From the Massachusetts Institute of Technology
The missing piece of the climate puzzle
In classrooms and everyday conversation, explanations of global warming hinge on the greenhouse gas effect. In short, climate depends on the balance between two different kinds of radiation: The Earth absorbs incoming visible light from the sun, called “shortwave radiation,” and emits infrared light, or “longwave radiation,” into space.
Upsetting that energy balance are rising levels of greenhouse gases, such as carbon dioxide (CO2), that increasingly absorb some of the outgoing longwave radiation and trap it in the atmosphere. Energy accumulates in the climate system, and warming occurs. But in a paper out this week in the Proceedings of the National Academy of Sciences, MIT researchers show that this canonical view of global warming is only half the story.
In computer modeling of Earth’s climate under elevating CO2 concentrations, the greenhouse gas effect does indeed lead to global warming. Yet something puzzling happens: While one would expect the longwave radiation that escapes into space to decline with increasing CO2, the amount actually begins to rise. At the same time, the atmosphere absorbs more and more incoming solar radiation; it’s this enhanced shortwave absorption that ultimately sustains global warming.
“The finding was a curiosity, conflicting with the basic understanding of global warming,” says lead author Aaron Donohoe, a former MIT postdoc who is now a research associate at the University of Washington’s Applied Physics Laboratory. “It made us think that there must be something really weird going in the models in the years after CO2 was added. We wanted to resolve the paradox that climate models show warming via enhanced shortwave radiation, not decreased longwave radiation.”
Donohoe, along with MIT postdoc Kyle Armour and others at Washington, spent many a late night throwing out guesses as to why climate models generate this illogical finding before realizing that it makes perfect sense — but for reasons no one had clarified and laid down in the literature.
They found the answer by drawing on both computer simulations and a simple energy-balance model. As longwave radiation gets trapped by CO2, the Earth starts to warm, impacting various parts of the climate system. Sea ice and snow cover melt, turning brilliant white reflectors of sunlight into darker spots. The atmosphere grows moister because warmer air can hold more water vapor, which absorbs more shortwave radiation. Both of these feedbacks lessen the amount of shortwave radiation that bounces back into space, and the planet warms rapidly at the surface.
Meanwhile, like any physical body experiencing warming, Earth sheds longwave radiation more effectively, canceling out the longwave-trapping effects of CO2. However, a darker Earth now absorbs more sunlight, tipping the scales to net warming from shortwave radiation.
“So there are two types of radiation important to climate, and one of them gets affected by CO2, but it’s the other one that’s directly driving global warming — that’s the surprising thing,”
…says Armour, who is a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Out in the real world, aerosols in air pollution act to reflect a lot of sunlight, and so Earth has not experienced as much warming from shortwave solar radiation as it otherwise might have. But the authors calculate that enough warming will have occurred by midcentury to switch the main driver of global warming to increased solar radiation absorption.
The paper is not challenging the physics of climate models; its value lies in helping the community interpret their output. “While this study does not change our understanding of the fundamentals of global warming, it is always useful to have simpler models that help us understand why our more comprehensive climate models sometimes behave in superficially counterintuitive ways,” says Isaac Held, a senior scientist at NOAA’s Geophysical Fluid Dynamics Laboratory who was not involved in this research.
One way the study can be useful is in guiding what researchers look for in satellite observations of Earth’s radiation budget, as they track anthropogenic climate change in the decades to come. “I think the default assumption would be to see the outgoing longwave radiation decrease as greenhouse gases rise, but that’s probably not going to happen,” Donohoe says. “We would actually see the absorption of shortwave radiation increase. Will we actually ever see the longwave trapping effects of CO2 in future observations? I think the answer is probably no.”
The study sorts out another tricky climate-modeling issue — namely, the substantial disagreement between different models in when shortwave radiation takes over the heavy lifting in global warming. The authors demonstrate that the source of the differences lies in the way in which a model represents changes in cloud cover with global warming, another big factor in how well Earth can reflect shortwave solar energy.
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The paper: http://www.pnas.org/content/111/47/16700 (open access)
Shortwave and longwave radiative contributions to global warming under increasing CO2
Significance
The greenhouse effect is well-established. Increased concentrations of greenhouse gases, such as CO2, reduce the amount of outgoing longwave radiation (OLR) to space; thus, energy accumulates in the climate system, and the planet warms. However, climate models forced with CO2 reveal that global energy accumulation is, instead, primarily caused by an increase in absorbed solar radiation (ASR). This study resolves this apparent paradox. The solution is in the climate feedbacks that increase ASR with warming—the moistening of the atmosphere and the reduction of snow and sea ice cover. Observations and model simulations suggest that even though global warming is set into motion by greenhouse gases that reduce OLR, it is ultimately sustained by the climate feedbacks that enhance ASR.
