Guest Post by Willis Eschenbach
I’ve been investigating one of my favorite datasets in the last few days, the CERES satellite-based top-of-atmosphere (TOA) radiation dataset. In particular, I’ve taken month-by-month global and hemispheric averages of the data. The dataset consists of observations of three variables—downwelling solar radiation, upwelling longwave (infrared) radiation, and upwelling shortwave radiation (reflected sunlight). From these I derive a further dataset. This is the top-of-atmosphere (TOA) imbalance. It is calculated as downwelling solar minus upwelling (reflected) solar minus upwelling longwave. That gives a fascinating look at the overall radiation picture.
I got to thinking about this because of a curious claim in a recent paper published in Nature Climate Change entitled Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods (paywalled). I did love the whole concept of “model-based evidence”, but that wasn’t what caught my eye. It was this statement (emphasis mine):
There have been decades, such as 2000–2009, when the observed globally averaged surface-temperature time series shows little increase or even a slightly negative trend (a hiatus period). However, the observed energy imbalance at the top-of-atmosphere for this recent decade indicates that a net energy flux into the climate system of about 1 W m−2 (refs 2, 3) should be producing warming somewhere in the system (refs 4, 5). Here we analyse twenty-first-century climate-model simulations that maintain a consistent radiative imbalance at the top-of-atmosphere of about 1 W m−2 as observed for the past decade. [References are listed at the bottom of this post.]
Anyhow, here’s some news regarding that claim of a consistent TOA imbalance, from the CERES satellite dataset:
Figure 1. CERES satellite-measured top-of-atmosphere (TOA) radiation levels, starting in January 2001. Numbers on the horizontal axis are months. Shown are the solar energy entering the system (red line), solar energy leaving the system (dark blue line) and longwave (infrared) energy leaving the system (light blue line). The overall monthly imbalance at the TOA is shown at the bottom in purple. The 12-month running average for each variable is shown as a thin line. Curiously, the variations in upwelling longwave are about 6 months out of phase with the downwelling radiation. All radiation values are positive. TOA Imbalance is solar less reflected solar less outgoing longwave, i.e. inflow less outflow. Twelve-month averages vary too little for the changes to be visible at this scale.
Now, there are a number of things of interest in this chart. The first is the fact that while the seasonal variations are fairly large, tens of watts per square metre, the annual variations are so small. At this scale we can hardly see them. So let’s expand the scale, and take a more close-up look at just the variations in the overall TOA energy imbalance (purple line at bottom of Figure 1). Figure 2 shows that result.
Figure 2. Closeup of the overall energy imbalance. Horizontal scale is months. Narrow line shows running centered 12-month averages of the TOA imbalance data. All radiation values are positive. TOA Imbalance is solar less reflected solar less outgoing longwave, i.e. inflow less outflow.
Here, we can begin to see the small variations in the 12-month running average. However, the average itself is around five watts per square metre … not good. That much out of balance is not credible.
This shows the difference between precision and accuracy. You see that the measurements are obviously quite precise—the 12-month running average only varies by about three-quarters of a degree over the whole period.
However, in absolute terms they’re not that accurate, we know that because they don’t balance … and it’s very doubtful that the earth is out of balance by five watts per square metre. That’s a very large amount, it would be noticed.
Now, I’ve previously discussed how James Hansen deals with this problem. He says:
The precision achieved by the most advanced generation of radiation budget satellites is indicated by the planetary energy imbalance measured by the ongoing CERES (Clouds and the Earth’s Radiant Energy System) instrument (Loeb et al., 2009), which finds a measured 5-year-mean imbalance of 6.5 W/m2 (Loeb et al., 2009). Because this result is implausible, instrumentation calibration factors were introduced to reduce the imbalance to the imbalance suggested by climate models, 0.85 W/m2 (Loeb et al., 2009).
