I thought this post on clouds and climate modeling below from Steve McIntyre’s Climate Audit was interesting, because it highlights the dreaded “negative feedbacks” that many climate modelers say don’t exist. Dr. Richard Lindzen highlighted the importance of negative feedback in a recent WUWT post.
One of the comments to the CA article shows the simplicity and obviousness of the existence of negative feedback in one of our most common weather events. Willis Eschenbach writes:
Cloud positive feedback is one of the most foolish and anti-common sense claims of the models.
This is particularly true of cumulus and cumulonimbus, which increase with the temperature during the day, move huge amounts of energy from the surface aloft, reflect huge amounts of energy to space, and fade away and disappear at night.
Spot on Willis, I couldn’t agree more. This is especially well demonstrated in the Inter Tropical Convergence Zone (ITCZ) The ITCZ has been in the news recently because early analysis of the flight path of Air France 447 suggests flying through an intense thunderstorm cell in the ITCZ may have been the fatal mistake. There is a huge amount of energy being transported into the upper atmosphere by these storms.
Here are some diagrams and photographs to help visualize the ITCZ heat transport process. First, here is what the ITCZ looks like from space. Note the bright band of cumulonimbus clouds from left to right.
Here is a pictorial showing a cross section of the ITCZ with a cumulonimbus cloud in the center.
And finally, a 3D pictorial showing ITCZ circulation and heat transport. Note the cloud tops produce a bright albedo, reflecting solar radiation.
And here is the post on Climate Audit
Cloud Super-Parameterization and Low Climate Sensitivity
“Superparameterization” is described by the Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity in an online meeting report (Bretherton, 2006) as:
a recently developed form of global modeling in which the parameterized moist physics in each grid column of an AGCM is replaced by a small cloud-resolving model (CRM). It holds the promise of much more realistic simulations of cloud fields associated with moist convection and turbulence.
Clouds have, of course, been the primary source of uncertainty in climate models since the 1970s. Some of the conclusions from cloud parameterization studies are quite startling.
The Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity reported that:
The world’s first superparameterization climate sensitivity results show strong negative cloud feedbacks driven by enhancement of boundary layer clouds in a warmer climate.
These strong negative cloud feedbacks resulted in a low climate sensitivity of only 0.41 K/(W m-2), described as being at the “low end” of traditional GCMS (i.e. around 1.5 deg C/doubled CO2.):
The CAM-SP shows strongly negative net cloud feedback in both the tropics and in the extratropics, resulting in a global climate sensitivity of only 0.41 K/(W m-2), at the low end of traditional AGCMs (e.g. Cess et al. 1996), but in accord with an analysis of 30-day SST/SST+2K climatologies from a global aquaplanet CRM run on the Earth Simulator (Miura et al. 2005). The conventional AGCMs differ greatly from each other but all have less negative net cloud forcings and correspondingly larger climate sensitivities than the superparameterization
They analyzed the generation of clouds in a few leading GCMs, finding that a GCM’s mean behavior can “reflect unanticipated and unphysical interactions between its component parameterizations”:
A diagnosis of the CAM3 SCM showed the cloud layer was maintained by a complex cycle with a few hour period in which different moist physics parameterizations take over at different times in ways unintended by their developers. A surprise was the unexpectedly large role of parameterized deep convection parameterization even though the cloud layer does not extend above 800 hPa. This emphasizes that an AGCM is a system whose mean behavior can reflect unanticipated and unphysical interactions between its component parameterizations.
Wyant et al (GRL 2006) reported some of these findings. Its abstract stated:
The model has weaker climate sensitivity than most GCMs, but comparable climate sensitivity to recent aqua-planet simulations of a global cloud-resolving model. The weak sensitivity is primarily due to an increase in low cloud fraction and liquid water in tropical regions of moderate subsidence as well as substantial increases in high-latitude cloud fraction.