Abstract
In response to increasing concentrations of atmospheric CO2, high-end general circulation models (GCMs) simulate an accumulation of energy at the top of the atmosphere not through a reduction in outgoing longwave radiation (OLR)—as one might expect from greenhouse gas forcing—but through an enhancement of net absorbed solar radiation (ASR). A simple linear radiative feedback framework is used to explain this counterintuitive behavior. It is found that the timescale over which OLR returns to its initial value after a CO2perturbation depends sensitively on the magnitude of shortwave (SW) feedbacks. If SW feedbacks are sufficiently positive, OLR recovers within merely several decades, and any subsequent global energy accumulation is because of enhanced ASR only. In the GCM mean, this OLR recovery timescale is only 20 y because of robust SW water vapor and surface albedo feedbacks. However, a large spread in the net SW feedback across models (because of clouds) produces a range of OLR responses; in those few models with a weak SW feedback, OLR takes centuries to recover, and energy accumulation is dominated by reduced OLR. Observational constraints of radiative feedbacks—from satellite radiation and surface temperature data—suggest an OLR recovery timescale of decades or less, consistent with the majority of GCMs. Altogether, these results suggest that, although greenhouse gas forcing predominantly acts to reduce OLR, the resulting global warming is likely caused by enhanced ASR.
Note: This study was published in November 2014, but was not covered by WUWT then. Thanks to Dennis Wingo for bringing it to our attention.
I cannot say I have read the paper but it seems to me they have discovered something that I and some of us here on wuwt already knew. The climate changes as the sun’s radiation changes over time AND as earth’s inside iron core re-aligns with that of the sun: the magnetic stirrer effect.
FYI, we all know of the following solar cycles (SC’s) :
11(Schwabe) , 22 (Hale), 88 (Gleissberg) , 210 (DeVries), 1000 (Eddy), 2400 (Bray), years, respectively.
{proven data for these cycles exist}
The changes can be seen in my data, for example, you can see the half cycle of the Gleissberg shown in my graph.
GHG’s [also] deflect SW to space,
and what the researchers should do to prove that a GH effect exists is to show us a balance sheet of each GHG as to how much OLR is trapped versus how much SW is back radiated to space, converted to some kind of energy calculation.
My data tell me that there is no man made warming so I would say the net effect of more GHG (CO2 + H2O) is zero or very close to zero and it compares to nothing with the various effects of the SC’s.
“Donohoe, along with MIT postdoc Kyle Armour and others at Washington, spent many a late night throwing out guesses as to why climate models generate this illogical finding before realizing …
THIS IS NOT SCIENCE!
~~~~~~~~~~~
I spend about the same time and my guess is that you and your guesses are wrong, and the climate models are no match for reality.
Still better than Mikey the Mann’s hockeyschtick, that was made up deliberately and conceived with trickery to deceive.
“However, a darker Earth now absorbs more sunlight, tipping the scales to net warming from shortwave radiation.”
*****************
So the entire theory now hangs on a ‘darker earth absorbing more sunlight’? How much by surface area is now ‘darker’ than before and thus has reduced albedo? 2%? 1%? 0.5%? Less? (and over how many months of the year for that matter?) From there how realistic is it that such a tiny % of earths surface – in already cold areas that receive far less incoming solar than hot areas, holds the balance of power on global temperature surface warming? Sounds like yet more propping up of AGW by confected theory.
Clean air acts worked, and resulted in warming. Why can’t we just leave stuff alone?
Patrick MJD November 13, 2017 at 4:33 am
Clean air acts worked.
I think this gets overlooked and if as they say, “aerosols in air pollution act to reflect a lot of sunlight” then we should see warming because of cleaner skies, at least in the ‘developed’ world.
CheshireRed November 13, 2017 at 4:26 am
I think the idea we can measure how things will warm just by measuring albedo is too simplistic. Forests and lakes are darker than deserts / salt lakes, but forests and lakes are cooler than the latter. Of course that will be because of evaporation but either way they will be cooler.
I agree. Albedo is pitched as another instant explanation to this issue and as a positive feedback that drives warming but it’s just too simplistic and as so often, way too convenient to their cause. Anything to keep AGW on life-support, eh?
