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Post by northsphinx on Jul 26, 2009 22:13:30 GMT
Temperature change = Forcing * Climate SensitivityIF the Forcing is in the range of 4wm-2 What range is the Climate sensitivity caalculated to?. 1, 10 or 100 wm-2? And most important, is it + or - before this number?
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Post by socold on Jul 27, 2009 0:20:21 GMT
Temperature change = Forcing * Climate SensitivityIF the Forcing is in the range of 4wm-2 What range is the Climate sensitivity caalculated to?. 1, 10 or 100 wm-2? And most important, is it + or - before this number? The climate sensitivity unit is degreesC/wm-2. Models put it at about 0.75, skeptics like Lindzen and Roy Spencer put it lower at something like 0.1 (my guess, I can't remember). As far as I know noone puts it at negative as that would imply additional energy into the system makes it colder.
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Post by sigurdur on Jul 27, 2009 0:34:08 GMT
IF the Forcing is in the range of 4wm-2 What range is the Climate sensitivity caalculated to?. 1, 10 or 100 wm-2? And most important, is it + or - before this number? The climate sensitivity unit is degreesC/wm-2. Models put it at about 0.75, skeptics like Lindzen and Roy Spencer put it lower at something like 0.1 (my guess, I can't remember). As far as I know noone puts it at negative as that would imply additional energy into the system makes it colder. And the models appear to have it totally to high, I also think Spencer has it too low. I just read a paper that indicated it to be .28 I will see if I can find the link again SoCold. The .7 is way out of bounds.
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Post by steve on Jul 27, 2009 8:47:32 GMT
The climate sensitivity unit is degreesC/wm-2. Models put it at about 0.75, skeptics like Lindzen and Roy Spencer put it lower at something like 0.1 (my guess, I can't remember). As far as I know noone puts it at negative as that would imply additional energy into the system makes it colder. And the models appear to have it totally to high, I also think Spencer has it too low. I just read a paper that indicated it to be .28 I will see if I can find the link again SoCold. The .7 is way out of bounds. So you are disagreeing with the PETM paper you linked to in the other thread.
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Post by northsphinx on Jul 27, 2009 12:47:38 GMT
Very disturbing with different definitions: en.wikipedia.org/wiki/Climate_sensitivity"equilibrium climate sensitivity refers to the equilibrium change in global mean near-surface air temperature that would result from a sustained doubling of the atmospheric (equivalent) CO2 concentration. This value is estimated, by the IPCC Fourth Assessment Report (AR4) as likely to be in the range 2 to 4.5°C with a best estimate of about 3°C" In degrees, BUT And from same source: "AR3 defined climate sensitivity alternatively in systematic units, equilibrium climate sensitivity refers to the equilibrium change in surface air temperature following a unit change in radiative forcing and is expressed in units of °C/(W/m2)" Further: en.wikipedia.org/wiki/Radiative_forcing" Radiative forcing can be used to estimate a subsequent change in equilibrium surface temperature ΔTs change arising from that radiative forcing via the equation ΔTs = λ x ΔF, where λ is the climate sensitivity, usually with units in K/(W/m2), and ΔF is the radiative forcing. A typical value of λ is 0.8 K/(W/m2), which gives a warming of 3K for doubling of CO2." In K/(W/m2) Lets use the older definition Socold ΔTs = λ x ΔF ΔF = Radiative forcing λ = climate sensitivity Regarding Radiative forcing See www.nap.edu/openbook.php?record_id=11175&page=R1Especially "Rethinking the Global Radiative Forcing Concept" on page 83 and forward. www.nap.edu/openbook.php?record_id=11175&page=83Radiative forcing itself is not unquestioned I quote above paper: "Although the traditional TOA radiative forcing concept remains very useful, it is limited in several ways. It is inadequate to describe fully the radiative effects of several anthropogenic influences..." I read is as what effect radiative forcing have on climate sensitivity. They ARE linked. CO2 do not have the possibility to have a radiative forcing impact IN the troposphere. The heat-flux by radiation in the atmosphere is driven by heat differences between absorbing and emitting molecules. CO2 is absorbing about 100% of "possible" radiation in about approx 10 m atmosphere. The heat difference in 10 m of the atmosphere is about 0. There is no heat difference and therefore not possible to have a heat flux driven by radiation between CO2 in these short distances in the atmosphere. And absolutely not for longer distances. The CO2 will be acting as 10 meter of insulation. From a radiation view from the earth surface. Between earth surface and the lowest part of the atmosphere is it another issue. If the earth is warmer than the atmosphere as under a sunny day is the CO2 trapping its part of the LW radiation spectrum in the first meters. It may be a small difference ONLY in sunny and calm conditions over land. Any wind will have a higher convection effect than CO2 will have. Basic heat transfer. During the night when the earth surface temperature drops will an increased CO2 level act as mirror for outgoing LW and resend half of it back to the surface which can emit it in all of the spectrum of a near BB so it can escape into cold space. And when the surface have a lower temperature than the atmosphere a few meters above, is the heat flux going down-wards before radiate direct into space within spectrum not absorbed by CO2 or vapor.
