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| sciman |
 Posted: Sat Dec 15, 2007 11:19 pm Post subject: green house effect |
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Forum Freshman
Joined: 23 Aug 2007
Posts: 10
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| give me some information about green house effect |
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| marnixR |
| Posted: Sun Dec 16, 2007 1:18 am Post subject: |
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Forum Isotope
Joined: 10 Apr 2007
Posts: 2584
Location: Cardiff, Wales
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sun shines on greenhouse
light falls through glass of greenhouse
light reflects as heat
heat trapped inside greenhouse
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if you find this place too crowded or too confrontational, how about trying Philosophorum,
the amicable forum where small is beautiful and even the trolls are intelligent
biology without evolution is but stamp collecting |
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| Bunbury |
| Posted: Sun Dec 16, 2007 9:55 am Post subject: Re: green house effect |
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Forum Ph.D.
Joined: 26 Sep 2007
Posts: 843
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| rjc34 |
| Posted: Sun Dec 16, 2007 1:19 pm Post subject: |
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Forum Freshman
Joined: 27 Oct 2007
Posts: 44
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sun shines through earth's atmosphere to the ground.
bounces back up to the atmosphere.
greenhouse gases (mostly water vapor) trap some of the heat so the earth doesn't turn into an ice planet. |
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| Chris |
| Posted: Wed Dec 26, 2007 6:53 pm Post subject: |
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| icu |
| Posted: Fri Feb 29, 2008 7:12 pm Post subject: |
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Forum Freshman
Joined: 28 Feb 2008
Posts: 58
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cool  |
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| andre |
| Posted: Sat Mar 01, 2008 3:23 am Post subject: |
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Forum Sophomore
Joined: 10 Aug 2007
Posts: 128
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The essence of Chris' narration is:
| Quote: |
| This page gives the formulas for forcing-responses for various GHG’s. ΔT of ~1.2 K from just 2x CO2 is very easy and based on simple physics (hint, apply the new OLR of ~3.7 W/m-2 forcing to Stefan-Boltzmann in part 1 and extrapolate ΔT). However, the literature (see IPCC, 2007) now suggests ΔT (2x CO2) is 2-4.5 K. This comes from adding positive and negative feedbacks (water vapor, ice-albedo, lapse rate, clouds, etc) which are net positive, and so responsible for the higher climate sensitivity |
First sentence is fine, no problem there. Second sentence is baloney as I will show in the coming dozen posts or so.
Let's begin with the warming for doubling CO2
Note that Myhre et al 1998 is only an estimation. When doing some calculations with the MODTRAN model based on the HITRAN absorption database, it can be shown that, with keeping absolute humidity constant, the doubling CO2 deltaT is less than one degree.
When the relative humidity is kept constant it is noted that doubling CO2 temperatures increase is indeed around 1.5 degrees, that is if somebody magically add the energy required for evaporation, since that is not in the model. So Myhre et al are some half way in between. But keeping relative humidity constant, means more water vapor which is the 'positive' feedback mechanism. So it's already incorporated. You can't add it twice.
Another problem with positive feedback as in keeping the relative humidity constant requires exponentially more energy while the additional available reradiation energy is logaritmic with increased greenhouse concentration. This makes the positive feedback fade away rapidly.
****
For checking my assertions, I did that in another thread here:
http://www.thescienceforum.com/viewtopic.php?t=10371&postdays=0&postorder=asc&start=24 |
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| Chris |
| Posted: Sat Mar 01, 2008 10:47 am Post subject: |
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Joined: 12 Oct 2007
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If you do the calculation with just holding relative humidity constant, you do not capture the full effect of any water vapor feedback. To do so you have to raise the temperature in the “Ground T Offset Box.” I would appreciate if you would stop using this MODTRAN and evaporation argument now from audience to audience; David Archer fully supports AGW within the ranges of ~3 C, and he put the model up to be used correctly. If you continue to parrot the "Evaporation energy" nonsense you are either ignorant or dishonest. My tone only gets worse everytime you post, because all of these issues have been covered in other venues, and going from forum to forum after the last place no longer buys it, is merely a sign of intellectual bankruptcy. The experts like Brian Soden and Isaac Held who sit on the mainstream of feedbacks do not need a refresher course from you.