I suppose it’s easier to attribute ‘blame’ to the life giving photosynthesizing CO2 gas & try limit to industrial development of the 3rd world, that has given us in the 1st/2nd world such a deluxe lifestyle from ‘caveman’ days, but the general public don’t really get blasted with info on other GHGs (except the GreenWash) so found this from this article (found from a few clicks from the above):
https://ecometrica.com/assets/GHGs-CO2-CO2e-and-Carbon-What-Do-These-Mean-v2.1.pdf
All of course ignoring other effects of Sun, Clouds, the uneven distribution of solar radiation on this little planet and of course Milankovic cycles etc in this very brief history of time.
These guys have got it backwards too.
The warming of the late 20th century was caused primarily by reduction in cloud cover.
https://wattsupwiththat.com/2017/04/30/sun-cloud-ocean-update/
Cloud cover decrease was responsible for about 90% of the global warming from 1981 to 2009, increased CO2 was responsible for about 10%. [1981-2009 was the full date range of available cloud data.].
The resulting warmer surface sends more IR radiation out into space, and the extra CO2 intercepts only a part of it. This is the cause behind their observation that “While one would expect the longwave radiation that escapes into space to decline with increasing CO2, the amount actually begins to rise.”
So when they say “At the same time, the atmosphere absorbs more and more incoming solar radiation; it’s this enhanced shortwave absorption that ultimately sustains global warming.”, this is where they have got it backwards: The absorption of more SW is the natural result of a decrease in cloud cover. So it isn’t a reaction to CO2’s warming, it is the warming. “Sea ice and snow cover melt” is trivial compared to cloud cover decrease, because it involves a much smaller area placed where there’s a lot less solar radiation.
NB, it’s the ocean that absorbs the SW, not the land or the atmosphere.
Mike,
You said, “The warming of the late 20th century was caused primarily by reduction in cloud cover.” That has always struck me as a better explanation for the retreat of glaciers than the miniscule, claimed increase in average global surface temperatures, with most of the increase at high latitudes, at night, and in the Winter, where it is already cold enough to freeze.
Indeed. We know that warming began prior to the industrial revolution and we have anecdotal accounts from history as well as scientific proxy data that cold periods were often associated with literal dimming of the sun. Clouds, especially high level clouds nucleated from sulfate aerosols, is the culprit.
“during this year a most dread portent took place. For the sun gave forth its light without brightness… and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear” — Procopius, 6th century
If this paper means anything, then we would have seen the authors and MIT cast aside as climate deniers by now.
More speculation about speculation about speculation…
Something about that word “impacting” bothers me.
Verbing nouns is an American thing.
“The atmosphere grows moister…”
But if one believes NOAA data, it has not but is actually getting drier.
Yes, that is my understanding. Could you link to the data?
I get it from http://www.climate4you.com/ Go to “Climate + Clouds” I am sure you can also get it directly from NOAA.
“The authors demonstrate that the source of the differences lies in the way in which a model represents changes in cloud cover with global warming, another big factor in how well Earth can reflect shortwave solar energy.”
Yes, and cloud cover can be greatly affected by the land over which the air travels and changes in land use can change cloud cover. Have there been any changes in land use in the last 200 years compared to the previous millennia?
The entire ‘scientific’ premise of ‘global warming’ is based on the erroneous concept of ‘greenhouse gases’.
If CO2 in the atmosphere absorbs infrared energy from the sun and heats the atmosphere, what would happen to an atmosphere without CO2? The infrared energy would pass through the atmosphere and strike the surface, where it would be absorbed and converted into heat.
Where would this heat go? It would heat the air that is in contact with the warmed surface.
Either way, the infrared energy ends up heating the atmosphere. The presence or absence of a gas that absorbs infrared energy does not affect the total amount of energy transferred to the atmosphere. The source of all that infrared energy is the sun. The gas may, at best, provide a secondary path for some of the energy to get absorbed by the atmosphere.
Conversely, the emission spectrum of a gas is identical to its absorption spectrum. CO2 radiates infrared radiation (in ALL directions!) as well as it absorbs the same radiation. Whether or not a specific molecule of CO2 absorbs or radiates depends on several factors, but mostly the relative total kinetic energy of the molecular vibrations compared to the average total kinetic energy of the molecular vibrations of it’s molecular neighbors – i.e. the ‘temperature” of the surrounding gas. The presence of more CO2 in the atmosphere increases its ability to radiate energy at those same wavelengths.
The novelty level within this paper seems to be zero.
It has been said for almost 50 years that the direct effects of GHGs are low; approximately 1C increase for each doubling of CO2 as an example.
If AGW is dangerous, it is due to the feedbacks associated with a warming globe.
This paper is just reiterating common knowledge.
