A paper published Friday in the Journal of Geophysical Research (GRL) finds that a known and natural atmospheric oscillation, the Southern Annular Mode or SAM, is correlated with observed increases in cloud cover resulting in regional cooling of approximately -2.5C. See for example this comparison from the paper with MODIS satellite data:
From UCAR:
The Southern Annular Mode (SAM), which is defined by changes in the westerly winds that are driven by temperature contrasts between the tropics and southern polar areas. The annular modes generally take a circular pattern (‘annular’ means ring-shaped) and see-saw between positive and negative phases for weeks or months. In the SAM’s positive mode, the ring is stronger and further south, inhibiting Antarctic air outbreaks. In the negative mode, a weaker, more variable vortex allows Antarctic air to spill north more easily.
The Southern Annular Mode has steadily trended positive in recent decades. Computer models indicate this trend is related to ozone depletion above Antarctica and increases in greenhouse gases. (Image courtesy Jianping Li, China Institute for Atmospheric Physics.)
As presently programmed, climate models assume clouds result in net positive feedback and increased temperatures, however this new paper and several others that have recently been published show that clouds instead result in net negative feedback and cooling.
Key Points of the paper:
- Sudden regional increases in cloud cover are detected over S. America
- Changes linked to the Southern Annular Mode
- The cloud changes are associated with regional temperature reductions
The paper and abstract:
Understanding sudden changes in cloud amount: The Southern Annular Mode and South American weather fluctuations
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, D13103, 7 PP., 2012
doi:10.1029/2012JD017626
Benjamin A. Laken Instituto de Astrofísica de Canarias, La Laguna, Spain, Department of Astrophysics, Faculty of Physics, Universidad de La Laguna, La Laguna, Spain
Enric Pallé Instituto de Astrofísica de Canarias, La Laguna, Spain, Department of Astrophysics, Faculty of Physics, Universidad de La Laguna, La Laguna, Spain
This work investigates the cause and effects of extreme changes in synoptic-scale cloud cover operating at daily timescales using a variety of satellite-based and reanalysis data sets. It is found that the largest sudden increases detected in globally averaged cloud cover over the last ten years of satellite-based observations occur following positively correlated shifts in the phase of the Southern Annular Mode (SAM) index. The associated pressure anomalies are found to generate frontal cloud formation over large areas of the South American continent, increasing regional cloud cover by up to 20%; these changes are correlated to statistically significant reductions in local temperatures of approximately −2.5°C with a +1 day time lag, indicating the SAM index is associated with large scale weather fluctuations over South America.
It’s no surprise that clouds are a negative (cooling) feedback. A warming cloud feedback is just a fiddle in the models.
A positive correlation with the Southern Annular Mode (SAM) index surprises me. I’d expect a negative correlation. More polar outbreaks = more clouds.
What strikes me is the fact that a paper so trivial is considered “novel”.
Pure logic will tell you that clouds cannot have a positive feedback, since if they had, the Earth would have been destroyed long time ago. And if they do not have a positive feedback they must have negative one.
I am hoping to put together an article on the site I post to, about all the various negative feedback research papers which seem to have come out in the past year (hints would be appreciated! 😛 ), in regards to their clearly opposite nature to the Positive feedbacks figured for the same, in the climate models.
So if ya’ll don’t mind, two questions:
1. Are there NO negative feedbacks at all, in the models?
2. I don’t understand how clouds could possibly be a positive feedback- it just seems to me to suggest, that they posit some kind of roof over the atmosphere, as though Nothing could escape into space…
I rather like this understated way of suggesting the the models “indicate a trend” rather than prove that we’re all doomed
@Eyal Porat says “Pure logic will tell you that clouds cannot have a positive feedback, since if they had, the Earth would have been destroyed long time ago.”
That may be pure logic, but it is wrong. The largest feedback is the increase in longwave IR radiation from the earth caused by an increase in temperature. The system remains stable, with net negative feedback as long as the sum of the various positive feedbacks are less then this dominant Stefan–Boltzmann. In most climate science literature, a “net positive” feedback refers to only those terms other than the overwhelming Stefan–Boltzmann feedback term. It’s a confusing choice of terminology, but climate scientist often use different terms for things well know I other fields.
