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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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What is the net feedback from clouds?

What the science says...

Select a level... Basic Intermediate

Evidence is building that net cloud feedback is likely positive and unlikely to be strongly negative.

Climate Myth...

Clouds provide negative feedback

"Climate models used by the International Panel on Climate Change (IPCC) assume that clouds provide a large positive feedback, greatly amplifying the small warming effect of increasing CO2 content in air. Clouds have made fools of climate modelers. A detailed analysis of cloud behavior from satellite data by Dr. Roy Spencer of the University of Alabama in Huntsville shows that clouds actually provide a strong negative feedback, the opposite of that assumed by the climate modelers. The modelers confused cause and effect, thereby getting the feedback in the wrong direction." (Ken Gregory)

At a glance

What part do clouds play in your life? You might not think about that consciously, but without clouds, Earth's land masses would all be lifeless deserts. Fortunately, the laws of physics prevent such things from being the case. Clouds play that vital role of transporting water from the oceans to land. And there's plenty of them: NASA estimates that around two-thirds of the planet has cloud cover.

Clouds form when water vapour condenses and coalesces around tiny particles called aerosols. Aerosols come in many forms: common examples include dust, smoke and sulphuric acid. At low altitudes, clouds consist of minute water droplets, but high clouds form from ice crystals. Low and high clouds have different roles in regulating Earth's climate. How?

If you've ever been in the position to look down upon low cloud-tops, perhaps from a plane or a mountain-top, you'll have noticed they are a brilliant white. That whiteness is sunlight being reflected off them. In being reflected, that sunlight cannot reach Earth's surface - which is why the temperature falls when clouds roll in to replace blue skies. Under a continuous low cloud-deck, only around 30-60% of the sunlight is getting through. Low clouds literally provide a sunshade.

Not all clouds are such good sunshades. Wispy high clouds are poor reflectors of sunlight but they are very effective traps for heat coming up from below, so their net effect is to aid and abet global warming.

Cloud formation processes often take place on a localised scale. That means their detailed study involves much higher-resolution modelling than the larger-scale global climate models. Fourteen years on, since Ken Gregory of the dubiously-named Big Oil part-funded Canadian group, 'Friends of Science', opined on the matter (see myth box), big advances have been made in such modelling. Today, we far better understand the net effects of clouds in Earth's changing climate system. Confidence is now growing that changes to clouds are likely to amplify, rather than offset, human-caused global warming in the future.

Two important processes have been detected through observation and simulation of cloud behaviour in a warming world. Firstly, just like wildlife, low clouds are migrating polewards as the planet heats up. Why is that bad news? Because the subtropical and tropical regions receive the lion's share of sunshine on Earth. So less cloud in these areas means a lot more energy getting through to the surface. Secondly, we are detecting an increase in the height of the highest cloud-tops at all latitudes. That maintains their efficiency at trapping the heat coming up from below.

There's another effect we need to consider too. Our aerosol emissions have gone up massively since pre-Industrial times. This has caused cloud droplets to become both smaller and more numerous, making them even better reflectors of sunlight. Aerosols released by human activities have therefore had a cooling effect, acting as a counter-balance to a significant portion of the warming caused by greenhouse gas emissions.

But industrial aerosols are also pollutants that adversely affect human health. Having realised this, we are reducing such emissions. That in turn is lowering the reflectivity of low cloud-tops, reducing their cooling effect and therefore amplifying global warming due to rising levels of greenhouse gases.

It sometimes feels as if we are between a rock and a hard place. We'd have been better off not treating our atmosphere as a dustbin to begin with. But there's still a way to fix this and that is by reducing all emissions.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

The IPCC's Sixth Assessment Report eloquently sums up where we are in our understanding of how clouds will affect us in a changing climate:

"One of the biggest challenges in climate science has been to predict how clouds will change in a warming world and whether those changes will amplify or partially offset the warming caused by increasing concentrations of greenhouse gases and other human activities. Scientists have made significant progress over the past decade and are now more confident that changes in clouds will amplify, rather than offset, global warming in the future."

The mistake made by our myth-provider, writing in 2009, was to leap to a conclusion without the information needed in order to do so. He is suggesting that clouds are inadequately represented in climate models, so they must have a negative effect on temperatures. Instead of making such leaps of faith, however, the specialists in cloud behaviour have recognised the challenges and met them square-on. We now know a lot more about clouds as a result.

In the at-a-glance section, we explain the important difference between high clouds and low clouds, agents of warming and cooling respectively. Careful examination of older satellite records has detected large-scale patterns of cloud change between the 1980s and 2000s (Norris et al. 2016). Observed and simulated cloud change patterns are consistent with the poleward retreat of midlatitude storm tracks, the expansion of subtropical dry zones and increasing height of the highest cloud tops at all latitudes. The main drivers of these cloud changes appear to be twofold: increasing greenhouse gas concentrations and recovery from volcanic radiative cooling. As a result, the cloud changes most consistently predicted by global climate models have indeed been occurring in nature.

