Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. What will Trenberth and Dessler do next? Maybe the editor of Meteorological Applications can be persuaded to commit professional suicide and resign? The key paragraph from the new paper:
…the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.
After all the wailing and gnashing of teeth over the Spencer and Braswell paper in Remote Sensing, and the stunt pulled by its former editor who resigned saying the peer review process failed, another paper was published last week in the journal Meteorological Applications that agrees well with Spencer and Braswell.
This new paper by Richard P. Allan of the University of Reading discovers via a combination of satellite observations and models that the cooling effect of clouds far outweighs the long-wave or “greenhouse” warming effect. While Dessler and Trenberth (among others) claim clouds have an overall positive feedback warming effect upon climate due to the long-wave back-radiation, this new paper shows that clouds have a large net cooling effect by blocking incoming solar radiation and increasing radiative cooling outside the tropics. This is key, because since clouds offer a negative feedback as shown by this paper and Spencer and Braswell plus Lindzen and Choi, it throws a huge monkey wrench in climate model machinery that predict catastrophic levels of positive feedback enhanced global warming due to increased CO2.
The cooling effect is found to be -21 Watts per meter squared, more than 17 times the posited warming effect from a doubling of CO2 concentrations which is calculated to be ~ 1.2 Watts per meter squared. This -21 w/m2 figure from Richard P. Allan is in good agreement with Spencer and Braswell.
[While the -21wm2 and ~1.2 W/m2 values are correct, the comparison is wrong, and it is my mistake. The values are Top of Atmosphere and Surface, which aren’t the same. This prompts a new rule for me, I shall not publish any posts after midnight again (other than something scheduled previously during the day), because clearly I was too tired to recognize this mistake. I’ll add that I have emailed Dr. Allan regarding the question of feedback on hisfigure 7, and have not received a response. – Anthony]
Here’s the paper abstract, links to the full paper (which I located on the author’s website) follow.
Combining satellite data and models to estimate cloud radiative effect at the surface and in the atmosphere
Richard P. Allan
Abstract: Satellite measurements and numerical forecast model reanalysis data are used to compute an updated estimate of the cloud radiative effect on the global multi-annual mean radiative energy budget of the atmosphere and surface. The cloud radiative cooling effect through reflection of short wave radiation dominates over the long wave heating effect, resulting in a net cooling of the climate system of -21 Wm-2. The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of -53 Wm-2. Clouds impact long wave radiation by heating the moist tropical atmosphere (up to around 40 Wm-2 for global annual means) while enhancing the radiative cooling of the atmosphere over other regions, in particular higher latitudes and sub-tropical marine stratocumulus regimes. While clouds act to cool the climate system during the daytime, the cloud greenhouse effect heats the climate system at night. The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed.
1. Introduction
Earth’s radiative energy balance (solar radiative energy absorbed and terrestrial radiation emitted to space) determines current patterns of weather and climate, the complexity of which is illuminated by satellite observations of the evolving distribution and diversity of cloud structures. Representing clouds and the physical processes responsible
for their formation and dissipation is vital in numerical weather and climate prediction, yet many approximations must be made in these detailed models of our atmosphere (e.g. Bony et al., 2006; Allan et al., 2007). Observations of cloud characteristics from satellite instruments and in situ or ground-based measurements are crucial for improving understanding of cloud processes and their impact on Earth’s radiative energy balance (Sohn, 1999; Jensen et al., 2008; Su et al., 2010). The energy exchanges associated with cloud formation and precipitation are also a key component of the global water cycle, of importance for climate change (Trenberth, 2011). In this paper, initially presented at a joint meeting of the Royal Meteorological Society and Institute of Physics on Clouds and Earth’s Radiation Balance (Barber, 2011), the utility of combining weather forecast model output with satellite data in estimating the radiative effect of cloud is highlighted. Using a combination of models and satellite data a simple question is addressed: how do clouds influence the radiative energy balance of the atmosphere and the surface.
As an example of the radiative impact of cloud, Figure 1 displays thermal infra-red and visible channel narrow-band images of the European region from the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) on board the Meteosat-9 satellite (Schmetz et al., 2002).