If clouds were a positive feedback it would follow that if clouds were made to completely cover the earth the global average temperature would increase.
Who can justify why this should be true?
I can envisage that cloud cover at night would slow cooling as in the day it would slow warming but I find it difficult to understand how the slowed cooling could be greater that the slowed warming.
Just one of the reasons I’m a sceptic when it comes to CAGW.
Seems some people have confusion about the warming and cooling roles of clouds … lots of technical references on this, but a simple statement from Wikipedia: “Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect.”
Edits:
negative cloud feed associated with SAM — feedback ??
climate scientists … well known in other fields ??
otter…i would LOVE to see that when you are finished. can you tell us what site you post to?
These scientists,
http://www.agu.org/pubs/crossref/2010/2009GL041320.shtml
estimate an increase in wind speed of less than half a metre per second per decade since early 1980s has made these seas choppier, resulting in more aerosols which give more cloud nuclei, resulting in an 85% increase in some regions.
Would that be more cloud cover or more intense weather systems?
Either way wouldn’t in result in an intensification of pressure systems and so more aerosol production?
They say it results in a substantial negative climate feedback.
“The change in cloud drop concentrations causes an increase in cloud reflectivity and a summertime radiative forcing between at 50 and 65°S comparable in magnitude but acting against that from greenhouse gas forcing over the same time period, and thus represents a substantial negative climate feedback.”
Bradley
In the SAM’s positive mode, the ring is stronger and further south, inhibiting Antarctic air outbreaks
http://virakkraft.com/SAM-temp-SH.png
Otter says:
Yes…There is the lapse rate feedback. That feedback says that the temperatures at the altitude most important for radiating infrared radiation back out into space tend to increase more rapidly with warming than the temperature at the surface and hence that it takes a smaller surface temperature warming to counteract a certain forcing than would otherwise be the case.
This negative feedback involves a lot of the same physics as the water vapor feedback (a positive feedback). Hence, models that have a larger (in magnitude) lapse rate feedback tend to have a larger in magnitude water vapor feedback. This means that although there is a fair bit of variation in the lapse rate feedback between models, there is much less variation in the sum of the two feedbacks.
There seems to be a constant confusion among AGW skeptics between the radiative effect of clouds and the feedback from clouds. To determine the feedback due to clouds, you have to know both the radiative effect and the effect of increasing temperature on clouds. (And, it is not intuitively obvious how clouds vary with temperature. You might think that since water vapor increases with temperatures, clouds do too. However, the saturation vapor pressure also increases with temperature. And, in fact the water vapor is expected to increase with temperature in such a way that the average relative humidity will stay pretty close to constant or more even decrease slightly.)
So, even though the net radiative effect of clouds is negative (i.e., clouds on average cool due to increasing albedo more than they warm due to a greenhouse effect of reducing the escape of IR radiation from the Earth to space), if the effect of increasing temperature in the current climate is to reduce cloudiness rather than increase it, then this could be a positive feedback…i.e., cause additional warming.
As it turns out, there is the additional complication that although the net radiative effect of all clouds is cooling, the sign of the effect can vary with the type of cloud: Low clouds tend to have a net radiative cooling effect (because the albedo effect wins out over the greenhouse effect) but high clouds tend to have a net radiative warming effect (because the greenhouse effect wins out over the albedo effect). [These basic principles are not controversial, by the way: Skeptical atmospheric scientist Richard Lindzen’s iris hypothesis proposed that warming in the tropics would decrease high clouds and therefore produce a negative feedback.]
Truth is an iterative process. First you admit that clouds cool by day. Then you admit the same cooling occurs with only the slight delay of OLR at night. Finally you admit that ‘slower cooling’ is NOT warming.
Clouds are not static stage props. The multiple layers of vertical wind shears within a cloud come from the very nature of clouds, ‘boiling’ in mid air with high velocity invisible water vapor rising past colums of newly condensed cold droplets falling inside clouds.
In my article “Science Goes Over-Under, Inside-Out” I describe my thoughts on clouds while sitting alone….inside a cumulus cloud….in a Cessna 150. This massive convective energy transfer from cloud bottoms to cloud tops has NO radiative component and is hence not in the non sequitur K-T budget. Be a Joanie Mitchell and “Look At Clouds from Both Sides Now”.
charliexyz says:
July 7, 2012 at 3:52 am
@Eyal Porat says
The IR radiation could not have happen if the clouds covered the earth completely. They may hold some of the radiation from going back to space, but the initial cause of the IR radiation (i.e. the sun) is the existence/lack of clouds.