They report the low end sensitivities noted in the workshop as follows:
We have performed similar +2 K perturbation experiments with CAM 3.0 with a semi-Lagrangian dynamical core, CAM 3.0 with an Eulerian dynamical core, and with the GFDL AM2.12b. These have λ’s of 0.41, 0.54, and 0.65 respectively; SP-CAM is about as sensitive or less sensitive than these GCMs. In fact, SPCAM has only slightly higher climate sensitivity than the least sensitive of the models presented in C89 (The C89 values are based on July simulations)…
The global annual mean changes in shortwave cloud forcing (SWCF) and longwave cloud forcing (LWCF) and net cloud forcing for SP-CAM are _1.94 W m_2, 0.17 W m_2, and _1.77 W m_2, respectively. The negative change in net cloud forcing increases G and makes λ smaller than it would be in the absence of cloud changes.
Wyant et al (GRL 2006) is not cited in IPCC AR4 chapter 8, though a companion study (Wyant et al Clim Dyn 2006) is, but only in the most general terms, no mention being made of low sensitivity being associated with superparameterization:
Recent analyses suggest that the response of boundary-layer clouds constitutes the largest contributor to the range of climate change cloud feedbacks among current GCMs (Bony and Dufresne, 2005; Webb et al., 2006; Wyant et al., 2006). It is due both to large discrepancies in the radiative response simulated by models in regions dominated by lowlevel cloud cover (Figure 8.15), and to the large areas of the globe covered by these regions…
the evaluation of simulated cloud fi elds is increasingly done in terms of cloud types and cloud optical properties (Klein and Jakob, 1999; Webb et al., 2001; Williams et al., 2003; Lin and Zhang, 2004; Weare, 2004; Zhang et al., 2005; Wyant et al., 2006).
(Bretherton 2006)
Dessler et al (GRL 2008) made no mention of strong negative cloud feedbacks under superparamterization, stating that sensitivity is “virtually guaranteed” to be at least several degrees C, unless “a strong, negative, and currently unknown feedback is discovered somewhere in our climate system”:
The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhouse gas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.
There are a limited number of possibilities for such a possibility, but it is interesting that cloud super-parameterizations indicate a strong negative cloud feedback (contra the standard Soden and Held results.)
This is not an area that I’ve studied at length and I do have no personal views or opinions on the matters discussed in this thread.
References:
Bretherton, C.S., 2006. Low-Latitude Cloud Feedbacks on Climate Sensitivity. Available at: www.usclivar.org/Newsletter/VariationsV4N1/BrethertonCPT.pdf [Accessed June 12, 2009].
Wyant, M.C., Khairoutdinov, M. & Bretherton, C.S., 2006. Climate sensitivity and cloud response of a GCM with a superparameterization. Geophys. Res. Lett, 33, L06714. eos.atmos.washington.edu/pub/breth/papers/2006/SPGRL.pdf
Bretherton, C.S., 2006. Low-Latitude Cloud Feedbacks on Climate Sensitivity. Available at: www.usclivar.org/Newsletter/VariationsV4N1/BrethertonCPT.pdf [Accessed June 12, 2009].
Wyant, M.C., Khairoutdinov, M. & Bretherton, C.S., 2006. Climate sensitivity and cloud response of a GCM with a superparameterization. Geophys. Res. Lett, 33, L06714.
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How do they get away with ignoring clouds negative feedback?
This is the real climate denialism.
common sense suggest coulds would be a negative feedback, otherwise the earth would have suffered runaway warming in the past.
I wander if anyone monitors pyrgeometer data globally to see if downward radiated infrared energy at night during clear skies has increased at all? Wouldnt this show if there was any enhancement of the greenhouse effect or not? Clouds certainly reflect infrared back down but also block the incoming shortwave energy which carries greater energy than that reflected back making then a negative effect.
I think I’ve never heard so loud
The quiet message in a cloud.