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Post by northsphinx on Jul 27, 2009 16:37:22 GMT
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Post by socold on Jul 27, 2009 18:24:10 GMT
Most concepts in science are questioned, because often they are only 99% correct. The concept of "species" as a classification of life for example is well accepted but still questioned due to certain exceptions.
Radiative forcing is a concept to compare how much different influences change the net energy gain/loss of the Earth.
Then if you also happen to know how the Earth reacts to gaining 1wm-2 extra energy, you can tell how it will react to various influences.
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Post by nautonnier on Aug 1, 2009 17:07:57 GMT
Lets take this a step at a time I model a building where I put a stack of kindling down against the wooden wall. Then set light to it. Keeping everything else static in the building my model shows it burns down in 1 hour. I then repeat the modeling with a different type of wall and again keeping everything else invariant find it takes 90 minutes to burn down. Thus the flammability can be compared. I am not in favor of using analogies as there are always differences. But in this case so far the kindling is analogous to the forcing. Whether the building burns down in 1 hour or sprinklers save it is analogous to the response. However that response doesn't alter the concept or value of the forcing which is the same irregardless of how the system responds to it. As soon as you try to calculate the effect you are calculating the response, not the forcingResponse is not part of the forcing. The forcing is equivalent to the kindling being put against the wall. Of course that doesn't take into account the response. It's not supposed to. The simple act of putting kindling next to the wall or increasing solar output by 2% or doubling co2 knock the system out of balance and the system will respond to get back into balance. Same with the climate models. There are instantaneous doubling experiments of course, but also experiments with gradual increases in co2 (like 1% a year). It makes little difference to the final state whether you gradually increase the forcing to doubled-level or instantly change it. Convection and hydrological effects are considered - in the response. Take the kindling again. Putting flaming kindling up against a wall doesn't take into account the response. Yet it's certainly not "totally unreal". It's the input into what the system is about the respond to. That's the response. Of course the response alters the forcing, otherwise how would the system return to energy balance? But that doesn't alter the intial forcing. A solar output increase of 2% creates a 4wm-2 radiative forcing, meaning that if the Earth is in energy balance and solar output increases 2%, 4wm-2 more energy will be aborbed by the Earth than emitted. In response the Earth warms up, convection alters until many years later the forcing relative to the start point is now 0wm-2. That however doesn't mean the forcing from a 2% solar output is zero. That's why the forcing doesn't take into account the response, it would be meaningless if it did. Sorry for the delay in response - but one has to earn a crust. I shall type this slowly for you SoCold so you understand what I am saying. "A solar output increase of 2% creates a 4wm-2 radiative forcing, meaning that if the Earth is in energy balance and solar output increases 2%, 4wm-2 more energy will be aborbed by the Earth than emitted. In response the Earth warms up, convection alters until many years later the forcing relative to the start point is now 0wm-2. That however doesn't mean the forcing from a 2% solar output is zero. That's why the forcing doesn't take into account the response, it would be meaningless if it did."Remember that the IPCC definition of the term RADIATIVE FORCING assumes an instantaneous addition of a 'green house gas' (sic) with a static troposphere and only considers the effect on absorption of long wave radiation of energy transiting the static troposphere from the surface to the tropopause. "A solar output increase of 2% creates a 4wm-2 radiative forcing, meaning that if the