As a result, Hansen used the Levitus data rather than the CERES data to support the claims of a ~ one watt per square metre radiation imbalance. However, all is not lost. The precision of the CERES data very good. In Figure 2 we can see, for example, how one year’s TOA radiation imbalance is different from another. So let’s expand the scale once again, and take an even closer look at just the 12-month running averages, for all four of the radiation measurements shown in Figure 1.
Figure 3. An even closer look, this time at just the tiny variations in the 12-month running averages of the CERES data as shown in Figure 1. All radiation values are positive. TOA Imbalance is solar less reflected solar less outgoing longwave.
Now we’re getting somewhere.
The first thing I noticed is the precision of the measurements of the downwelling solar radiation (red line). As you might expect, the sun is quite stable, it doesn’t vary much compared to the variations in reflected solar and upwelling longwave radiation. And the observations reflect that faithfully. So it seems clear that their instruments for measuring radiation are quite precise.
Next, I noticed that the change in the imbalance (purple) is more related to the change in reflected solar (dark blue) than to the variations in upwelling longwave. I’ve highlighted the reflected solar (dark blue) in the graph above. This is confirmed by the correlation. The R^2 between TOA imbalance and reflected solar is 0.67; but between TOA imbalance and upwelling longwave, R^2 is only 0.07.
This seems like an important finding, that the imbalance is mostly albedo related, and that because of variation in the albedo, the variations in the reflected solar energy were on the order of ± three tenths of a watt within a few years.
Finally, I am once again surprised by the overall stability of the system. Twelve-month averages of all three of the variables (the TOA balance, reflected solar, and upwelling longwave) are all stable to within about ± 0.3 watts per square metre. Out of a total of 340 watts per square metre going each way, that’s plus or minus a tenth of one percent … I call that extremely stable. Yes, with a longer sample size we’d likely see greater swings, but still, that’s very stable.
And that brings me back to the quotation from the paper where I started this post. They say that there is
… a consistent radiative imbalance at the top-of-atmosphere of about 1 W m−2 as observed for the past decade …
Now, according to their references [2] and [3], this claim is based on the idea that the excess energy is being soaked up by the ocean. And this claim has been repeated widely. I’ve discussed these claims here. The claims are all based on the Levitus ocean temperature data, which shows increasing heat in the ocean. Here’s my graph of the annual forcing needed to give the changes shown by Levitus in ocean heat content:
Figure 4. Annual forcing in watts per square metre needed to account for the energy going into or coming out of the ocean in the Levitus data. Data is for the top 2,000 metres of water. Note that despite average values being used, both by Hansen and also in the study under discussion, neither the mean nor the trend are statistically significant. Further discussion here.
For current purposes, let me point out that Figure 4 shows that in order for the ocean to gain or lose the energy that is shown in the Levitus data, it requires a very large year to year change in the amount of energy entering the ocean. That energy has to come from somewhere, and it has to go to somewhere when it leaves the ocean. Since the solar input is about constant over the period, that energy has to be coming from a change in either the upwelling longwave or the reflected solar … and we have precise (although perhaps inaccurate) data from CERES on those. Fortunately, the lack of accuracy doesn’t matter in this case, because we’re interested in the year to year changes. For that all we need is precision, and the CERES data is very precise.
So … let me compare the forcing shown by the Levitus ocean heat content in Figure 4, with the CERES data. Figure 5 shows the difference.
Figure 5. Forcing given by the Levitus ocean heat content data, compared to the CERES data shown in Figure 3.
As you can see, they have a couple of big problems with their claims of a consistent 1 W/m2 imbalance over the last decade.
First, it is contradicted by the very data that they claim establishes it. There is nothing “consistent” about what is shown by the Levitus data, unless you take a long-term average.
The second problem is with the Levitus data itself … where is the energy coming from or going to? While the CERES TOA imbalance is not accurate, it is very precise, and it would certainly show a fluctuation of the magnitude shown in the Levitus data. If that much energy were actually entering or leaving the ocean, the CERES satellite would surely have picked it up … so where is it?