===================
Somewhat OT – this new publication in the current issue of Nature (June 11-09), as presented by Science Daily, makes a bold claim:
Title “Carbon Emissions Linked To Global Warming In Simple Linear Relationship” – and excerpt: “… These findings mean that we can now say: if you emit that tonne of carbon dioxide, it will lead to 0.0000000000015 degrees of global temperature change. If we want to restrict global warming to no more than 2 degrees, we must restrict total carbon emissions – from now until forever – to little more than half a trillion tonnes of carbon, or about as much again as we have emitted since the beginning of the industrial revolution.”
http://www.sciencedaily.com/releases/2009/06/090610154453.htm
of course, it’s mostly based on modeling…
Such simplistic linearity seems like utter balderdash to me, but I haven’t read the full paper yet. Any insights and comments?
“How do they get away with ignoring clouds negative feedback?”
Ask the blokes over at RealClimate!
Now we know why the heat is not in the oceans.
AGW community members still amenable to science will modify their positions, based on this.
Roy Spencer demonstrates very strong negative feedback here: http://www.drroyspencer.com/research-articles/satellite-and-climate-model-evidence/ which shows feedback of 8 W m-2 K-1.
Together, the CERES data from two separate satellites thus display evidence of what I have used a simple model to explain theoretically: strong negative feedback is observed to occur on shorter time scales in response to non-radiative forcing events (evaporation/precipitation), which are superimposed upon a more slowly varying background of radiative imbalance, probably due to natural fluctuations in cloud cover changing the rate of solar heating of the ocean mixed layer.
http://www.videnskab.dk/content/dk/blogs/bloggen_fra_stratosfaren
The Danish Meteorological Institute (DMI) blog from a scientific project in the ITCZ zone….Written in danish language…if you use a Google-translation it may make sense.
“How do they get away with ignoring clouds negative feedback?”
Who is? No one.
Fact is there are both negative and positive cloud feedbacks. The question is which one (if any) predominates if the world warms.
Here is a little bit of ‘home and garden’ style climatology. Let’s think of the Earth in terms of functional zones in terms of cloud cover.
1. The Inter Tropical Convergence Zone. Here, cumulus cloud is strongly convective. The convecting atmosphere loses heat primarily by decompression, the same process used in refrigeration. So, these zones emit relatively low levels of outgoing long wave radiation. As the tropics has warmed OLR has fallen. So, not much scope for a greenhouse effect there.
2. The relatively cloud free (in term of low cloud) zones of the trade wind zone. Here, air that is close to the surface is being warmed as it travels towards the equator so not much chance of cloud formation. So, no chance of a greenhouse effect here from back-radiation.
3 The traveling high pressure cells of the ‘Hadley circulation’ that return air from the upper troposphere to the surface at about 30°North and 30°South. This air is dry for obvious reasons. It is being warmed by compression. Lots of outgoing long wave radiation here but very little cloud or water vapour to act as a feedback mechanism.
4. The rest. Mostly it could do with a little extra warmth so it can be ignored.
A complication: Area 2 has high level ice cloud called cirrus generated at the ITCZ. The evidence is that this zone of the upper troposphere heats and cools with the change in stratospheric ozone that goes along with the QBO. As ozone levels increase in the middle stratosphere the upper troposphere is observed to warm. Logically, the cloud evaporates. At any rate, this is the time when the sea is observed to warm. That’s not due to feedback. Its due to more solar radiation getting to the surface of the ocean.
When I read the stuff that climate modelers talk about I am overcome with a strong desire to give these guys some lessons in elementary geography. Mathematics may be the language of science but great mathematics based on false premises and faulty equations produces ‘spew’.
Or
RealClimate denialism
I’ve seen the airflow (heat transport) diagrams for years but never with any actual numbers quantifying how much heat energy is moved to the upper atmosphere and eventually radiated into space. How good is the understanding of this at the micro and grid-cell level?
So just to make this clear for dummies like me.
When the earth gets hotter, we get more clouds reflecting energy away from the earth, bringing the earth back towards its “natural” energy state.
When the earth gets colder, we get less clouds reflecting energy away from the earth, bringing the earth back towards its “natural” energy state.
That seems to be pretty sensible. After all, if the climate system was unstable, and could run away if unbalanced, then that run away climate change would have happened long before man appeared on the scene.
