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Post by nautonnier on Mar 24, 2010 2:22:55 GMT
You are correct in stating that the hydrologic cycle is not modeled well, it is the largest uncertainty in the AGW feedbacks. Where did you find that the IPCC (which does not do research, but OK, that's something different) does not include convection, but only radiative transport? AJ Read the AR4 WG1 Summary report www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-human-and.htmlYou will find the only mention of clouds is in an albedo diagram (reflecting incoming radiation) you will find no mention of convection at all. Look at SoCold's favorite diagram If you read through the working group 1 report you will see that there is no mention of heat transport by convection. Where convection is mentioned it is usually in the assessment of feedback caused by radiative forcing due to water vapor. For example: "although modest RH decreases are noted at high levels on interannual time scales (Minschwaner and Dessler, 2004; Section 3.4.2.3). Seasonal variations in observed global LW radiation trapping are also consistent with a strong positive water vapour feedback (Inamdar and Ramanathan, 1998; Tsushima et al., 2005). Note, however, that humidity responses to variability or shorter timescale forcing must be interpreted cautiously, as they are not direct analogues to that from greenhouse gas increases, because of differences in patterns of warming and circulation changes."Pg 634 "They also found a model global temperature response similar to that observed, but not if the water vapour feedback was switched off (although the study neglected changes in cloud cover and potential heat uptake by the deep ocean). Using radiation calculations based on humidity observations, Forster and Collins (2004) found consistency in inferred water vapour feedback strength with an ensemble of coupled model integrations, although the latitude-height pattern of the observed humidity response did not closely match any single realisation. They deduced a water vapour feedback of 0.9 to 2.5 W m–2 °C–1, a range which covers that of models under greenhouse gas forcing (see Figure 8.14)."Pg 635 Finally they admit to 'modeling clouds being an uncertainty' : "8.6.3.2 Clouds By reflecting solar radiation back to space (the albedo effect of clouds) and by trapping infrared radiation emitted by the surface and the lower troposphere (the greenhouse effect of clouds), clouds exert two competing effects on the Earth’s radiation budget. These two effects are usually referred to as the SW and LW components of the cloud radiative forcing (CRF). The balance between these two components depends on many factors, including macrophysical and microphysical cloud properties. In the current climate, clouds exert a cooling effect on climate (the global mean CRF is negative). In response to global warming, the cooling effect of clouds on climate might be enhanced or weakened, thereby producing a radiative feedback to climate warming (Randall et al., 2006; NRC, 2003; Zhang, 2004; Stephens, 2005; Bony et al., 2006). In many climate models, details in the representation of clouds can substantially affect the model estimates of cloud feedback and climate sensitivity (e.g., Senior and Mitchell, 1993; Le Treut et al., 1994; Yao and Del Genio, 2002; Zhang, 2004; Stainforth et al., 2005; Yokohata et al., 2005). Moreover, the spread of climate sensitivity estimates among current models arises primarily from inter-model differences in cloud feedbacks (Colman, 2003a; Soden and Held, 2006; Webb et al., 2006; Section 8.6.2, Figure 8.14). Therefore, cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates. This section assesses the evolution since the TAR in the understanding of the physical processes involved in cloud feedbacks (see Section 8.6.3.2.1), in the interpretation of the range of cloud feedback estimates among current climate models (see Section 8.6.3.2.2) and in the evaluation of model cloud feedbacks using observations (see Section 8.6.3.2.3)." P 635 - 636 Note again that the clouds are only seen as a water vapor feedback to rising CO 2 that affects radiation- there is NO mention of convective heat transport.