With respect to the cooling low clouds, one particularly important area of study has involved marine stratocumulus cloud-decks. These are extensive, low-lying clouds with tops mostly below 2 km (7,000 ft) altitude and they are the most common cloud type on Earth. Over the oceans, stratocumulus often forms nearly unbroken decks, extending over thousands of square kilometres. Such clouds cover about 20% of the tropical oceans between 30°S and 30°N and they are especially common off the western coasts of North and South America and Africa (fig.1). That's because the surface waters of the oceans are pushed away from the western margins of continents due to the eastwards direction of Earth's spin on its axis. Taking the place of these displaced surface waters are upwelling, relatively cool waters from the ocean depths. The cool waters serve to chill the moist air above, making its water vapour content condense out into cloud-forming droplets.

 Satellite image of stratocumulus clouds.

Fig. 1: visible satellite image of part of an extensive marine stratocumulus deck off the western seaboard of North America, with Baja California easily recognisable on the right. Image: NASA.

With their highly reflective tops that block a lot of the incoming sunlight, the marine stratocumulus clouds have a very important role as climate regulators. It has long been known that increasing the area of the oceans covered by such clouds, even by just a few percent, can lead to substantial global cooling. Conversely, decreasing the area they cover can lead to substantial global warming.

Although many cloud-types are produced by convection, driven by the heated land or ocean surface, marine stratocumulus clouds are different. They are formed and maintained by turbulent overturning circulations, driven by radiative cooling at the cloud tops. It works as follows: cold air sinks, so that radiatively-cooled air makes its way down to the sea surface, picks up moisture and then brings that moisture back up, nourishing and sustaining the clouds.

Stratocumulus decks can and do break up, though. This happens when that radiative cooling at the cloud tops becomes too weak to send colder air sinking down to the surface. It can also occur when the turbulence that can entrain dry and warm air, from above the clouds into the cloud layer, becomes too strong.

The importance of such processes has been further investigated recently, using an ultra-high resolution model with a 50-metre grid size. (Schneider et al. 2019). Global climate models typically have grid sizes of tens of kilometres. At that resolution, they cannot detail such fine-scale processes. This model, by contrast, is able to resolve the individual stratocumulus updraughts and downdraughts.

 Results of modelling of marine stratocumulus behaviour.

Fig. 2: results of modelling of marine stratocumulus behaviour in a high-CO2 world. This one compares conditions at 400 ppm (present) and 1600 ppm (hopefully never, but relevant to the Palaeocene and Eocene when a super-Hothouse climate prevailed). Redrawn from Schneider et al. 2019.

The modelling shows how oceanic stratocumulus decks become unstable and break up into scattered cumulus clouds. That occurs at greenhouse gas levels of around 1,200 ppm (fig. 2). When that happens, the ocean surface below the clouds warms abruptly because the cloud shading is so diminished. In the model, the extra solar energy absorbed as stratocumulus decks break up, over an area estimated to cover about 6.5% of the globe, is enough to cause a further ~8oC of global warming. After the stratocumulus decks have broken up, they only re-form once CO2 levels have dropped substantially below the level at which the instability first occurred.

These results point to the possibility that there is a previously undiscovered, potentially strong and nonlinear feedback, lurking within the climate system. These findings may well help to solve certain palaeoclimatic problems, such as the super-Hothouse climate of the Palaeocene-Eocene, some 50 million years ago. It's been hard to fully explain that event, given that estimates of CO2 levels at the time do not exceed 2,000 ppm. Present climate models do not reach that level of warmth with that amount of CO2. But the fossil record presents hard evidence for near-tropical conditions in which crocodilians thrived - in the Arctic. Something brought about that climate shift!

The quantitative aspects of stratocumulus cloud-deck instability remain under investigation. However the phenomenon appears to be robust for the physical reasons described by Schneider and co-authors. Closer to the present, the recent acceleration of global warming may be partly due to a decrease in aerosols. Aerosols produce smaller and more numerous cloud droplets. These have the effect of increasing the reflectivity and hence albedo of low cloud-tops (fig. 3). It follows that if aerosol levels decrease, the reverse will be the case. Of considerable relevance here are the limits on the sulphur content of ship fuels, imposed by the International Maritime Organization in early 2015. These regulations were further tightened in 2020. An ongoing fall in aerosol pollution, right under the marine stratocumulus decks, would be expected to occur. As a consequence, the size and amount of cloud droplets would change, cloud top albedo would decrease and there would be increased absorption of solar energy by Earth. That would be on top of the existing greenhouse gas-caused global warming. James Hansen discussed this in a recent communication (PDF) here.

Cloud effects on Earth's radiation.

Fig. 3: NASA graphic depicting the relationship between clouds, incoming Solar radiation and long-wave Infrared (IR) radiation. High clouds composed of ice crystals reflect little sunlight but absorb and emit a significant amount of IR. Conversely low clouds, composed of water droplets, reflect a great deal of sunlight and also absorb and emit IR. Any mechanism that reduces low cloud-top albedo will therefore increase the sunlight reaching the surface, causing additional warming.