In both images clouds appear bright: this denotes relatively low infra-red emission to space and relatively high reflection of visible sunlight to space. The hot, generally clear regions of northern Africa are also noticeable in both images since they are associated with substantial thermal emission to space (dark regions in the infra-red image) and high surface reflection from the desert surface (bright in the visible image). The brightest clouds in the thermal image correspond with (1) a trailing cold front extending from the coast of Norway, across Scotland and to the west of Ireland, (2) a developing low pressure system to the west of Iceland, and, (3) a low pressure system in the Mediterranean centred on Sardinia.
These are regions of ascending air with relatively high altitude, low temperature cloud tops which depress the thermal emission to space compared with surrounding regions. These features are also present in the visible image. However, many more cloud structures are also present. There is a prevalence of low altitude cloud over the oceans: this cloud contains large amounts of water droplets which are highly reflective (e.g. Stephens et al., 1978). The imagery captures the complex cellular structure of this cloud (e.g. Jensen et al., 2008) over the region surrounding the Canary Islands. These cloud types are thought to contribute strongly toward uncertainty in climate projections (Bony et al., 2006). While these clouds also strongly attenuate infra-red radiation, their impact on the thermal radiation escaping to space is modest since cloud-top temperatures are not dissimilar to the surface at night and so they do not contribute significantly to the strong natural greenhouse effect of the clear-sky atmosphere.
The altitude and optical thickness of cloud determines the overall radiative impact of cloud, a combination of the warming greenhouse effect and the surface-cooling solar
shading effect. Yet, probably an even stronger influence does not relate to the cloud itself. The time of day and time of year dictate the incident solar radiation and, therefore,
modulates the strength of the short wave reflection: clearly at night the solar influence of cloud is absent.
…
7. Conclusions
Exploiting satellite measurements and combining them with NWP models initialized through assimilation of available observations enables the effect of clouds on the Earth’s radiative energy balance at the surface and within the atmosphere to be quantified for the present day climate. Consistent with previous results (Ramanathan et al., 1989; Su et al., 2010), the cloud radiative cooling effect through reflection of short wave radiation is found
to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.
The short wave radiative effect of cloud is primarily manifest as a reduction in the solar radiation absorbed at the surface of −53 Wm−2 for the global multi-annual mean. The magnitude of this effect is strongly modulated by the incoming solar radiation and the dominance of cloud short wave cooling over long wave greenhouse trapping is maximum around local noon (Nowicki and Merchant, 2004) while the cloud long wave heating effect dominates at night.
The long wave greenhouse effect of cloud measured at the top of the atmosphere is manifest primarily as a heating of the atmosphere in the moist tropics, consistent with calculations by Sohn (1999).
Over the marine stratocumulus regions and across higher latitudes the cloud-base emission to the surface becomes substantial and dominates over the reduced outgoing long wave radiation to space resulting in enhanced radiative cooling of the atmosphere and heating of the surface. The cloud radiative influence on the exchange of radiative fluxes between the atmosphere and the surface are intimately linked with the water cycle through radiativeconvective balance. While tropical, high-altitude clouds act to stabilize the atmospheric profile radiatively, clouds over polar regions tend to cool the atmosphere while heating the surface through enhanced atmospheric longwave radiative emission to the surface. In future work it would be informative to categorize these effects by cloud type further (e.g. Futyan et al., 2005) and compare with climate model simulations. These analyses are vital in constraining cloud feedback processes further and in linking to future changes in the water cycle (Stephens, 2005; Bony et al., 2006; John et al., 2009).
A particular challenge is the accurate quantification of surface radiative fluxes due to the sparse ground-based observing network (Roesch et al., 2011) and also monitoring current changes in cloud radiative effect in satellite data, reanalyses and models (Wielicki et al., 2002); combining meteorological reanalyses with satellite data and surface observations provide a vital methodology for meeting these challenges.