I’ve discussed what I see as unrealistic error bars in the Levitus data here. My current comparison of Levitus with the CERES data does nothing to change my previous conclusion—the precision of the Levitus data is greatly overestimated.
Finally, the idea that we have sufficiently accurate, precise, and complete observations to determine the TOA imbalance to be e.g. 0.85 watts per square meter is … well, I’ll call it premature and mathematically optimistic. We simply do not have the data to determine the Earth’s energy balance to an accuracy of ± one watt per square metre, either from the ocean or from the satellites.
Best regards to all,
w.
MY OTHER POSTS ON THE CERES DATA:
Observations on CERES TOA forcing versus temperature
Time Lags In The Climate System
A Demonstration of Negative Climate Sensitivity
DATA:
CERES data: Unfortunately, when I go to verify it’s still available, I get:
The Atmospheric Science Data Center recently completed a site wide redesign.
It is possible that the page you are looking for is being transitioned. Please try back later.
If the page you have requested is still not available, it may have been renamed or deleted.
It is recommended that you use the Search interface on the ASDC Web Site to find the information you were looking for.
Since I got there via the aforementioned “Search interface on the ASDC Web Site”, I fear we’re temporarily out of luck.
[UPDATED TO ADD] I’ve collated the global and hemispheric monthly averages from R into a “.csv” (comma separated values) Excel file available here.
REFERENCES FOR THE NATURE CLIMATE CHANGE ARTICLE:
2. Hansen, J. et al. Earth’s energy imbalance: Confirmation and implications.
Science 308, 14311435 (2005).
3. Trenberth, K. E., Fasullo, J. T. & Kiehl, J. Earth’s global energy budget.
Bull. Am. Meteorol. Soc. 90, 311323 (2009).
4. Trenberth, K. E. An imperative for climate change planning: Tracking Earth’s
global energy. Curr. Opin. Environ. Sustain. 1, 1927 (2009).
5. Trenberth, K. E. & Fasullo, J. T. Tracking Earth’s energy. Science 328,
316317 (2010).
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Willis, back in ’07 I was doing work with the public version of the CERES data, and had to develop a method to “demodulate” the color graphics into real numbers, to obtain an overall average outflow, inflow, etc. I did, after a months struggle. I noted 3 watt to 10 watt net inward as a typical value, month to month. At first I had my “polarities” reversed, and I thought it was major “global cooling” going on, and was wondering what massive conspiracy had it being ignored.
Thanks to the kind interface with Dr. Spencer, I got “turned around” and found it was a 3 to 10 watt per square meter INWARD flux (net). Of course, I was concerned: This would mean AWG was real and substantial. I woefully admitted my agony to Dr. Spencer, and he quickly sent me some papers and info, and noted the “baseline calibration problem”. Saying something like, “The CERES data set is good for ‘trends’ and relative comparisons, but CANNOT and SHOULD NOT be used as an “absolute value” at this point.”
I’m pleased that that conclusion has NOT changed, and that you have found “the usual suspects” vainly trying to make a “silk purse out of a sow’s ear”. (Isn’t that and amazing ancient reference to a problem which still persists?)
Max
Randall Harris says:
August 30, 2013 at 10:48 am
You’re in luck Randall–since the “heat” is fudged, you can fudge any explanation you want.
There’s nothing easier than a good fantasy.
I love the way Willis makes sense of stuff, cheers.
george e. smith says:
August 30, 2013 at 1:40 pm
Not sure what your point is here, george. While I’d love to have 2-minute measurements for the whole world, we don’t have that. Instead, we have what the satellite measures when it flies over. Sometimes it is 1362 W/m2 … and sometimes it’s half that and sometimes it is zero.
Now, if you don’t want to use averages, then you are in the wrong field of science—climate is defined as the average of weather.
So just what would you suggest I do?
w.
What I am sure is a daft question, but how do we know the m/2 at the TOA?