So they are a mitigating factor = negative feedback.
Hence their feedback is not net negative, but the overall effect is: more clouds -> less heat reaches the earth -> cooling, and vice versa.
I seriously doubt and contest that ozone has anything to do with climate. It is too high and to thin to have the effect or abilities that they attribute to it. Just as with CO2, they have this gas bias and give it superpowers.
fredb says: July 7, 2012 at 4:12 am
“Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; ”
Er, No. The IR radiated downward has no effect on the surface as those energy levels are already full. It has to be reflected back upward. Clouds simply slow the loss of IR to space, but back radiation does not exist as a factor that does anything.
The paragraph that begins “As presently programmed…” does not seem to be from the UCAR cite. Perhaps this was an editing error.
https://www2.ucar.edu/news/backgrounders/weather-maker-patterns-map-text-version
Is this the same as the paper on ‘The Iris Effect’ ?
Hey! What about the recent contiguous continental US heatwave? Is this related to a DECREASE in cloud cover over the region?
There has been a noted 5% or so reduction in cloud cover globally over the past 50 years (the data is poor from what I’ve seen, like the CERES project). If things like SAM increase cloud cover by 20% in South America, there must be equal areas that have decreases of 15% to maintain the average (if S.America is the only area of net increase).
I worked up a paper on cloud cover changes in the central UK that accounted for the central UK temperature changes (plus PDO/AMO patterns) (NothingSettledNothingCertain.com). My work and this paper (and others) confirm to me the suspicion that most of global warming was not global but regional. Global warming is an aretefact of addition and division. The human tendency to generalize from the specific, and to bias all thoughts to support personal experience, means that Americans seeking refuge from a heatwave see the world warming catastrophically. If – as in the early ’70s? – the American Heartland was plunged into a freezer while Europe broiled, America would be worried about (again) a returning Ice Age.
The Russian heatwave and the current American heatwave: is this a cloud cover effect or a “global warming” effect? I’m betting on cloud cover. I recall grandparents who spoke of their mothers crying on the farmhouse steps because another day had started out with beautiful, blue skys – a routine, I was told, that lead to 7 years of failed crops in southern Saskatchewan.
It always seems to come back to clouds. Svensmark clouds, that is.
The important thing is convection, which serves as a kind of “end run” around the greenhouse effect. Clouds are incidental to convection. The significant effect of clouds is to moderate temperature swings, which should theoretically result in some warming because outgoing radiation goes as the fourth power of surface temperature. Also, assuming that increased albedo will result in cooler surface temperature ignores the fact that both the surface and the cloud are approximately greybodies and so should behave nearly the same with respect to incident radiation.
The big negative feedback is simply convection, which causes a parcel of air that is heated above a temperature given by the adiabatic lapse rate to rise to a level where it can “see” space and get rid of the excess heat. The presence of moisture augments this process because now phase change (rain) helps to move the heat upward and overcomes any tendency of clouds to warm the surface. Incidentally, the moisture content of the atmosphere is also set by the adiabatic lapse rate, so assuming any positive feedback on surface temperature from moisture content is questionable ab initio. Any process that does not help the earth to reject heat is not energetically favorable because it retards the increase in entropy that the universe is trying so valiantly to achieve. Perhaps that’s why CO2 concentrations have been so low for so long, before we arrived.
Yes, greenhouse gases will produce backscattered radiation at the surface and feed thousands of climate scientists with no other means of support, but convection will reduce the effect to insignificance.
Joel Shore:You might think that since water vapor increases with temperatures, clouds do too. However, the saturation vapor pressure also increases with temperature. And, in fact the water vapor is expected to increase with temperature in such a way that the average relative humidity will stay pretty close to constant or more even decrease slightly.)
Yes, but the problem with the above is that air does not stay at one average temperature typically over the course of a day(or a year). Rather it warms, then cools in sequence. Given a more or less constant RH, per the Clausius-Clapeyron relationship, then a warmer on average air mass will condense a greater amount of moisture than a cooler one.
