would depress temperatures - again for a few years at most. Furthermore, most of the processes that cause the oscillations cannot sustain the extreme ends of their cycles for quite obvious reasons. We actually have a fairly good idea of how long the cycles are. That's the reason two of them have the word "decadal" in their names. The cycles on all of them are decades long...and the PDO has been known to take over 80 years to cycle (from proxies). Seriously Steve, I find your lack of information on this topic very telling. There are only two reasons I can imagine you wouldn't know this already from the large amount of time you've spent here on this forum. Either you have never remotely considered (or completely ignored) the vast numbers of references and explanations involving the PDO, AMO and other cycles...or outright stupidity. Which is it?
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