IIRC the TOA height/diameter/m/2 is not a constant either globally or hemispheric (season)? So how do we account for such changes? Are we sure we know what m/2 we are relating energy inputs/outputs to?
YesWillis, the was my point. Thanks for clarifying it.
George E. Smith, is this you?
http://en.wikipedia.org/wiki/George_E._Smith
Willis Eschenbach says:
August 30, 2013 at 12:42 pm
Lester Via says:
August 30, 2013 at 11:09 am
What about the radiant energy that is converted to chemical energy by photosynthesis. If that
exceeds the heat energy released by both burning fuels and the slow oxidation of decaying plant life, couldn’t that be responsible for at least part of hidden energy?
Actually, the best you can do is break even, it all goes back to heat. Solar electromagnetic radiation is converted into a variety of forms of energy—chemical (via photosynthesis), thermal (via absorption), latent (via evapotranspiration), mechanical (via motion of wind and oceans).
At the end of the day, however, it all turns back into heat. The only question is, how long is “the day”? If the wind blows sand up onto a high ledge, it could sit there for a thousand years. Once it falls back down to the ground, however, the stored potential energy is turned back into heat.
For organic materials, the process is generally faster. When a plant is eaten by a deer, it is turned into heat to keep the deer warm, plus mechanical energy moving the deer around … and the mechanical energy of course quickly turns into heat.
“How long is the day?” is a really intriguing question. When you reckon that at least most oil and certainly all coal are in fact only now seeing the next dawn, that “day” can be 10s or 100s of millions of years in length. If most photosynthesis goes on in the oceans, then a lot of sunlight is falling to the ocean floors as organic ooze and staying there. I doubt it would account for much of the imbalance you outline so elegantly though. Great read.
GE Smith: “They say climate is the average of weather; it isn’t, it’s the long term integral of the weather”
That is a very good way of expressing it. I did not realise that was what you meant by your earlier statement.
Now how does that relate to Willis’ TOA data. How should this be done in the context of what you are saying?
Ref: Fig 3
I’d expect reflected solar and upwelling longwave to be negatively correlated for obvious reasons, but eyeballing the graph, they look to be positively correlated. Is this an orbital effect or what?
Don K “The Aqua satellite — which is one of the CERES platforms — seems to be in a 98 degree orbit (82N to 82S) at about 600km altitude. I would guess that they do something special during the short periods when the satellite is directly between the sun and the Earth’s surface. ”
Thanks Don. So that orbit with essentially downward looking instrumentation means that it will NEVER measure surface reflection from low incident angles. It is not correctly measuring reflected SW and therefore will produce a net warming imbalance.
Roy Spencer is quoted above as saying it is only suitable for measuring trends etc. but even that is thus in doubt. The effect of the larger annual swing and lower minimum of Arctic ice coverage will not be correctly assessed as the level (and hence the change) in direct reflection is not even measured. Only conditions showing diffuse reflection are measured.
Sea water that would normally absorb almost all incoming solar will reflect as much as 90% at angles of incidence less than 10 degrees: conditions that can be found in polar regions for several months of the year.
An estimate of the fuel value of an acre of biomass can be found at http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/21_2_NEW%20YORK_04-76_0021.pdf.
Using their annual yield estimate of 450 million BTUs per acre one can estimate the solar energy that has been sequestered by the biomass and, consequently cannot show up as upwelled radiation.
450 million BTUs per acre corresponds to 111,193 BTU per square meter or 117 megajoules per square meter. Assuming a growing period of 6 months this equates to an average power of 7.5 Joules per second per square meter or 7.5 watts per square meter. Unless I have miscalculated (certainly won’t be the first time) this is in the ballpark of the missing energy – at least over land areas.
Although, as Willis explained earlier, all the sequestered energy will eventually show up as heat when released, but, as in most agricultural crops, that will not happen the same place the energy sequester took place but is likely be released in a highly populated area – such as an Urban Heat Island. What will that do to the methods being used by those attempting to account for the missing energy?