Abstract is here: http://onlinelibrary.wiley.com/doi/10.1002/met.285/abstract
Full paper is here: http://www.met.reading.ac.uk/~sgs02rpa/PAPERS/Allan11MA.pdf
UPDATE: Some people in comments including Dr. Roy Spencer, (and as I was writing this, Dr. Richard Allan) suggest that the paper isn’t about feedback (at least in the eyes of IPCC interpretations, but Spencer adds “it could be”). Thus I’ve removed the word from the headline to satisfy such complaints. My view is that clouds are both a feedback and a forcing. Others disagree. That’s an issue that will occupy us all for sometime I’m sure.
Regarding cloud feedbacks, here’s what I noted in the paper in section 6, near the end. Allan is referring to figure 7 which shows (a) net radiation and (b) net cloud radiative forcing:
Substantial negative anomalies in net radiative flux from ERA Interim are apparent in 1998 and 2010, both El Niño years, suggesting that the substantial re-organization of atmospheric and oceanic circulation systems act to remove energy from Earth during these periods.
You can clearly see the famous double peak in the 1998 El Niño, but it is inverted. To me that looks like a thermostat action, and not one with stuck electrical contacts, i.e. a negative feedback. I’ve also updated the text related to the incorrect comparison I made. – Anthony
You are confusing forcing with feedbacks.
Oh dear indeed.
“If this were true then when the clouds covered the sun you would feel colder…oh, hang on a minute…”
And cloudy nights would feel colder than clear nights …. oh!
An interesting site – always nice to have additional view-points and information and an ability to partake in open discourse.
Thanks, cheers…
The link at the end of the “[t]his -21 w/m2 figure from Richard P. Allan is in good agreement with Spencer and Braswell” sentence goes to an article about Dessler instead. — John M Reynolds
James said, ‘And cloudy nights would feel colder than clear nights….oh!’
But there is no sun at night so no heat source for the clouds to block.
I think you’ve jumped the gun on this. The -21 W/m^2 is not feedback — which would typically be in the units of W/m^2/K — but the overall effect of clouds. In a quick scan of the paper, it appears that they didn’t find much of a trend in radiative forcing due to clouds over the period studies — but a back-of-the-envelope estimate of the size of any expected trend over that period (due to feedback) would be small and probably not discernible within the noisiness of their charts.
They do say this: “Substantial negative anomalies in net radiative flux from ERA Interim are apparent in 1998 and 2010, both El Ni˜no years, suggesting that the substantial re-organization of atmospheric and oceanic circulation systems act to remove energy from Earth during these periods.”
James says:
September 20, 2011 at 4:03 am
Did you forget that the sun doesn’t shine at night?
Duh!
Re: Apples and Pears: Spencer (and Dessler as well) are interested in the feedbacks between clouds and temperatures. Allan (so far) doesn’t care too much for temperature or feedbacks. He just updates some (two) of the numbers in Trenberth’s “global annual mean Earth’s energy budget”. For example, his net cooling effect is 8 W/m² larger than the one in table 3.1 of the IPCC-FAR in 1990.
John Marshall says:
“So science agreeing with observation that a cloudy day is cooler than a sunny one”
and a cloudy night is warmer then a clear sky night.
.
Ah clouds, too nebulous and foggy for the absolutists to comprehend…
This paper does not appear to say what is claimed by Mr. Watts. That is, the -21 W/m2 is a mean net forcing “for the present day climate” (as the paper says.) By contrast, the cloud feedback effect under discussion by Dessler and Spencer (among others) has to do with changing radiative forcings and how cloud would respond. “Feedback diagnosis” (to use Spencer’s term) is challenging because–as this paper notes–the most direct ways of figuring out how clouds affect must immediately confront the diversity of cloud types, locations, and even times, all of which affect the clouds’ net effect.
Note that the paper says that its results are “Consistent with previous results (Ramanathan et al., 1989; Su et al., 2010).” Don’t know about Su et al., but Ramanathan is AGW mainstream as you can get. And I note, too, that one of the most iconic images in climate science (the Kiehl-Trenberth-Fasullo energy budget diagram) gives the shortwave forcing of clouds as -79 W/m2–so (amazing, isn’t it?) climate science has not hitherto neglected the cooling effect of daytime cloud–contrary to what some commenters above have allowed themselves to believe.