“While one would expect the longwave radiation that escapes into space to decline with increasing CO2”
This is a ridiculous statement. Longwave radiation leaving the Earth is solely affected by the Earth’s temperature, otherwise you’d get short-term catastrophic warming. CO2 can only delay individual photons from escaping, not change the net energy balance.
“OLR takes centuries to recover”
Why and based on what knowledge?
“we have the global warming physical process backwards”
Agreed. No need to read your paper then.
Short version: The models are consistent with the pause. Longer term its worse than we thought. Send mony
” I really don’t know clouds at all ” – joni mitchell
there is a new paper out that suggests that the CO2 absorption spectra is already fully (or substantially already fully) saturated, such that CO2 at late 20th century levels does little, if anything at all. See:
Solution of the Greenhouse Effect equations shows no increase in Earth’s surface temperature from increase in carbon dioxide (PDF Download Available).
Available from:
https://www.researchgate.net/publication/319324166_Solution_of_the_Greenhouse_Effect_equations_shows_no_increase_in_Earth's_surface_temperature_from_increase_in_carbon_dioxide [accessed Nov 13 2017].
“If there were no leakage, the upwelling infrared radiation from the Earth’s surface would be equal to the incoming solar radiation absorbed by the atmosphere plus twice the solar radiation absorbed by the surface. ”
Simple, elegant, easy to understand(*). However, you have to consider that convection belongs in the leakage, as a not radiative way for surface to give energy to atmosphere.
Notice that according to the (awful, flat-earth) mainstream Earth energy budget,
A incoming solar radiation absorbed by the atmosphere ~67
B solar radiation absorbed by the surface ~168
A+2B = 403. Note this is maximum, no leakage, input to surface
C convection (part of leakage) ~102
D upwelling infrared radiation from surface: ~350 ( to atmosphere ~310, direct to space — leak– ~40)
C+D= 452 total energy loss by the surface
452 > 403, i.e. surface emits/transfers more than it can possibly recieve even in the no leakage case, so something is wrong in this Earth power budget, massively (in the ~50W/m² magnitude, 10x more than supposed anthropo forcing!).
(*) you are looking at a steady state solution where
A (atm in from sun) +B (surface in from sun) = C (global out to space = atmosphere out because no leakage surface to space and no leakage non radiative atmo to space, also backradiation from atm to surface because as much down as up)
D (surface out radiation = surface in because equilibrium and no convective leakage) = B + C = A+2B.
QED
More specifically, the energy that the dipole molecule absorbs must be EXACTLY the energy needed to bump the molecule into the quantized vibrational state. It will never, under any known physical reality, absorb more or less than the exact energy needed, and once it’s already in the quantized vibrational state, it IS transparent to those wavelengths. If all the OLWIR in those bands is already being absorbed and reemitted, any additional molecules will make little difference. The only additional energy will come from the increased probability that when molecules collide in the atmosphere, one of them will be a CO2 molecule that will lose some vibrational energy to translational kinetic energy on collision, so the additional energy will be fractions of the quantized energy level (very little energy).
“If all the OLWIR in those bands is already being absorbed and reemitted” (condition 1)
Then is it not the case that
“any additional molecules” (of the same kind)
will absorb any additional OLWIR that may arise (such as from an increasing surface temperature?
I’m not saying that the first condition of absorption and re-emittance will (or will not) lead to an increased surface temperature, I’m asking by what logic increased OLWIR, from any cause, would not interact with the additional molecules, adding to the total of condition 1.
I don’t think an increase in surface temperature increases the amount of each individual band of OLWIR, it slightly shifts the overall radiation to higher frequency/energy bands. If you believe the oft cited data, condition 1 was met before the industrial revolution.
@richard Verney
“half” is incorrect.
The molecule acts like a sphere, so 62.5% of radiation going in the direction of the molecule goes back to the direction where the light came from.
You can compare it a bit with putting on your bright lights in misty, moist conditions: the light is returned to you in your face.
{we are talking of light in the wavelength area where the molecule ‘absorbs’}
this reasoning goes for both SW (going back to space) and OLR (going back to earth) where there is absorption.
I was just stating the claim, ie., what proponents of AGW and the radiative GHE claim about the workings of their ‘theory’.
I agree that as a matter of geometry, less than half will find their way back to the surface.
Richard Verney
I think you did not get it.
The figure is 62.5% in the direction where the light came from. Not 50% or less than 50%.
Perhaps try and understand exactly how the GH and the anti GH effect works.
Note that on a cold winters night, when clouds come in, the minimum T in the night increases, as the IR radiation from earth hits on the water / water vapor and returns back to earth?