By now andre has disproved feedbacks, he has disproved ice cores showing temperature, he has disproved our knowledge of latent heat, and the list goes on and on...his nobel is nowhere to be found |
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| andre |
| Posted: Sat Mar 01, 2008 11:00 am Post subject: |
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Joined: 10 Aug 2007
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| Chris wrote: |
| If you do the calculation with just holding relative humidity constant, you do not capture the full effect of any water vapor feedback. To do so you have to raise the temperature in the “Ground T Offset Box.” |
And by this statement, Chris, you are exposing yourself terribly. You have not even bothered to check my link so see that's exactly what I do. The rest of your post is mounting fallacy on fallacy, alternately ad homimens and appeal to authority.
BTW MODTRAN is Air Force, not Archer. It pleads for him that he still holds it up, despite it's AGW hype debunking capacity.
Why not do some science instead. Debunk for instance Olavi Kärner who demonstrates that atmospeheric feedback is negative. I haven't seen that happen yet.
http://www.aai.ee/~olavi/EE2007-ok.pdf
http://www.aai.ee/~olavi/E-Ac-Sci-07.pdf |
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| icu |
| Posted: Sat Mar 01, 2008 12:54 pm Post subject: |
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Forum Freshman
Joined: 28 Feb 2008
Posts: 58
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u can get some in wiki 
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It's ok, everyone makes mistake..... |
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| Patches1 |
| Posted: Sun Mar 02, 2008 2:06 am Post subject: |
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Forum Freshman
Joined: 22 Feb 2008
Posts: 13
Location: Australia
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You guys can carry on arguing the science until the cows come home, are milked and the latter turned into cheese or yogurt if you prefer. But until you can convince me that it matters in terms of diminishing food resources caused by over-exploitation, then it's just argument for the sake of it. What is the problem with climate change? It's happened numerous times before and with some speed. Then we had much fewer humans and they adapted. Try telling impoverished Indians or Pacific Islanders they have to eat our plastic garbage because we are too busy exploiting their sea-food resources to pay for science to test the theory of global warming caused by human activity to bother with such small things!  |
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| andre |
| Posted: Sun Mar 02, 2008 3:28 am Post subject: |
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Forum Sophomore
Joined: 10 Aug 2007
Posts: 128
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Anticipating Chris' worse tone, let's investigate those linked studies,
Amplification and feedback are often confused as being the same as in "positive-feedback-amplifies-the-greenhouse-effect-of-CO2". However, amplification is something that happens within a system (Earth reaction to radiation -Stephan Boltzman law), between forcing input signals (sun, ghg effect) and output (temperature, clouds, precipitation). Now, those outputs modify the input signals (clouds shield the sun and trap infrared), and this is called feedback.
If the effect of all the feedbacks is the same as the input forcing signals, both having a plus sign or a minus sign, then the feedback is called positive. Alternately, if the effect of the feedback is opposite the input forcings we have negative feedback. Indeed in a steady state situation with equilibrium positive feedback ultimately leads to stronger effects and negative feedback to lesser effects. But that's only in steady state, in between transitions a lot can happen.
Warming and cooling of the Earth takes time, there is the daily cycle and the yearly cycle causing the Earth always to be in transit. Remember that feedbacks are reactions after output, so they can't start working before the lag in the systems is overcome. Take for instance a nice blue sky at sunrise but after several hours of solar warming, cumulus clouds form, moderating the incoming sunshine. This is typical lagging negative feedback.
So the basic difference in effect between amplification and feedback is the lagging and in a system in transit that's a nightmare for engineers as everything appears to feedback systems including electronics in which decent negative feedback can effectivily change into positive feedback if it lags just half a cycle, so the opposite sign becomes the same sign, which can steer systems out of control in ever stronger oscillations, known as resonance.