I would still like to know though, if, as Ice core samples suggest, that the earth, from time to time, sees sudden temperature movements (5 degrees C or more) happening in less than a year, and those changes are discrete, then what is the mechanism for this?
Given that the earths atmosphere appears to give us a climate that is stable, can anyone explain how these discrete and sudden changes in temperature come about and appear in our ice cores?
I have only heard one explanation that makes sense, but it is a bit of a far fetched explanation. Can anyone provide me with a better explanation?
stephen richards (05:45:10) :
Or
RealClimate denialism
I did think about it before hitting the spacebar. 😉
The specifics of some of the more advanced discussions on this site are outside of the knowledge or experience of readers like myself. But intuitively, water in its various forms is all about negative feedback. Everyone has had the experience of a sunny day when a cloud comes between you and the sun. The effect is immediate. Cloud cover which persists overnight also seems to help retain regional heat. Here in Western WA, our proximity to the Pacific and persistent cloud cover moderate temperatures, producing (usually) mild winters for our relative latitude. Cylinders of water are sometimes used in passively heated construction to gather daytime sunlight, mitigating heat, then radiating that heat during the evening. Negative feedback seems to be the very reason water makes this planet habitable.
It occurs to me that the overall negative feedback from clouds must be mitigated by oceanic cycles and humidity and wind patterns. Otherwise, an 8W/m2 forcing would keep earth closer to equilibrium and damp the effect of those 30 year cycles to a greater degree.
So much to learn…
This post is entirely correct in flagging up the importance of clouds but I contend that clouds are just one part of a broader negative feedback process controlled by rapid changes in the global air circulation both geographically and in terms of intensity as a result of any extra warming of the air alone (as opposed to extra warming of air and ocean).
Changing ocean surface temperatures induce air circulation changes as the air seeks to restore the sea surface/surface air temperature equilibrium and at the same time resolve ocean induced variations in the sun to sea / air to space equilibrium.
The air circulation changes alter all the processes involved in the rate of energy transfer from surface to space. Cloudiness changes are an inevitable by product of changes in the air circulation systems.
In due course stabilty is always restored between the four said parameters (sea surface / surface air and sun to sea / air to space).
Only huge catastrophic changes capable of altering the temperature of the whole body of the oceans can set a new global equilibrium in the short term (less than millennia). The sun can also do it gradually but it takes centuries e.g. from Roman Warm Period to Mediaeval Warm Period to Little Ice Age to now. The solar effect is heavily modulated over time by ocean cycles. A change in the composition of the air alone cannot do it due to the thermal inertia of the oceans combined with the speed of responses available in the air.
The role of water vapour combined with the latent heats of evaporation and condensation gives the air circulation changes the major part of their ability to accelerate energy transfer from surface to space.
So, the most common and by far the largest forcing at any given time is multi decadal variations in energy emissions from the oceans. In the background are slow century scale changes in solar output.
Temperature changes induced by sun and oceans drive air circulation changes which drive changes in every aspect of climate including convection, conduction, evaporation, condensation, precipitation, windiness, cloudiness, albedo and humidity as regards both quantities and distribution.
Water vapour in itself is not a driver nor does it have cycles or periodicities of it’s own. It’s a very useful contibutor to the whole process though and without it the Earth would be entirely different
Any ocean surface warming is caused by solar energy previously absorbed working it’s way back to the surface. It is becoming clear that oceanic energy emission to the air is not stable on multidecadal time scales.
The air circulation has to balance both the energy flow from ocean to air with the energy flowfrom air to space AND the energy flow from sun to ocean with the energy flow from air to space over time. Everything we observe is a feature of that interplay.
To deal adequately with any warming of the air from extra CO2 or any other increased GHG the air circulation and weather systems just shift their size and/or positions to adjust the rate of energy emission to space to restore equilibrium between air and oceans.
It is the latitudinal position of the weather systems which is most significant in changing the rate of energy flow from surface to space. Secondary to that is the speed of the hydrological cycle.