In their Sixth Assessment Report, the IPCC also points out that the concentration of aerosols in the atmosphere has markedly increased since the pre-industrial era. As a consequence, clouds now reflect more incoming Solar energy than before industrial times. In other words, aerosols released by human activities have had a cooling effect. That cooling effect has countered a lot of the warming caused by increases in greenhouse gas emissions over the last century. Nevertheless, they also state that this counter-effect is expected to diminish in the future. As air pollution controls are adopted worldwide, there will be a reduction in the amount of aerosols released into the atmosphere. Therefore, cloud-top albedo is expected to diminish. Hansen merely suggests this albedo-reduction may already be underway.

Last updated on 15 October 2023 by John Mason. View Archives

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Additional viewing

To explore this complex topic further, this is a great TED talk by climate scientist Kate Marvel:

Denial101x video(s)

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

Additional video from the MOOC

Expert interview with Steve Sherwood

Comments

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Comments 1 to 25 out of 74:

  1. FYI, the full Clement paper can be read here .
  2. It was suggested I move this discussion to this thread. The numbers show that clouds reflect more energy away then they trap. Given that the albedo has not been decreasing, and if anything has even increased slightly, this is completely inconsistent with clouds operating as a net positive feedback. Here are the numbers on how much incrementally more clouds reflect, according to Trenberth et al 2009: Clouds cover about 2/3rds of the surface, so 341 W/m^2 x 0.67 = 228 W/m^2 average incident on the clouds. 79 W/m^2 divided by 228 W/m^2 = 0.34 average reflectivity of clouds. 1/3rd of the surface is cloudless, so 341 W/m^2 x 0.33 = 113 W/m^2 average incident on the cloudless surface. 23 W/m^2 divided by 113 W/m^2 = 0.20 average reflectivity of the cloudless surface. 0.34 - 0.20 = 0.14. 341 W/m^2 x 0.14 = 48 W/m^2 loss for each additional m^2 of cloud cover. Here are the numbers on how much incrementally more clouds trap: The cloudy sky has a transmittance of 30 W/m^2, and the surface emitted through the cloudy sky is about 265 W/m^2 (396 x 0.67 = 265). 265 W/m^2 - 30 W/m^2 = 235 W/m^2 absorbed by the cloudy sky. The clear sky has a transmittance of 40 W/m^2, and the surface emitted through the clear sky is 131 W/m^2 (396 x 0.33 = 131). 131 W/m^2 - 40 W/m^2 = 91 W/m^2 absorbed by the clear sky. 91 W/m^2 divided by 131 W/m^2 = 0.69; 235 W/m^2 divided by 265 W/m^2 = 0.89. 0.89 - 0.69 = 0.20 difference between the cloudy and clear sky. 0.20 x 396 W/m^2 = 79 W/m^2 additional absorbed for each additional m^2 of cloud cover. If we assume that roughly half of the absorption and re-emission is back toward the surface (Trenberth actually has this being less than half), that comes to about 39 W/m^2, or about 10 W/m^2 less than the 48 W/m^2 reflected away. *If anyone doubts my calculations, I have backed check them by assuming that if half of the absorption is directed up out to space, then the weighted average totals should correspond to a temperature of about 255K. 0.69/2 (absorbed clear sky) + 0.31 passing through the clear sky = 0.66 and 0.89/2 (absorbed cloudy sky) + 0.11 passing through the cloudy sky = 0.55; 0.66 x 0.33 (clear sky) = 0.22 and 0.55 x 0.67 (cloudy sky) = 0.37; 0.22 + 0.37 = 0.59 emitted to space from the surface; 396 W/m^2 x 0.59 = 234 W/m^2 (about 254K), which is pretty close. *The missing 5 W/m^2 is probably due to Trenberth having greater than 50% of the atmospheric absorption being emitted up out to space.
  3. These calculations are consistent with general observations - that is cloudy days are usually cooler than sunny days. The opposite would be the case if clouds blocked more energy than they reflect away (cloudy days would be warmer than sunny days). It's true that at night the net effect of clouds tends to warm or slow heat loss, but these calculations are for global averages, so the differences between night and day are already factored in. The only exception to this would be in areas that are permanently snow or ice covered, as I think the reflectivity of clouds is roughly the same as snow and ice, so in these areas the presence of clouds tend to warm by blocking what little surface emitted energy there is.
  4. 2, 3, RW1, I suggest that you read the post here before commenting further. In particular, you'll find that this statement of yours is false:
    The numbers show that clouds reflect more energy away then they trap.
  5. The main point I'm getting at here is if the albedo is NOT decreasing (or has even slightly increased) and if incrementally more clouds don't trap more energy than they reflect away, where is the energy coming from that is supposed to be causing the enhanced warming? Also - if, as the AGW theory claims, an additional 3.7 W/m^2 at the surface is to become 16.6 W/m^2 largely through positive cloud feedbacks, then why doesn't it take more like 1075 W/m^2 at the surface to offset the 239 W/m^2 coming in from the Sun (16.6/3.7 = 4.5; 239 x 4.5 = 1075)?? The measured response of the system at the surface to incident energy is only about 1.6 (390 W/m^2/239 W/m^2 = 1.6). Since the atmosphere can't create any energy of its own, COE dictates the remaining difference of about 10.6 W/m^2 (3.7 x 1.6 = 6 W/m^2; 16.6 - 6 = 10.6 W/m^2) can only come from a reduced albedo (i.e. the Sun). So again, where is all the energy coming from that is supposed to be causing the enhanced warming?