Earth is in energy balance and solar output increases 2%, 4wm-2 more energy will be aborbed by the Earth than emitted"But if the atmosphere is allowed to react (thus in reality rather than the hypothetical metric 'Radiative Forcing') there is almost immediate convection AND water vapor in the hydrologic cycle enhances this convection and carries heat as latent heat rapidly up to the tropopause. These are not small amounts and bypass the green house gas that is there. So the ACTUAL Forcing is made up of comparison of Radiation in with 'Radiative' and 'Convective' aspects out. In many cases the convective effects also significantly raise the albedo so actually act to PREVENT the input radiation usually in the tropics where such albedo rises are most effective. "In response the Earth warms up, convection alters until many years later the forcing relative to the start point is now 0wm-2""many years later" ?? You obviously know little about weather. It may not be obvious to a layman but storm cells can generate inside a few MINUTES let alone years many storm cells build and dissipate in less than an hour. As they dissipate they are replaced by new convective cells and these may build on the effect of each other. www.springerlink.com/content/l15t84020015wknj/Even in temperate zones a 'sea breeze' - inflow of air from the ocean as the hot land causes convective updrafts - will form and you will see cumulus building just inshore. In the tropics these become towering storm cells. So what REALLY happens is that the extra forcing within minutes will start convective processes that both increase albedo - reducing the input energy, and transport large quantities of heat to the tropopause. By definition Radiative Forcing which only measures absorption of radiation in the static troposphere, does not account for these processes. So is a hypothetical metric. The current GCMs like WRF and others, do not yet model these convective and cloud processes at all well. As I said before, the IPCC accepts that they have not modeled clouds and their effect on climate well. Perhaps the next iteration they expect to try. See: www.isac.cnr.it/~ipwg/meetings/beijing/pres/Poster-Chen.pdf<<SNIP>> "Moist convection remains one of the largest sources of uncertainty in GCM predictions of future climate change, because of the role of the diabatic heating profile in the large-scale circulation and precipitation anomalies, the stabilization of the boundary layer by downdrafts, the regulation of convection penetration depth by entrainment of dry air, and the effect of updraft strength on detrainment into anvil clouds. We are in the midst of development of the GISS Model E cumulus parameterization in preparation for IPCC AR5." <<SNIP>> Perhaps once the processes of convection, hydrologic cycle and albedo effects are better understood, the definition of radiative forcing could be changed to the effect on a REAL atmosphere not just radiation through a hypothetical unresponsive slab. If that were to be done then it could be experimentally measured and could become real physics.
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Post by sigurdur on Aug 1, 2009 17:40:29 GMT
Thank you. The above response was excellent!
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Post by icefisher on Aug 1, 2009 18:43:15 GMT
Thank you nautonnier. Your post really hits squarely on the overall issue.
big corporate green has to raise a lot of money constantly to keep their thing going. thus the truth is once they know anything at all about anthropogenic effects of CO2 emissions, good or bad, significant or insignificant, the cacophany of screams of foul fill the air. All they need to know is we are having an effect on the earth, a complete no brainer.
it reminds me of when at 16 I first got my drivers license. Me and two buds in the front seat and 3 girls in the back, I was going a little too fast on Sepulveda Blvd through the pass and hit a construction site on a tight turn. The tires were squealing through the turn and the gals in the backseat let out an ear shattering screech. On the other side of the turn everything was fine except my adrenaline rush. . . .and it was perfectly clear not much of that came from the tires squealing.