The equilibrium which the weather systems work back towards is set by the rate of energy flow from the sun modulated by the rate of energy flow through the oceans. It is not set by the characteristics of the air which is the point at which I come to the conclusion that the work of Tyndall and others is faulty.
The air circulation changes ensure that over time the energy radiated to space matches the energy received from the sun despite disruptions in the flow caused by the effects of the ocean cycles or changes in the composition of the air.
Everything we see in the air and the oceans is part of that natural energy balancing interaction and human emissions have no part to play other than a very small insignificant human induced shift in positions or intensities of the main air circulation systems. Wholly imperceptible in the face of natural variability.
The problem with models is that it only uses one given fact and extent that fact further in the future neglecting onther inputs.
Since these papers are 3-4 years old I’m sure climate scientists have had plenty of time to debate the results. Unfortunately, I feel too many of them are wedded to their previous positions and will fight hard to discredit anything that does not match their beliefs.
More and more I’m convinced that climate science is simply too young and naive overall to understand the complexity of nature. These kind of results demonstrate that fact.
I think Stumpy has a point. I am no scientist (ex investment banker…) but I see mean reversion all around me in phenomena where there is volatility (not just in financial markets). Without an in-built mean reversion, things must get out of hand. Even though climate has varied in the past, it still has stayed within a relatively narrow band to allow life to remain on earth. This doesn’t mean there is a guarantee that the earth will always be inhabitable, but if CO2 in the atmosphere has been much higher in some past times and somehow climate didn’t get out of hand. I have not seen scientists make the mean reversion point (or in this case : negative feedback). Did I just miss it ?
Off topic but for those who haven’t seen this news (from the BBC website):
Tim Berners-Lee the inventor of the world wide web has been asked by the British prime minister to help open up access to government data.
“I think there’s a public demand for transparency. This is way beyond party politics and beyond global borders,” Sir Tim said.
He said taxpayers’ money paid for the data so it should be available to them…
… He also explained he had recently given a speech about the subject in California: “I had the audience chanting ‘raw data now!’ about government data. This is an important thing to be involved, independent of the politics of the moment.”
See BBC website http://news.bbc.co.uk/2/hi/technology/8096273.stm
Every day the NWS predicts high 80’s here in Pendleton, Oregon. And every day the thunder clouds swoop it all up into the heavens and we stay cool (and very damp).
Just yesterday we did a post about clouds (http://tinyurl.com/myagqn) and climate models before seeing the new research Steve M. posted at his site. Of course, the “cloud” problem in existing climate models is just one of many. We got an archive of postings on climate model problems here for those interested in that type of article:
http://www.c3headlines.com/climate-models/
C3H Editor
Great article, Anthony. It helps to remind us of the importance of atmospheric circulation on climate. We spend a lot of time here discussing SST’s — ENSO, PDO — but that’s only part of the picture. To keep a balanced perspective here, in my discussions with Bob I’ve pointed out that atmospheric circulation is, according to at least once source, responsible for 50% more poleward transport of heat from the tropics than is ocean currents. Your third image (a cross section of the ITCZ with a cumulonimbus cloud in the center), which is of course a Hadley Cell, is part of that process.
I wonder if there are images, from space, of the ITCZ, during the 1997-98 (or the period leading up to) “Super” El Nino. I would expect this to have been a period during which cloud cover was anomalously weak, leading to much more ocean heating than usual.
> This is particularly true of cumulus and cumulonimbus, which increase with the
> temperature during the day, move huge amounts of energy from the surface aloft,
> reflect huge amounts of energy to space, and fade away and disappear at night.
And what fraction of cloud-cover is due to cumulonimbus? Is it as much as 1%, worldwide?
Yet another classic example of cherrypicking!
REPLY: Oh puhleeeze. No cherrypicking, just using this as an example of negative feedback by clouds. And for ever CB in the ITCZ, there’s about 100 low level cumulus that do the same thing on a smaller scale, adding to that bright reflective band near the equator.
Just look at the top satellite image to see how many CU vs CB there are.
-Anthony