  6. RW1,
    ...if the albedo is NOT decreasing (or has even slightly increased)
    Citation please. Otherwise either case is speculation. Albedo changes due to ice cover change will be measurable and predictable (in extent and effect, if not rate of arrival). Albedo changes due to cloud cover changes to my knowledge are uncertain at best. We'd know more if certain satellites (DSCVR) hadn't been mothballed, or others lost at launch, or unbuilt satellites had been built, but barring all that... all you have is speculation. Your assumption, however, that clouds must increase albedo is false. Again, read the above post, and other material. Clouds at high altitudes, which are expected to increase with warming, are composed of ice rather than water. These clouds are virtually transparent to visible light and so do not change the earth's albedo. They do, however, absorb in the infrared and so (as does all H2O) act as powerful greenhouse gases (even though they're solid, not gaseous). Similarly, lower (non-ice) clouds at night will trap heat without changing the albedo at all, so timing of development/dissipation is a factor. Along those same lines, clouds in winter (when the angle of incidence is already low, and the surface being shielded by the clouds is likely snow covered) will have no net change (or even a positive change!) in albedo, while still exhibiting GHG effects. So the assumption that clouds will increase albedo is based on an oversimplification which requires considerably more thought, research and observation.
    ...is to become 16.6 W/m^2 largely through positive cloud feedbacks...
    Citation, please. I don't know why you say this. If by 3.7 W/m2 you mean the effect of doubling CO2, then with a climate sensitivity of 3˚C (which is the current best estimate), that would translate into 3.7*3 = 11.1 W/m2, not 16.6 W/m2.
    ...then why doesn't it take more like 1075 W/m^2 ...
    Your equations are wrong. You are comparing the wrong factors. The equilibrium temperature of a body is that at which it emits the same amount as is being absorbed. Basically, the equilibrium temperature of the earth would be that at which it emits the same amount of energy as absorbed (i.e. absorbs 239 W/m2, then emits 239 W/m2). If CO2 adds the equivalent of 3.7 W/m2, then the total amount absorbed by the climate system becomes 239 W/m2 + 3.7 W/m2 = 242.7 W/m2. With expected feedbacks, this would be 239 W/m2 + 11.1 W/m2 = 250.1 W/m2. The question is, what surface temperature (actually, combined ocean/surface/atmospheric temperatures) results in this amount of emission (radiation)? The answer is a total of 3˚C. ...where is all the energy coming from that is supposed to be causing the enhanced warming? Outside of the above discussion, I think a major mistake that you may be making (this is a guess) is to equate water vapor feedback with clouds. While increased water vapor could result in more clouds, this is not necessarily the case, and clouds are not the form in which the main feedback would occur. Increased temperatures would increase the specific humidity... the amount of moisture carried in the air not in the form of clouds (condensation). This would be a proportional increase for every cubic meter of atmosphere, and H2O is a very powerful greenhouse gas. This would be the main contributor -- water vapor -- to positive feedbacks. Other positive feedbacks would include clouds (of different sorts), reduced snow and ice, natural release of CO2 and CH4, as well as others. All total, these would result in 3˚C of warming per doubling of CO2.
  7. Sphaerica (RE: 6), "Citation please" The albedo effect and global warming "Your assumption, however, that clouds must increase albedo is false. Again, read the above post, and other material. Clouds at high altitudes, which are expected to increase with warming, are composed of ice rather than water. These clouds are virtually transparent to visible light and so do not change the earth's albedo. They do, however, absorb in the infrared and so (as does all H2O) act as powerful greenhouse gases (even though they're solid, not gaseous). Similarly, lower (non-ice) clouds at night will trap heat without changing the albedo at all, so timing of development/dissipation is a factor. Along those same lines, clouds in winter (when the angle of incidence is already low, and the surface being shielded by the clouds is likely snow covered) will have no net change (or even a positive change!) in albedo, while still exhibiting GHG effects. So the assumption that clouds will increase albedo is based on an oversimplification which requires considerably more thought, research and observation." My assumption is not that clouds must increase albedo. The point is if clouds operate as a net positive feedback as claimed, and the data doesn't conclusively show that on average they trap more energy than reflect away, the only way clouds could operate as a net positive feedback is through a reduced albedo, which hasn't happened. I am also aware of the various types of clouds and the complexities of each as it relates to potential changes in the energy balance. " ...is to become 16.6 W/m^2 largely through positive cloud feedbacks... Citation, please. I don't know why you say this. If by 3.7 W/m2 you mean the effect of doubling CO2, then with a climate sensitivity of 3˚C (which is the current best estimate), that would translate into 3.7*3 = 11.1 W/m2, not 16.6 W/m2." It takes +16.6 W/m^2 at the surface for a 3 temperature rise. The 3.7 W/m^2 from 2xCO2 is the additional incident energy at the surface. This is then subject to the system gain or system amplification, which is a factor of about 1.6 (390 W/m^2/239 W/m^2). 