Philip Bradley says:
August 30, 2013 at 3:54 pm
Ref: Fig 3
I’d expect reflected solar and upwelling longwave to be negatively correlated for obvious reasons, but eyeballing the graph, they look to be positively correlated. Is this an orbital effect or what?
==========
If you said explicitly what you regard as “obvious” someone may be able to explain your paradox. This has already been discussed to some extent.
Another excellent piece of lateral thinking, Willis. That said, I’m kind of with Lester Via and Mark Bofill with regards to the extra energy.
According to other satellites, the Earth’s vegetative matter has increased by 6% since satellite records began. When trees die off they don’t break down immediately and release their trapped energy, which is how dendrochronologists are able to go back thousands of years with measurements. We have Carbon Dioxide mixing with Calcium Carbonate in oceans and forming limestone which could last millions of years.
80% of all living matter is said to be bacteria. Although the bacteria itself wouldn’t last very long, what it leaves behind could very well last a long time. Given all the living “stuff” on Earth, I’m kind of surprised it only takes 5W/m^2 to sustain it all.
Solar reflection is mostly due to clouds, and while clouds vary in their reflectivity, clouds that reflect incoming solar upward will also reflect outgoing LWR downward.
I may be re-asking one of rgb’s kaleidoscope of questions. Are we measuring only the vertical movement of energy in and out? The sun’s energy at low angles to the sphere of the TOA would result in some reflection away from the instrument that would go unnoticed and similarly higher reflection in higher latitudes of the surface of the planet and the cloud surfaces. In essence this translates into a smaller effective disk area receiving the energy than the pi(radius)^2 of the earth that we “spread” the incoming solar over. If this is correct, I don’t find 6 or 7 watts/m^2 imbalance such a surprise.
Willis,
Very nice post. Informative and clear. Thanks.
@Willis, and Aphan –
Question: is there significant variability in heat transfer from the earth’s interior? Otherwise, am I assuming correctly that in any case, regardless of the observed range of variability (if it obtains at all), that it cannot have a detectable effect on ocean temps? It’s my (limited) understanding that heat moves within the Earth’s mantle, which is of a plastic consistency, not rigidly solid, by convection.
george e. smith says:
August 30, 2013 at 1:40 pm
They say climate is the average of weather; it isn’t, it’s the long term integral of the weather, ….
So George, describe the climate outside your window right now, without using any weather terms.
Just kidding! Last thing I would ever do is disagree with you. You are far more intelligent, experienced/knowledgeable in math and practiced in the “climate” arts than I am. However, logically your above statement lacks completeness and THAT is typically … what is wrong with “Climate Science”.
Of course, climate is the whole of weather over space and (as you said) time. But space (or defined area) cannot be left out. And no, of course you cannot “average” the whole of weather into climate. The components of weather are – diverse, different – whatever term you want to use. For example, you cannot “average” temperature and humidity together. It would make any sense. That’s the fallacy of “global” climate. It doesn’t exist except in some imaginary sense. No one can describe it without “averaging” one or more components of weather.
But quite often, if not all the time, “Climate Change” is defined/promoted by the AGW crowd as a negative change in “the average” of a single component of weather! (or it is used as proof of climate change.) That is another thing that is wrong with climate science. “They” average some components of “current” weather (ignoring a lot of others) then compare it to the “modeled” average (or the average of some antiquated records) of the same components at an earlier time and call it – “Climate Change” when they don’t match.
So the first thing one should do when entering into a discussion about “climate” is get clarity on exactly what climate (or the whole of weather over what time and what space) is or isn’t. (At least for that particular discussion.) But whatever one agrees climate is, it still must be the average of the components of the integral, because it is – over some time, no matter how short, and some space, no matter how small. Or it isn’t climate, it’s just – weather. And we know the components of weather over a particular space are subject to change – over time. And the only way to describe the “climate” over that space, is to……….. 🙂
Willis, as always, a thought provoking post. Good discussion in the comments. As usual I continue to add to my vast wealth of useless (unmarketable) knowledge. 😉
Mark Harvey aka imarcus says: @ur momisugly August 30, 2013 at 12:50 pm
…for a concise explanation, refer to John Kehr’s book An Inconvenient Skeptic….