Bart is correct. This paper is not about cloud feedback…it is about the average effect of clouds on the climate system, which the IPCC, Trenberth, Dessler, et al. will all agree is a cooling effect. It is an update of the early estimates from ERBE many years ago.
Feedback is instead how clouds will change in response to a temperature *change* from the average climate state.
Now, it might well be that since the average effect of clouds on the climate system in response to radiative heating by the sun is to cool the Earth, then a small increment in radiative heating (e.g. from more CO2) will ALSO result in clouds having a further increment in cooling. That’s basically what Monckton has been claiming, and he might well be correct. Lindzen pointed this out also in his 1990 BAMS paper.
I just wanted to point out that the IPCC view is that this paper is not about cloud feedback….even though it might be about cloud feedback. 😉
REPLY: Thanks Roy for the clarification. The question of whether clouds act as feedback, forcing, or both is one that will occupy us as a while. My interpretation is as both, they act as a forcing (albedo) and as a feedback via the water vapor cycle, see Willis: Further Evidence for my Thunderstorm Thermostat Hypothesis
See the update I’ve posted.
– Anthony
James:
In the full paper, Allan states that clouds will warm nights, although it will cool days.
If the calculations are verified, it’s good news for climate. But I don’t see that it challenges any prevailing understanding: The fact that clouds reflect sunlight although they hold in infrared is well known, and is why the magnitude and even the sign of the cloud feedback has been allocated a high degree of uncertainty. It will be interesting to see the reaction in the literature: Whether it enables the models to home in on a more restricted range of parameters.
Just to clarify a point on the cause/effect issue.
My view is that latitudinal air mass shifting (and thus cloudiuness and albedo changes on a global scale) will occur from either or both of:
i) A top down change in solar activity altering the vertical temperature profile of the upper atmosphere above the tropopause.
ii) A bottom up change in the rate at which oceans release energy to the air altering the temperature differential between surface and tropopause.
In practice both effects are competing with one another all the time with the latitudinal shift constantly adjusting to maintain the overall energy budget by changing the speed of the water cycle. That shifting is always a negative system response.
In consequence it will be very hard to separate cause and effect as regards cloudiness and albedo changes.
Solar influences will disguise oceanic effects and vice versa.
However I would suggest that overall the cloudiness changes are a result of latitudinal shifts and those shifts arise from the combined net effect on the energy budget from the solar and oceanic forces.
Poleward shifts cause decreasing cloudiness overall by widening the equatorial high pressure cells either side of the ITCZ and thereby increasing the speed of the water cycle globally.
Equatorward shifts cause increasing cloudiness overall so that the equatorial high pressure cells shrink thereby decreasing the speed of the water cycle globally.
That is clearly the opposite of initial expectations because one would normally anticipate that a faster water cycle would involve more clouds but that appears not to be the case due to the latitudinal shifting.
I think the best way to explain it is to point out that when the jets are more poleward they become more zonal with a greater temperature contrast between polar and equatorial air masses and more vigour in the zonal flow. That increased vigour increases the speed of the water cycle by more than the reduced cloudiness decreases it. In effect the faster water cycle is concentrated into smaller areas.
In contrast when the jets are more equatorward they become more meridional with a reduced temperature contrast between polar and equatorial air masses for less vigour in the zonal flow. Thus one then sees a slower water cycle but more clouds overall for the opposite effect.
That results in a faster water cycle offsetting warming from whatever cause and a slower water cycle trying to reduce energy loss offsetting cooling from any cause (but only temporarily because energy reflected never gets into the system in the first place).
Phil Clarke says “Oh dear indeed” … in regard to confusing forcing and feedbacks. That one of the best under-statements one could possibly respond with!
Set that against the original post’s language which starts with “Oh dear …” and then goes on to say:
“… can be persuaded to commit professional suicide and resign?”
“… all the wailing and gnashing of teeth …”
“… the stunt pulled …”
“… machinery that predict catastrophic levels of positive feedback …”
The gentle contrast with error illumination is splendid.