3.7 W/m^2 x 1.6 = 6 W/m^2, which BTW, is how they are coming up with a 1 C intrinsic rise from 2xCO2, because +6 W/m^2 = +1C from the Stefan-Boltzman law. "...then why doesn't it take more like 1075 W/m^2 ... Your equations are wrong. You are comparing the wrong factors. The equilibrium temperature of a body is that at which it emits the same amount as is being absorbed. Basically, the equilibrium temperature of the earth would be that at which it emits the same amount of energy as absorbed (i.e. absorbs 239 W/m2, then emits 239 W/m2)." I'm aware of this. In simple energy balance terms, it takes about 390 W/m^2 at the surface to allow 239 W/m^2 to leave the system, offsetting the 239 W/m^2 coming in from the Sun. This is the system measured amplification factor of only about 1.6 to surface incident energy. The AGW claim of a 3 rise requires an amplification factor of 4.5 to allow and additional 3.7 W/m^2 incident on the surface to leave the system to restore equilibrium (239 W/m^2 in and out). In short, if it is going to take an additional 16.6 W/m^2 to allow 3.7 W/m^2 to leave the system to restore equilibrium, then why doesn't it take 1075 W/m^2 at the surface to allow the 239 W/m^2 from the Sun to leave the system at initial equilibrium (16.6/3.7 = 4.5; 1075/239 = 4.5)???
  8. Sphaerica (RE: 6), When there is a radiative imbalance, i.e. from additional CO2 added to the atmosphere which redirects more outgoing surface radiation back toward the surface, there is reduction in the amount of LW radiation leaving at the top of the atmosphere (more radiation is arriving from the Sun than is leaving at the top of the atmosphere). To achieve equilibrium, the system warms up until it again radiates the same amount of energy as is arriving from the Sun. To give a numerical example, there is about 239 W/m^2 arriving post albedo from the Sun and 239 W/m^2 leaving at the top of the atmosphere. This represents the system in equilibrium (energy in = energy out). If there was a radiative imbalance (or 'radiative forcing') of say 3.7 W/m^2 from a doubling of CO2, the energy leaving at the top of the atmosphere would reduce by 3.7 W/m^2 to 235.3 W/m^2. Currently, there is about 390 W/m^2 emitted by the surface. In this example, an additional 3.7 W/m^2 is received by the surface for a total of 393.7 W/m^2. The +3.7 W/m^2 is responded to the same as the 239 W/m^2 arriving from the Sun and will be amplified by a factor of about 1.6 (390/240 = 1.6), as this is the measurement of the surface response to incident energy. 3.7 W/m^2 x 1.6 = 6 W/m^2 to allow an additional 3.7 W/m^2 to leave the system to restore equilibrium (239 W/m^2 in and out). The new surface emitted radiation would be 396 W/m^2 (390 W/m^2 + 6 W/m^2), which corresponds to about a 1 C rise in temperature. Does this explain it better?
  9. 7, RW1,
    ...the data doesn't conclusively show that on average they trap more energy than reflect away...
    What data? Again, citation please. Although, I'd point out that as with everything, the climate has barely begun to reflect the changes. We haven't come close to doubling CO2 yet, and we've only seen half of the 1.4˚C of warming to which we've already committed. So the data isn't very likely to conclusively show anything, but that hardly makes it an argument that something is wrong.
    It takes +16.6 W/m^2 at the surface for a 3 temperature rise.
    Where are you taking this from?
    ...the system gain or system amplification...
    You're an electrical engineer.
    ...which is a factor of about 1.6 (390 W/m^2/239 W/m^2)
    Again, where are you getting this math from? Do you have a source, or is it your own inference?
    In simple energy balance terms, it takes about 390 W/m^2 at the surface to allow 239 W/m^2 to leave the system...
    No. This is a gross oversimplification of the problem, and will lead to errors. It is also flat out incorrect. Study this: Notice that the energy entering the system from outside is only 184 W/m2, and only 161 W/m2 of that is absorbed.
    In short, if it is going to take an additional 16.6 W/m^2 to allow 3.7 W/m^2 to leave the system to restore equilibrium, then why doesn't it take 1075 W/m^2 at the surface to allow the 239 W/m^2 from the Sun to leave the system at initial equilibrium (16.6/3.7 = 4.5; 1075/239 = 4.5)???
    Because your premise, that "it will take an additional 16.6 W/m2..." is incorrect.
    Response: [muoncounter] This gain theory/calculation was discussed in excruciating detail on Lindzen and Choi find low sensitivity. Please do not restart it here.
  10. Sphaerica (RE: 9) " It takes +16.6 W/m^2 at the surface for a 3 temperature rise. Where are you taking this from?" From the Stefan-Boltzman law. At a temperature of 288K, the surface emits about 390 W/m^2. At a temperature of 291K (+3C), the surface emits 406.6 W/m^2 (+16.6 W/m^2). "Again, where are you getting this math from? Do you have a source, or is it your own inference? [In simple energy balance terms, it takes about 390 W/m^2 at the surface to allow 239 W/m^2 to leave the system...] No. This is a gross oversimplification of the problem, and will lead to errors. It is also flat out incorrect. Notice that the energy entering the system from outside is only 184 W/m2, and only 161 W/m2 of that is absorbed." The total energy entering the surface is 239 W/m^2. Trenberth has 161 W/m^2 coming in directly from the Sun. The remaining 78 W/m^2 from the Sun he designates as absorbed by the atmosphere and brings it to the surface as 'back radiation'. Only it's not really 'back radiation' but 'forward radiation' that last originated from the Sun (as opposed to 'back radiation' as being energy that last originated from the surface). So, 239 W/m^2 incident on the surface becomes 396 W/m^2 from 157 W/m^2 of 'back radiation' from the atmosphere (239 + 157 = 396).