This latter is the reason why feedback effects are very well studied and known and one would tend to wonder why there is so little about it in climatology, ok there is Held and Soden as Chris no doubt will explain, but they don't deal with transit effects, but Kärner does.
What can those transit values say about the nature of the feedback, positve or negative? Kärner explains:
http://www.aai.ee/~olavi/E-Ac-Sci-07.pdf
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...If positive correlations are dominating in the term sigma etc,
the function D(tau) has a faster growth rate than in the previous case. Positively correlated increments tend to have the same sign, so the process tends to increase in the future if it has had an increasing tendency in the past. And, vice versa, it has a tendency to decrease in the future if it has had a decreasing tendency in the past. Such a feature is called persistence (P)...
....about anit-persistence: Being negatively correlated, the increments tend to have opposite signs, so that the process has a tendency to decrease in the future if it has had an increasing tendency in the past and vice versa. The feature is called anti-persistence (AP). It expresses a tendency of the values of increments to compensate each other to prevent for the process from blowing up too fast. Such a system tends to eliminate deviations showing a negative feedback in aggregate.
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Hence (due to the lag) a positive feedback system tends to persist in a movement, opposing changes when the direction sign of the forcing function changes. This opposition delays the direction change or it even cancels the direction change when the forcing function changes direction back again before actual direction change of the system took place.
While a negative feedback (due to the lag) amplifies a change in direction of the forcing function, since it was already going that way, so it assists the change in direction, making it easier to happen even if the change of the forcing function was short in duration.
It's clear that this opposite behavior can be tested with the available climate data by comparing how many times direction changes take place between the different datapoints, the Hurst exponent. Kärner finds anti-persistency or negative feedback in the IR outgoing longwave infrared in that first study and same for long term temperature series here.
So you can model all you want, if typical anti-persistant transitient behavior is dominant it falsifies positive feedback effectively.
Now Chris, please, do show my interlectual bankruptcy. |
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| andre |
| Posted: Mon Mar 03, 2008 5:22 am Post subject: |
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Forum Sophomore
Joined: 10 Aug 2007
Posts: 128
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Let's talk a bit about
| Chris wrote: |
| My tone only gets worse everytime you post, because all of these issues have been covered in other venues, and going from forum to forum after the last place no longer buys it, is merely a sign of intellectual bankruptcy. |
When I brought up the Kärner studies the other year in a forum which Chris also visits, only these two where available proving the typical non-persistent reactions of temperature in the atmosphere.
http://www.aai.ee/~olavi/2001JD002024u.pdf
http://www.aai.ee/~olavi/cejpokfin.pdf
So somebody else "rebuted" this by remarking that the satellite series, which Kärner used, had been revised, so his studies were no longer valid so he was to be wrong.
I replied that the corrections were limited and generally in one direction, which would be negliglibe when looking at the deltas only. Andit could hardly affect if at all, the main principle of counting the heading reversals in the random walk. (Few is positive feedback, many is negative feedback). Moreover, I said, if the new satellite data would have led to proof for positive feedback, then where is the study that shouts: "Final and Unambigous Definite Concluding Evidence for AGW; Satellites Proofs Positive feedback"? There is no doubt in the world that nobody could have overlooked the existence of such a study. Consequently, even with corrected data, it's highly unlikely that it would change the outcome of antipersistancy.
So I mailed Kärner about the data problem and he promptly reacted with the new study mentioned before. So when I posted that somewhere, (not sure if Chris was around then), the "rebutal" was: why only 24 stations in Europe and Asia. cherry picking? If you don't use all the station you have nothing.
to that I responded that he was looking for a principle (rate of heading reversals), and not about finding average global numbers. If the principle shows up at every possible occasion, how many records would you need? After all it's 24 times more than the first study and for an order of magnitude longer interval. How many times do you need to repeat the experiment that water boils at 100 degrees celsius?