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Post by steve on Mar 24, 2010 10:25:09 GMT
He didn't say that. He said that the radiation would originate from a higher layer on average, and that the higher layer is cooler so will radiate less. The temperature of the layer is still driven mainly by convection. He writes in 14.6: "If therefore the concentration c is doubled, the origin of the radiation moves up to a level where the pressure is less by a factor of 2 e-05- about 3 km higher - where, assuming a lapse rate of 6 C/km the temperature on average will be about 18 degrees less. I f we assume the temperature of of 250 K for the undisturbed case, it will be 232 K in the doublet CO2 case. With this temperature difference the drop in radiation emitted within the spectral intervals 700-750 cm e-1 will be about 3 W/m2" Satellite measurement show us very clear that about 220K for undisturbed is the case not as assumed 250 K. That is about stratopause. The coldest place. Top of convection. In the stratosphere is temperature increasing with about 50 K in 40 km or 1,25 C/km. 3 km higher is nearly 4 degrees warmer. Not 18 degrees cooler. If you reread that section, you will see that Houghton refers to radiation from the "wings" of the 15 micron peak. The point he makes is that a lot of this radiation originates from the troposphere, so the tropospheric lapse rate is relevant. As Houghton says further down, it is a crude estimate, and proper account of the detailed line structure is required. Presumably the further from the 15 micron peak into the "wings" the deeper into the troposphere you go (until you are overwhelmed by other causes of absorption that is). Nautonnier talks about "returning to basics". This area has been revisited a number of times. Where CO2 is involved a common citation is: Myhre et al., New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters, Vol 25, No. 14, pp 2715–2718, 1998 which calculates that doubling CO2 would reduce outgoing longwave from a typical atmosphere by 4W/m^2, which is supportive of Houghton's estimates and explanation.
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Post by steve on Mar 24, 2010 10:42:43 GMT
Nautonnier,
It is obvious that any climate or forecast model is dependent on representing convection, and the heat that is transported by convection, and there are many such references in the IPCC report, for example to the change in lapse rate or the flow of heat from the tropics to the higher latitudes etc etc etc etc etc. It seems that your chosen search phrase "heat transport by convection" is inappropriate.
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Post by nautonnier on Mar 24, 2010 10:49:39 GMT
He writes in 14.6: "If therefore the concentration c is doubled, the origin of the radiation moves up to a level where the pressure is less by a factor of 2 e-05- about 3 km higher - where, assuming a lapse rate of 6 C/km the temperature on average will be about 18 degrees less. I f we assume the temperature of of 250 K for the undisturbed case, it will be 232 K in the doublet CO2 case. With this temperature difference the drop in radiation emitted within the spectral intervals 700-750 cm e-1 will be about 3 W/m2" Satellite measurement show us very clear that about 220K for undisturbed is the case not as assumed 250 K. That is about stratopause. The coldest place. Top of convection. In the stratosphere is temperature increasing with about 50 K in 40 km or 1,25 C/km. 3 km higher is nearly 4 degrees warmer. Not 18 degrees cooler. If you reread that section, you will see that Houghton refers to radiation from the "wings" of the 15 micron peak. The point he makes is that a lot of this radiation originates from the troposphere, so the tropospheric lapse rate is relevant. As Houghton says further down, it is a crude estimate, and proper account of the detailed line structure is required. Presumably the further from the 15 micron peak into the "wings" the deeper into the troposphere you go (until you are overwhelmed by other causes of absorption that is). Nautonnier talks about "returning to basics". This area has been revisited a number of times. Where CO2 is involved a common citation is: Myhre et al., New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters, Vol 25, No. 14, pp 2715–2718, 1998 which calculates that doubling CO2 would reduce outgoing longwave from a typical atmosphere by 4W/m^2, which is supportive of Houghton's estimates and explanation. "which calculates that doubling CO2 would reduce outgoing longwave from a typical atmosphere by 4W/m^2,"As with all these statements one has to read them and understand the caveats that they contain. The output is calculated not measured the observations from ERBE appear to show that the calculation is incorrect. Doubling CO 2 is not feasible as there is probably insufficient fossil fuel reserves to do this - and the output would need to be fast to beat Henry's Law Typical Atmosphere is a very loose definition. The IPCC AR4 WG1 report in several places says that the observations of the atmosphere are not good enough to assess models. The IPCC uses a 'slab' typical atmosphere in which all convection is stopped and of course there is the ICAN atmosphere but that is just a mathematical simplification again with no convection. But given those caveats you have a nice mathematical unproven postulate.