  11. 10, RW1,
    So, 239 W/m^2 incident on the surface becomes 396 W/m^2 from 157 W/m^2 of 'back radiation' from the atmosphere (239 + 157 = 396).
    Where do you get 157 of "back radiation"? Why do you treat the energy absorbed by the atmosphere as absorbed by the surface? Why and how do you use Stefan-Boltzman to compute the component 16.6 W/m2? FYI... These are rhetorical questions. I don't really want to know. Your entire model is invalid. You need to study more, and completely rethink things. There is no 1.6 amplification factor needed to allow an additional 3.7 W/m2 to leave the system. I still have no idea where you got your 16.6, or what you think it means.
    ...why doesn't it take 1075 W/m^2 at the surface to allow the 239 W/m^2 from the Sun to leave the system...
    You will never get an answer to this question because it is non-sensical. You need to look at things more carefully, probably abandon your current assumptions and perspective, and try to see if you can understand it properly. I suggest starting completely from scratch. I don't think that I can help you. You need an open mind, serious study time with books, and to let go of whatever it is you think that you know. There's a guy over at Nova's loony-bin site who does stuff like you're doing. If you're trying to learn by listening to him, you're only to wind up being get very, very confused.
  12. Sphaerica (RE: 11), "FYI... These are rhetorical questions. I don't really want to know." OK, then I won't answer. "Your entire model is invalid." I don't have a model. All of my numbers and calculations are from measured or generally accepted data. ['...why doesn't it take 1075 W/m^2 at the surface to allow the 239 W/m^2 from the Sun to leave the system...'] "You will never get an answer to this question because it is non-sensical." I'll probably never get an answer because this is a significant whole in the AGW theory that no one seems to be able to explain (that the system's response to GHG forcing will be much greater than it is to solar forcing). "I don't think that I can help you." I appreciate that you seem to be interested in helping me, but I'm not really interested in being helped per say. I'm a staunch skeptic of AGW, so my purpose here is to present contradictory evidence and logic that disputes the theory. That's what I'm doing. "There's a guy over at Nova's loony-bin site who does stuff like you're doing. If you're trying to learn by listening to him, you're only to wind up being get very, very confused." I'm not sure exactly who you are referring to, but I learn and have learned from listening to a multitude of sources - both for and against AGW. I don't care if it's from the Easter Bunny or Einstein - if I can understand it and not find fault in the evidence, reasoning and logic behind it, I accept until it's been adequately challenged or discredited. I have not seen, in my estimation, these relatively simplistic things explained by the pro-AGW advocates.
    Response: [DB] Please, everyone, RW1 has amply demonstrated over many threads and in comments almost beyond number that he's not interested in learning anything here (by his own admission), but only in putting his own brand of logic and and calculus on display. Thank you all for the good faith efforts, but DNFTT. Thanks!
  13. RW1, That word doesn't mean what you think it means. A skeptic ~is~ interested in being helped. You have described something else.
  14. 12, RW1,
    I don't have a model.
    Of course you do. Everything in science is a model. You have a mathematical model (a set of rules and assumptions) that you've used to derive your proposed answer from the data. But that model -- the rules and assumptions you are following -- are flawed.
    ...the system's response to GHG forcing will be much greater than it is to solar forcing...
    This is untrue. You are the only person on the planet to have arrived at this conclusion, because your underlying model (understanding) is flawed.
    ...my purpose here is to present contradictory evidence and logic that disputes the theory. That's what I'm doing.
    No, what you're doing is confusing people with your own personal creation of faux-math-science.
    I have not seen, in my estimation, these relatively simplistic things explained by the pro-AGW advocates.
    No one can explain to you why 2 plus A does not equal monkeys, because it's not even a mathematical equation. Similarly, your insistence that some theory must explain your 1075 W/m2 number will never happen.
    I'm a staunch skeptic of AGW
    That's an oxymoron. No one can be a "staunch" skeptic. Being skeptical means questioning what you are first shown until it is satisfactorily proven, not questioning it endlessly with no hope of acceptance or understanding, because you staunchly refuse to be anything but eternally skeptical.
    Response: [Muoncounter] We've been down this painful road before. Please do not encourage another go round. The other player in the drama is known as co2isnotevil, which should tell you all you need to know about his viewpoint.