>>>>>>>>>>>>>>>>>>>>>
John Kehr came to mind as soon as I started reading this thread. As an engineer he makes a lots of sense and has a gift for explaining things. I would suggest:
The Earth’s Energy Balance: Simple Overview (It deals with Trenbreth’s Energy Cartoon)
The Difference between “Forcing” and Heat Transfer
Temperature Dependence of the Earth’s Outgoing Energy
And these background articles:
Part 1: Radiative Heat Transfer – Overview
Part 2: Radiative Heat Transfer – Medium 1/2
Part 3: Radiative Heat Transfer – Medium 2/2
Misunderstanding of the Global Temperature Anomaly
The illustrations for his book are:
Chapters 1-3
Chapters 4-5
Chapters 6-7
Chapters 8-10
Chapter 11
Chapter 12: The Earth’s Atmosphere
Chapters 13-14
Even if you do not read his book they are certainly worth looking at.
Willis Eschenbach says:
August 30, 2013 at 12:24 pm
“So even on the timescales of oceanic overturning, which are one or a few thousands of years, geological heat is a third-order effect. That’s why although it is real, it is usually ignored in discussions of the climate fluctuations.”
have you ever seen this paper
http://www.ocean-sci.net/5/203/2009/os-5-203-2009.pdf
Geothermal heating, diapycnal mixing and the abyssal circulation
J. Emile-Geay1 and G. Madec2,
Abstract. The dynamical role of geothermal heating in abyssal circulation is reconsidered using three independent arguments. First, we show that a uniform geothermal heat flux close to the observed average (86.4 mW m−2) supplies as much heat to near-bottom water as a diapycnal mixing rate of ∼10−4 m2s−1 – the canonical value thought to be responsible for the magnitude of the present-day abyssal circulation. This parity raises the possibility that geothermal
heating could have a dynamical impact of the same order….
….For strong vertical mixing rates, geothermal heating enhances the AABW cell by about 15% (2.5Sv) and heats up the last 2000 m by ∼0.15◦C,reaching a maximum of by 0.3◦C in the deep North Pacific. Prescribing a realistic spatial distribution of the heat flux acts to enhance this temperature rise at mid-depth and reduce it at great depth, producing a more modest increase in overturning than in the uniform case. In all cases, however, poleward heat transport increases by ∼10% in the Southern Ocean. The three approaches converge to the conclusion that geothermal
heating is an important actor of abyssal dynamics, and should no longer be neglected in oceanographic studies…”
Willis will you post your “R” data, R code and any CRAN packages you use?
Philip Bradley says:
Solar reflection is mostly due to clouds, and while clouds vary in their reflectivity, clouds that reflect incoming solar upward will also reflect outgoing LWR downward.
===
Then it probably matters where the clouds are. Majority of solar comes into the tropics and is unidirectional. Out-going happens everywhere and it covers 4 pi steradians.
Tropics don’t have winter.
The initially ‘odd’ phase relationship is probably a reflection of N/S land ration and perihelion = NH winter.
I have not tested with numbers but my reading of phase in the graph did not make it seem paradoxical.
paulhan says:
August 30, 2013 at 4:21 pm
well, I was toying with the idea, but the trouble is I don’t think the numbers add up.
How many watts over the entire surface of the earth per year? I thought 10^17ish earlier but I think I made an error and that’s too low. But even if that’s right, if cyanobacteria stores 450 TW and phytoplankton stores 63 TW, we aren’t in the ballpark by a couple of orders of magnitude.
Still, I could be wrong, I often am. 🙂