It is pretty hard to square this relationship without assuming that cloud feedback is negative with regard to temperature.
Cheers, 🙂
pochas says:
This does not make sense. Convection can’t do an “end run” around the greenhouse effect because ultimately the energy has to escape the Earth system via radiation. To the extent that one can make something sensible out of your argument, what it would imply is the notion that the mid- and upper- troposphere can heat up without the surface temperature heating up too…but, to the extent that this is true, it is already accounted for by the lapse rate feedback. There is no evidence that this effect is being underestimated. (In fact, some people claim that the supposed lack of the so-called “tropical hotspot” in the troposphere is evidence that it is being overestimated, although the wiser money is probably on the notion that it reflects residual problems with long-term trends in some of the satellite and radiosonde data analyses. Still, the notion that the amplification is actually much larger than the models predict certainly is something with no experimental support.)
Shawnhet says:
My point is simply that the complexity of the issues defies attempts to reach very simple conclusions about how clouds will behave in a warming climate. Your intuition that cloudiness will increase contradicts Lindzen’s intuition that at least some types of clouds (high clouds in the tropics) will decrease. That ought to give you pause if you think that you can come to a conclusion on the basis of any extremely simple ideas.
charliexyz says:
July 7, 2012 at 3:52 am
You do realize you haven’t one iota of evidence for any of the garbge you regurgitated?
“So, even though the net radiative effect of clouds is negative (i.e., clouds on average cool due to increasing albedo more than they warm due to a greenhouse effect of reducing the escape of IR radiation from the Earth to space), if the effect of increasing temperature in the current climate is to reduce cloudiness rather than increase it, then this could be a positive feedback…i.e., cause additional warming.”
1) You’re defining the “greenhouse effect” as a reduction in the escape of IR radiation from the Earth into space, yet in a real greenhouse the warming (inhibition of cooling) seen is due to an inhibition of air movement rather than an entrapment of IR radiation. (Empirical experimentation has demonstrated this time and again.) In the real world atmosphere air movement results from temperature differentials. One can empirically measure the fact that when it is cloudy at night the temperature differential between the ground and the air is reduced by about 1/2. This significantly decreases the vigor of nighttime upward convection currents and naturally results in a slower rate of nighttime ground cooling. This is, indeed, a quasi-greenhouse effect, but it is caused by a reduction in air flow rather than the entrapment of IR radiation. In the absence of clouds regardless of the level of humidity (the primary greenhouse gas) the temperature differential between the air and the ground *increases* during the course of the night, which is an anti-greenhouse effect. This anti-greenhouse effect seen on cloudless nights is a repetitive, observable phenomenon that can be measured by anyone anywhere in the world with two thermometers; one about 1.5 meters off of the ground and one placed at ground level. After placing the thermometers take readings every thirty minutes during the night and you will observe that as the cloudless night progresses the temperature differential between the ground and the air will widen, regardless of how humid it is. An extreme form of the quasi-greenhouse effect that low-level nighttime clouds create can be seen during a nighttime temperature inversion. Such temperature inversions are invariably accompanied by a dead calm.
2) The hypothetical warming affect of increased CO2 levels is said to be augmented by a resultant increase in humidity, which further warms the atmosphere, which leads to further evaporation of water and even more humidity. Within which empirical study of the climate has an increase in humidity led to a decrease in cloud cover?
According to the “greenhouse effect” hypothesis even the lessor GHG’s, like CO2, require the presence of water vapor, i.e., water vapor feedback, to have a significant affect on the temperature. Therefore, when and where it is both hot and dry the heat cannot be the result of the “greenhouse effect” since the hypothetical “greenhouse effect” is dependent upon water vapor for its operation. Ergo, the humidity in Huntsville, Alabama cannot be the cause of the heat present in Death Valley, CA., which is on average several degrees C warmer than Huntsville. So, Huntsville, whose air is flooded with the greenhouse gas water vapor, is not only cooler; it is also teaming with life, while arid Death Valley, which is greenhouse gas deficient, i.e., very little water vapor, is not only hotter; it’s ability to support life is severely limited. The “greenhouse effect” hypothesis asserts that it would be a climate catastrophe if the world becomes more and more like Huntsville and less and less like Death Valley; that is, becomes more and more humid.
Carl