  15. Sorry, but I'm not interested in a semantics debate regarding the definition 'skeptic'. ['...the system's response to GHG forcing will be much greater than it is to solar forcing...'] "This is untrue. You are the only person on the planet to have arrived at this conclusion, because your underlying model (understanding) is flawed." I don't see how this is untrue. I make no claim that it's an impossibility, but it is true that the AGW theory claims the next 3.7 W/m^2 incident on the surface will be amplified by the system nearly 3 times a much as the original 239 W/m^2 incident on the surface from the Sun. If, as the AGW theory claims, an additional 3.7 W/m^2 at the surface is to become 16.6 W/m^2 mostly through positive feedback, quantify specifically how the feedback causes this much change while it doesn't for the original 98+% (239 W/m^2) from the Sun. "But that model -- the rules and assumptions you are following -- are flawed." Explain why.
  16. Dessler 2010 seems to be claiming that clouds are trapping more energy as the surface warms. He writes on page 3 of his paper: "Because I have defined downward flux as positive, the positive slope here means that, as the surface warms, clouds trap additional energy; in other words, the cloud feedback here is positive." Is he claiming that clouds are changing in a way that results in them trapping more surface energy? If yes, how has he rectified this with all the data (i.e. how has he shown that the additional energy the clouds trap is greater than the additional energy they reflect away)???
    Response: [Muoncounter] There is an existing thread for Dessler's paper; check to see if your question was already addressed.
  17. RW1, No. You misunderstand, and then cling to your misconceptions. You need to spend less time lecturing, and more time reading and studying, to figure out for yourself where your own mistakes are. End of "debate."
  18. @RW1 9of17 comments to this post, so far. You are likely to get soon a DNFTT banner in your comments and I'd like to explain why is that. T - "If I throw this stone into the water it'll float" P - "No, it'll sink, stone's density is higher that water's" T - No, it'll clearly sink. Don't you see the weight of the stone is less than the weight of the water, you, idiot? M - DNFTT You might think that the trolling part is "you, idiot", but that is clearly just something said on the heat of the debate and doesn't affect the intellectual content of it, so it's easily dismissed. The trolling part is simply the underlying lie about the world of Physics: the twisted pricipia that things float if they amount a lesser weight. The "no" and the "you, idiot" part just reinforces the idea that the troll has made his/her mind -nobody cares about how or why- and he/she's simply "trolling around". I suppose that many fellows who think that there's a "global warming hoax" of some kind, sort of they come to websites like this "to get our voices heard about that outrageous subject", and that they experience comforting feelings if they overflow threads and the comment sections and then get a trolling banner just for "hitting the nerve" and as a result of "the nuisance their witty remarks provoke". Please, don't fool yourself with such naïvités. You're in an academical site and you have the ethical obligation of being diligent in detecting or correcting any wrong product of you animus. It also happens that the fact that you detect the gruesome mistake in the 'floating' example doesn't mean you are not gruesomely mistaken just because you cannot detect it. The principle for (legally) capable people that states "nobody can argue his own slowness and clumsiness to justify an error" comes from that obligation of diligence. In sites like this it translates in a diligent revision of your knowledge matrix once it has being pointed at you gruesome conceptual mistakes. The worst thing it could happen is that you learn something.
  19. #18 ERRATUM: Where it say "No, it'll clearly sink." it must say "No, it'll clearly float."
  20. @ RW1 In the interest of fairness I offer some (unsolicited) advice: I in no fashion mean to downplay your sincerity in your beliefs from what you've learned from G White and the like. In order to help you better convey your position with greater clarity, I suggest you learn to better discern the point between where established physics and that you've learned from Mr. White diverge. If you can serve that divergence up with clarity and precision, I think then that others will be better able to understand you. It will necessarily entail (as Sphaerica has pointed out with greater eloquence than I), however, temporarily setting aside those learnings and preconceptions gained from the table of Mr. White to leap into mainstream physics deep enough to better educate yourself on where that difference lies, so you can then relate that point to others. At that point you should also be then able to construct tests for your hypothesis that can then be examined by others. In short, you will have a publishable basis for submission to peer-review. HTH, The Yooper
  21. Daniel (RE: 20), "I in no fashion mean to downplay your sincerity in your beliefs from what you've learned from G White and the like. In order to help you better convey your position with greater clarity, I suggest you learn to better discern the point between where established physics and that you've learned from Mr. White diverge. If you can serve that divergence up with clarity and precision, I think then that others will be better able to understand you. It will necessarily entail (as Sphaerica has pointed out with greater eloquence than I), however, temporarily setting aside those learnings and preconceptions gained from the table of Mr. White to leap into mainstream physics deep enough to better educate yourself on where that difference lies, so you can then relate that point to others." Where does the difference between "established physics" lie ? This is what I don't understand. These kinds of responses are not scientific discussion - they're just empty platitudes. Yes, it's no secret I've spent a considerable amount of time studying GW's research and he has been very generous to me. However, I am not "accepting" his research on the basis of his authority or generosity toward me (nor, I'm sure, would he want me to). I've largely accepted it by examining it in detail and weighing it against all the other evidence. But look, I'm not here to discuss GW - I'm here to discuss cloud feedbacks, and would like to get back on topic and return to scientific give and take discussion.