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Post by socold on Aug 1, 2009 20:05:47 GMT
"A solar output increase of 2% creates a 4wm-2 radiative forcing, meaning that if the Earth is in energy balance and solar output increases 2%, 4wm-2 more energy will be aborbed by the Earth than emitted"But if the atmosphere is allowed to react (thus in reality rather than the hypothetical metric 'Radiative Forcing') You mention the atmosphere will "react". The reaction is an effect of a cause. What cause? An energy inbalance. How do we quantify that inbalance - radiative forcing. You've dismissed radiative forcing, so have dismissed the metric for quantifying the cause. This is all response stuff. Radaitive forcing will never take into account the response because that would defeat the entire point of the concept. In fact if radiative forcing took into account the response it would always be zero. Double solar output? Radiative forcing = zero Quadruple solar output? Radiative forcing = zero Pointless.
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Post by icefisher on Aug 2, 2009 1:49:21 GMT
In fact if radiative forcing took into account the response it would always be zero. Double solar output? Radiative forcing = zero Quadruple solar output? Radiative forcing = zero Pointless. Not pointless at all Socold. Its nice weather outside today. Zero is a good place to be. I understand your concern about flying through space on this seemingly pilotless planet, but thats what faith is for Socold. Make God your pilot and you will be happy and probably live longer too.
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Post by radiant on Aug 2, 2009 5:20:40 GMT
In fact if radiative forcing took into account the response it would always be zero. Double solar output? Radiative forcing = zero Quadruple solar output? Radiative forcing = zero Pointless. I cant follow this. If you double the solar output the earth immediately begins with a radiation emmision insufficient to cool the earth and therefore it warms until the extra inwards heat is balanced by the extra outwards heat. After the warming there is no longer any further radiative forcing But if you double the solar radiation the earth is forced to warm up regardless of the response because the response can only be present via additional warming of the earth. Whatever you are saying you need to reword it surely?
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Post by poitsplace on Aug 2, 2009 8:50:48 GMT
They're just going back and forth talking about the amount of energy it takes to re-establish equilibrium after "CO2 forcing" (if it even has a significant impact). Most of it was a misunderstanding. Basically after equilibrium is established the energy in and out is once again balanced. This of course says nothing about the local conditions on say...the ground. Double the forcing from the sun and the ground will get incredibly hot...but a new equilibrium WILL be reached with just as much going out as is coming in. The real concept they're dancing around is how much of a temperature increase it takes to establish the new equilibrium. Skeptics and 'lukewarmers' point out that the vast majority of feedbacks fall between strongly negative and weakly positive. This means that whatever forcing (if any) CO2 causes...the new equilibrium should be established at about (or below) 1.5C higher temperatures for a doubling of CO2. Alarmists on the other hand seem to believe that the feedbacks are strongly positive and that it will take 2-3 times more warming to balance out CO2's forcing. The problem with this is that the proposed feedbacks would also be driven by the changes that they cause. Yes, this means that any such feedbacks should start driving themselves to the breaking point at the first sign of a change...and this is in fact the reason that such feedbacks are unusual in nature. en.wikipedia.org/wiki/Thermal_runaway
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Post by steve on Aug 2, 2009 9:39:25 GMT
nautonnier said:
No the forcing is the change in the energy input. The changes in the factors that are affected by any changes in convection are best represented as a response to the forcing because, obviously, they don't happen without the forcing and, possibly, they will happen in proportion to the forcing.
Eg. if the forcing is 1W and the temperature change is 2C then the response is "2C rise for each 1W forcing". That means if the forcing is 1.5W you can estimate that the warming will be 3C.
The error in this is the assumption that this "almost immediate" change in convection and water vapour is so important as to overcome the change in the forcing.
In reality, over time the extra heating is likely to be distributed through the atmosphere. Since convection is related to imbalances in the atmosphere, an increase in convection by the amounts suggested is not a given.
To "bypass" all these greenhouse gases, the convection has to rise above the layers where a lot of radiation escapes to space. But such convection would also lift water vapour up to these layers, so reducing the amount of radiation escaping to space (because water vapour is a greenhouse gas).
Additionally, an increase in convection and water vapour changes the clouds and levels of water vapour in the troposphere which also affect radiation balance.
(PS. to icefisher on previous page, a 2% increase in solar output results in an average 4.7W increase in solar irradiation at the earth's surface - similar to a doubling of CO2).
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