So, heat OLR is trapped by the clouds [at night]
During the day, clouds and GHG return [some] SW back to space.
Perhaps read this paper and understand exactly what is happening in fig 6 and 7: Follow the SW of the lines of H2O and CO2 that was deflected from earth to the moon and measured back on earth and tell me exactly what you see is happening?
http://astro.berkeley.edu/~kalas/disksite/library/turnbull06a.pdf
Do you see that the CO2 is also cooling the atmosphere?
The wavelength areas of the molecule where absorption takes place, act like a mirror, returning the light, 62.5 % in the direction where it comes from.
Hence, more CO2 is [also] cooling the earth.
henryp November 13, 2017 at 5:52 am
@richard Verney
“half” is incorrect.
The molecule acts like a sphere, so 62.5% of radiation going in the direction of the molecule goes back to the direction where the light came from.
No the atmosphere is so thin that any emitting molecule is very close to the surface (radius ~6500km), the delay time after absorption is so long that the molecule emits randomly wrt the direction the light came from. The angle subtended by the earth at the emitting molecule is very close to 2pi steradians so the proportion of light scattered back to the earth is very close to 0.50. Henry appears to confuse the process with elastic scattering by liquid spheres.
“As longwave radiation gets trapped by CO2, the Earth starts to warm, ”
No it doesnt. CO2 isnt an energy source, hence it can’t heat anything. All CO2 can do is act as a bit of insulation, a poor one at that, hence all CO2 is KEEP the earth a bit warmer, not MAKE the earth warmer.
Exactly correct! A tiny few extra molecules basically replicating what many more water molecules are already doing.
longwave emitting up from the earth as longwave emitting down from co2 – really?
So, where are the computer model results that replicate the historical climate?
If these models were any good, they could replicate the climate from, say, the year 900 up until 1800; a time period before the industrial revolution, thus eliminating the affects of human activity on the climate. Yep, one less variable to mess around with – simplifies things.
The year 900 to 1800 period also includes the Medieval Warm Period and the Little Ice Age. Surely such very pronounced climate periods can easily be modeled by today’s “scientists,”
After all, they claim to have a good understanding of climate science; so good in fact, they are telling us what the climate will be like 100 years into the future
If they can predict the future climate, than surely, replicating the historical climate should be easy.
I find it puzzling that so many are willing to comment on the latest “research” findings of the AGW proponents, yet no body seems to be asking where are the climate “replication” results that can shed light on the validity of the climate models.
Where are they folks ???
Where’s the beef??
“As longwave radiation gets trapped by CO2, the Earth starts to warm, impacting various parts of the climate system. Sea ice and snow cover melt, turning brilliant white reflectors of sunlight into darker spots. The atmosphere grows moister because warmer air can hold more water vapor, which absorbs more shortwave radiation. Both of these feedbacks lessen the amount of shortwave radiation that bounces back into space, and the planet warms rapidly at the surface.
Meanwhile, like any physical body experiencing warming, Earth sheds longwave radiation more effectively, canceling out the longwave-trapping effects of CO2“
Perhaps one of the most painfully stupid explanations I’ve ever read. Any physical body experiencing warming sheds LW radiation more effectively. The same LW radiation that leaves the Earth less effectively, due to the presence of increased CO2. So:
1) There is LESS LW radiation leaving the Earth because of increased CO2.
2) As a consequence, the Earth gets warmer.
3) So there is also MORE LW radiation leaving the Earth because of increased CO2.
Increasing levels of CO2 causes an incredecrease in the amount of LW radiation leaving the Earth. It doesdoesn’t increase the amount of LW radiation leaving the Earth AND it also doesdoesn’t decrease the amount of LW radiation leaving the Earth.
I mean, it ISN’T, and can’t possibly be, observed, that increases in the amount of CO2 cause a decrease in the amount of LW radiation. What IS in fact observed, is the exact opposite. BUT, since we already KNOW that our theory is DEFINITELY CORRECT, then decreases in the amount of LW radiation leaving the Earth, with rising CO2, are a given.
But, of course, it’s also a given that the opposite is true. Increasing CO2 means the amount of LW radiation leaving the Earth increases. Like we said all along.
The incredecrease in LW radiation leaving the Earth is what the GHE is all about.
It’s not a disgrace to science. It’s a gooddisgrace to science. It’s an icredecrease to our knowledge as a species about the world around us. It’s a helphindrance to humanity. We arearen’t obviously stupid.
Oh look! Their already – Goldbergian manmade climate contraption has a couple more climate levers added to all the other knobs and gizmos. Shiny!