  22. 21, RW1,
    Where does the difference between "established physics" lie ? This is what I don't understand.
    And this is the crux of your problem. You need to do two things: 1) Present your own model more clearly. You skip steps, make leaps, then get frustrated when other people can't figure out where you get your numbers from. You even claimed that you didn't have a model! 2) You are the outlier. You are the one with the unconventional point of view. The burden is yours to explain your position, but more importantly to study (as the rest of us have) to learn what the mainstream science says. If you can't see the difference between what you put forth, and what everyone else already understands, the burden falls upon you to educate yourself to eliminate that gap. You can't just demand that everyone answer your questions, when you don't demonstrate a clear grasp of the established science, or when you make incorrect statements that clearly are not in line with the established science, and yet even when this is pointed out, you can't see the difference, stomp your feet, and get flustered. You can complain that something is incorrect if you can demonstrate that you understand things, and can yourself clearly explain where your position diverges. You cannot, on the other hand, complain that you don't know why people can't answer your questions, and yet refuse to consider other points of view yourself. You also should not be adopting the tone that you are right, all of main stream climate science is wrong, and so everyone else owes it to you to prove to you that you are mistaken. Like it or not, you are the outlier. If you want to "sell" your position, you need to do that, by convincing other people, not by demanding that they convince you.
    Response: [muoncounter] RW1 has explained his position in considerable detail on the Lindzen and Choi thread; it is not necessary to start that up again. He is correct in expressing an interest in staying on topic.
  23. As far as I can see RW1 believes that you can infer feedback relationships from the Trenberth state diagram (ie the comments about gain) and then use these no.s to project what the diagram would look like for say doubled CO2. When the no.s dont accord with those calculated properly, then RW1 claims physics is wrong.
  24. Sphaerica (RE: 22), "1) Present your own model more clearly. You skip steps, make leaps, then get frustrated when other people can't figure out where you get your numbers from. You even claimed that you didn't have a model!" What specifically do you want me to explain? I agree with the moderator that a lot of this has been covered in previous discussions, but if you ask any direct question, I'll do my best to answer it. At any rate, I'd like to get back on topic with a question: If clouds are not the primary mechanism modulating the energy balance, and are instead acting to greatly amplify relatively small temperature changes, then what is the primary mechanism controlling the energy balance of the planet?
  25. 24, RW1,
    If clouds... are instead acting to greatly amplify relatively small temperature changes...
    They are not "greatly amplifying" small temperature changes. They do have some impact, but there's no reason to exaggerate things with "great" and "small" to try to score points.
    ...what is the primary mechanism controlling the energy balance of the planet?
    I'm not sure why there must be a primary mechanism, and because there are multiple mechanisms, they all interact, they are all difficult to "force," and it becomes a question of semantics in arguing over which is "primary." The mechanisms available for altering climate are:
    • Solar insolation (barely changes)
    • Orbital forcings (changes predictably on huge time scales)
    • CO2 (changes on any of 3 time scales, geologic=very slow, natural feedback=medium, anthropogenic=very fast
    • H2O (changes relatively quickly in direct proportion to temperature, and so it is the primary amplifier in power, but not a controller since it exerts no independent control of its own)
    • Albedo (can change relatively quickly, or slowly, but almost always as a response to other factors)
    • Clouds (change almost instantaneously, and positive/negative effects are arguable, but relatively inconsequential compared to the bigger factors).
    • Land mass dispositions (which greatly affect albedo and the results of orbital forcings, but which only themselves vary on massively long timescales)
    Which is primary? At the onset and termination of glacial periods, the orbital forcings, but only through an albedo feedback, and in conjunction with a strong CO2 feedback, which in turn operates in conjunction with the strong H2O feedback. Outside of those periods of orbital forcings, under natural conditions, CO2 is the main long term driver, amplified by albedo, cloud and H2O feedbacks. During anthropogenic pollution, CO2 is the only control mechanism that operates on the time scales that we are witnessing, again amplified by all of the usual feedbacks.

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