REPLY: What I think is splendid is figure 7, which shows an elegant relationship, have a look. Show me where there’s positive feedback demonstrated there and the next time I’m in the UK I’ll look you up and buy you a beer. – Anthony
@James Baldwin,
I didn’t know anyone was proposing that the Earth got warmed by the Sun at night.
When the clouds are gone at night I also notice that the CO2 doesn’t seem very effective at keeping the warmth in. I know, it is just obvious, but to conclude the obvious, In the daytime clouds keep more heat out and at night they keep more heat in – can I have a Ph.D now?
Phil and James,
So it seems CO2 can tell the time as well now, only producing clouds at night and not during the day?
Did I get that right?
Well, I guess we all knew cloudy days are cooler and cloudy nights are warmer, but now that has been quantified. An important step in determining whether these values change in response to some stimuli like cosmic rays or temperature.
If you look at figures 3 and 4 in the paper you’ll see the equator very pronouncedly negative, I wonder if this is Willis’ thermostat in action.
Those saying that this paper is not addressing the feedback issue may be missing the point. For the strongly positive water vapour feedback demanded by the IPCCs doom scenarios to work, the increased evaporation would need to be prevented from causing more clouds. This is not plausible in an atmosphere with a vertical pressure gradient.
Bart Verheggen says:
September 20, 2011 at 3:59 am
As the overall climate warms, cloud cover will increase (the earth has a surface disproportionately covered in water, which rate of evaporation is proportional to the temperature). As the overall climate cools, cloud cover will decrease (the oceans provide less moisture to the air, hence less source for clouds).
Are you saying the earth will have more clouds with less atmospheric moisture? That’s an illogical conclusion. More clouds–more radiative effect; less clouds–less radiative effect (daytime radiative impact far exceeds that at night). It’s a self modulating system that can easily dissipate any additional heat man’s activities may generate.
lol, out with the forcing/feedback meme. Predictable, is suppose. One step at a time I suppose.
Ladies, we’re told CO2 provides extra warming, causing climate change. You can call it a forcing if you desire, but its really a feedback in the truest sense in a few different perspectives. Now, we’re learning clouds have a cooling effect. You can call it a feedback if you wish. The point is, I no of no model that properly accounts for the cooling the clouds provide. But, that’s not the interesting point. What will be interesting is to watch the warmista contort themselves trying to explain how warming won’t increase cloud cover. Then tell us how that wont cool the planet. Then explain again what a forcing is. Symantics, I love that part of the debate. phhtt.
Anthony, your link that states, “…..in good agreement with Spencer and Braswell. Here’s….” provides a link to some Dessler ramblings, here. http://www.sciencedaily.com/releases/2010/12/101209141231.htm I could be wrong, but I don’t believe that’s what you wanted to show when one would click on the link.
Bart Verheggen says: (September 20, 2011 at 3:59 am)
“Anthony,
Could you please point out where in this paper it is mentioned that “clouds have large negative-*feedback* cooling effect on Earth’s radiation budget”?
I may be wrong, but I think you’re confusing two issues:
– the net effect of clouds on climate
– the net feedback of clouds on a change in climate
The paper, as I read it with a first quick overview, addresses the first, whereas you interpret it as if it addresses the second. ”
From the abstract: “The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed.”
Perhaps I read that incorrectly.
Oh dear, I think this is really going to cloud the issue…
Sorry could.. not… resist….
Bart Verheggen says:
September 20, 2011 at 3:59 am
I may be wrong, but I think you’re confusing two issues:
– the net effect of clouds on climate
– the net feedback of clouds on a change in climate
The paper, as I read it with a first quick overview, addresses the first, whereas you interpret it as if it addresses the second.
They are two distinctly different issues. The second (clouds as feedback) is about how cloud cover and properties might change in response to a warming or cooling of the climate: Will the net cloud radiative effect become more or less negative.
Bart, put down that goalpost and do some thinking.
http://tallbloke.wordpress.com/2011/09/17/cloud-albedo-what-does-it-respond-to
Verheggen: “Will the net cloud radiative effect become more or less negative”
Thought you and your compadres knew?