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Post by northsphinx on Mar 24, 2010 12:24:16 GMT
In fact Steve is he writing: "Reference again to figure 12.7 shows that it is radiation from the wings of the 15 micron carbon dioxide band that originates from the troposphere."
That is the largest part of CO2 band radiation is NOT from originated from the troposphere but from, as he state in other chapter, the stratosphere. Where increased CO2 cool the earth.
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Post by steve on Mar 24, 2010 12:57:35 GMT
In fact Steve is he writing: "Reference again to figure 12.7 shows that it is radiation from the wings of the 15 micron carbon dioxide band that originates from the troposphere." That is the largest part of CO2 band radiation is NOT from originated from the troposphere but from, as he state in other chapter, the stratosphere. Where increased CO2 cool the earth. It is fully a part of the greenhouse theory, and has been for decades, that increased CO2 will cool the stratosphere and warm the troposphere. Stratospheric cooling was a prediction of the theory, following which stratospheric cooling was observed. You would need to show that the cooling influence in the stratosphere overcomes the warming influence in the troposphere. Current calculations show that it does not.
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Post by steve on Mar 24, 2010 13:15:19 GMT
Nautonnier,
These are all just the usual irrelevant diversions indicating that you are not interested in looking for a middle ground where things can be agreed as reasonable.
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Post by northsphinx on Mar 24, 2010 14:24:11 GMT
Where CO2 is involved a common citation is: Myhre et al., New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters, Vol 25, No. 14, pp 2715–2718, 1998 which calculates that doubling CO2 would reduce outgoing longwave from a typical atmosphere by 4W/m^2, which is supportive of Houghton's estimates and explanation. Here is the link to Myhre et al. folk.uio.no/gunnarmy/paper/myhre_grl98.pdf I cant find the famous 4W/m^2 statement there. by the way What is Your opinion on this paper www.cgd.ucar.edu/cms/wcollins/papers/rtmip.pdf
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Post by steve on Mar 24, 2010 15:15:19 GMT
Where CO2 is involved a common citation is: Myhre et al., New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters, Vol 25, No. 14, pp 2715–2718, 1998 which calculates that doubling CO2 would reduce outgoing longwave from a typical atmosphere by 4W/m^2, which is supportive of Houghton's estimates and explanation. Here is the link to Myhre et al. folk.uio.no/gunnarmy/paper/myhre_grl98.pdf I cant find the famous 4W/m^2 statement there. by the way What is Your opinion on this paper www.cgd.ucar.edu/cms/wcollins/papers/rtmip.pdfIn the Myhre paper, the forcing from CO2 is given in Table 3 as 5.35 x log(Ccurrent/Corig). For a doubling, it gives 3.7W/m^2, not 4W/m^2. I rounded to the nearest integer. The Collins paper is essentially looking at the forcings as calculated in a large number of climate models. It says that not all models calculate the forcings to be the same (ie. it is saying that some of them must be wrong), so that it would be better if the models provided the forcings as a model output. so the key results of an individual model (eg. its sensitivity) can be better understood. I understand that will happen for AR5.
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Post by northsphinx on Mar 24, 2010 16:14:16 GMT
I see Steve. I was so focused on this 4. It is always nice to put things in perspective. Theoretical Wing AGW heating during average clear sky conditions Compare with real measurements: Natural variations is multiple larger than even the small but still overestimated theoretically impact of the CO2 wings. Overestimated due to theoretically clear sky and dry conditions. Increased heat flux may not be increase temperature, it can also be increase vapor and more chilling clouds. Or even less clouds and more outgoing radiation. Africa's rain forests and deserts is a very speaking example of difference in outgoing radiation most due to clouds. It is all about the clouds.