But if there is only one temperature record somewhere that shows positive feedback persistency, then where is the rebuttal: "Final and Unambigous Definite Concluding Evidence for AGW; Timbuktu weather data series Proves Positive feedback"? Of course this is an encouragement to go and study every usuable weather data series on persistency and be the big hero when finally able to provide conclusive proof. Anybody?
Now if you read my post completely, I wonder if you find any interlectual bankruptcy. That could be correct of course if you skip reading the italic paragraphs or let them drop out your memory as quickly as posible because they are bad news. This seems to happen often as can be seen here. It seems to be my own fault:
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....Recent research led by Dr. Norbert Schwarz, Ph.D., of the Institute for Social Research at the University of Michigan, Ann Arbor, confirmed this phenomenon. They found that presenting factual, accurate information that contradicts erroneous beliefs, and encouraging people to think about issues, not only often doesn’t help, it can actually reinforce the very myths being corrected! ...
...When the false claims are encountered again on a later occasion, all that is left may be the vague feeling that "I heard something like this before." This sense of familiarity, in turn, will foster the acceptance of statements as true.
...Mythbusters who fail to realize this natural trick our brains play on us, can fall into its trap. When debunking a myth, it’s common to first repeat it, but this technique can work against the quack buster. Simply repeating the myth may contribute to its later familiarity and acceptance. This Catch-22 predicament has been known for more than 60 years, since the research on wartime rumors by Allport and Lepkin. Still, the idea that false information needs to be confronted is so compelling that it’s still at the heart of most information campaigns, |
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| Yash |
| Posted: Mon Mar 03, 2008 9:55 am Post subject: |
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Forum Freshman
Joined: 03 Mar 2008
Posts: 76
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Green House Effect process is really simple to understand it goes like this --
Our earth absorbs heat radiation from sun, some of it is reflected back and rest of it is absorbed. Now, as we know that our atmosphere constitutes gases like Carbon dioxide, Methane, ozone. So these gases absorb the radiation reflected by earth, resulting in increase in temperature,this is known as green house effect. Therefore, more the increase in amount of these gases more the temp of the earth will increase.
So, You see it's too simple !!!!! |
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| andre |
| Posted: Sun Mar 09, 2008 6:23 am Post subject: |
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Forum Sophomore
Joined: 10 Aug 2007
Posts: 128
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I said:
| andre wrote: |
Hence (due to the lag) a positive feedback system tends to persist in a movement, opposing changes when the direction sign of the forcing function changes. This opposition delays the direction change or it even cancels the direction change when the forcing function changes direction back again before actual direction change of the system took place.
While a negative feedback (due to the lag) amplifies a change in direction of the forcing function, since it was already going that way, so it assists the change in direction, making it easier to happen even if the change of the forcing function was short in duration.
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Seeing the abundant reactions on this, perhaps a picture is worth a thousand words, so I made a most simple one dimensional random walk model here.
Click on the image to view it at its original size
The green graph represents the originan 'brownian motion' stepping randomly up or down with values between -0,5 and +0,5. For the red and brown graph a part of the former movement is added as positive feedback to the next step, for the blue graphs a part of the former movement is subtracted for the next step as a negative feedback.
We see two major differences between red and blue, blue resist changes while red "amplifies" them as expected for positive feedback. But we're not interested so much in that. It's the second effect what Karner is focussing upon. The red/brown graphs are much smoother than the original while the blue graphs have exagarated ripples or noise, the signal changes heading up or down much more often than the orginal green graph, while the red/brown ones only change direction occasionally.
My large number spreadsheet (400,000 itterations) shows that the -0.5 feedback signal changes direction up or down in ~64% of the steps while the +0.5% feedback nicely mirrors that, giving direction changes for only ~36% of the steps. For the +/- 0.75 factor feedback this is ~75% and ~25%. Even for +/- 0.1% the rate of heading changes is 52.5% versus 47.5%
So, taking any (detrended) signal, looking at the excursions from the normal value, one can count the heading changesversus maintaining the same direction at regular intervals to figure out if any feedback would be positive or negative. |
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