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Post by aj1983 on Mar 24, 2010 16:36:58 GMT
Convection is parametrized in climate models, but I don't think they are explicitly calculated (I should ask or look that up). That would require a very high spatial and time resolution. Average fluxes can be calculated (approximated) however over a larger area and time (that's something different than an unresponsive slab...). I think we all agree however that the cloud/aerosol feedbacks are least understood. They might have a strong negative feedback, but the general idea is that it will probably only be a slight negative feedback. This is represented well by the direct aerosol forcing and cloud albedo effect, which can, inside the error bars given theoretically almost counteract global warming from greenhouse gasses (the ongoing "climate sensitivity" discussion). (It is interesting to note that possible cooling feedbacks are much poorly understood than the warming feedbacks.) However, the climate sensitivity can be determined by many independent measures, and has shown to be rather large (but also with a fairly large range), which is not surprizing considering the considerable temperature variations in the earth's history. for a discussion see www.skepticalscience.com/climate-sensitivity.htm
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Post by nautonnier on Mar 24, 2010 17:05:52 GMT
Nautonnier, These are all just the usual irrelevant diversions indicating that you are not interested in looking for a middle ground where things can be agreed as reasonable. "These are all just the usual irrelevant diversions indicating that you are not interested in looking for a middle ground where things can be agreed as reasonable."This is a revealing statement Steve. If you deal in validation and verification - there is no negotiated compromise result. Science is not carrying out some reasonable kind of negotiation it is about trying to find the truth. I'll swap you my agreement on Einstein's relativity theory on the speed of light, for your agreement on Modified Newtonian Dynamics. you have 11 dimensions in string theory and I make it 15 - tell you what - split the difference and let's agree on 13..... The AGW definitions live in a hypothetical world yes this gives you hypothetical constructs that you can compare with other hypothetical constructs generated in the same hypothetical world. I am quite prepared to accept that. It is the transference of those constructs into the real world from the imaginary that causes problems. I shall try an analogy - I have a thin wooden plank SeeSaw and it currently has a bucket on each end the less full one is in the air and the more full one on the ground. The buckets are filled a cup of liquid at a time I could say - hypothetically - if I was to instantaneously double the weight of this higher bucket by filling it - and assuming the seesaw does not move then this thin wooden plank would break Given the hypothetical constraints this may be true You could use the hypothetical construct to find out how much of different liquid densities you would need to break the seesaw hypothetically In the real world however, as you start to fill the higher bucket the seesaw will move and the heavier bucket would reach the ground and the plank would not break It is also possible that the bucket cannot be doubled in weight by filling it as it is already almost full but this is the real world
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Post by steve on Mar 24, 2010 18:00:09 GMT
More diversions.
I do not demand that we agree. I suggest that we *try* to find areas of agreement and not bring in unconstructive distractions that could be addressed in other threads.
This is not the first time that the concept of radiative forcing has started out with either a misconception as to what it is, or a claim that it has been calculated wrongly, or a suggestion that it could not possibly be considered in isolation, and ended up with a general complaint about how could a mere 3-4W/m^2 make a difference when there is so much else going on.
Suppose one were to argue that a 1% increase in the solar constant would make no difference to the climate. Well surely it's only 1% and tiny compared with variations in the earth's outgoing LW. Hasn't the climate been stable despite a 5-10% increase in TSI over billions of years? OK, what about 2% or 3%...?
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Post by northsphinx on Mar 24, 2010 18:16:18 GMT
Cant resist to mention another great document ams.allenpress.com/archive/1520-0477/90/3/pdf/i1520-0477-90-3-311.pdfCompare the uncertainties with claimed CO2 forcing of 3.7 W m-2. Example "They estimate, based on comparisons with ERBE, limited CERES, and some surface data, that the errors are of the order of 5–10 W m−2 at TOA and 10–15 W m-2 at the surface"
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Post by steve on Mar 24, 2010 18:39:00 GMT
Northsphinx, errors due to sampling or instrument error don't affect the net change that would occur if you doubled CO2. Just because I don't know how rich Warren Buffet is doesn't mean I'm wrong if I give him $10 and then claim he is $10 richer.
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