Donohoe et al: The missing piece of the climate puzzle

Posted: November 20, 2014 by tallbloke in Analysis, atmosphere, climate, general circulation

This article caught my eye because Isaac Held stuck his oar in. Talkshop readers will have a field day with this I think.

Researchers show that a canonical view of global warming tells only half the story.
Genevieve Wanucha | Program in Atmospheres Oceans and Climate
November 10, 2014

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.

The work was supported by the National Oceanographic and Atmospheric Adminstration, the James S. McDonnell Foundation, and the National Science Foundation.

The paper is here

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Here’s my comment (awaiting moderation at this time)

“While one would expect the longwave radiation that escapes into space to decline with increasing CO2, the amount actually begins to rise.”

Because the error of measurement of TOA energy balance is 5 times larger than the theoretical signal from increased co2, this can’t be determined empirically. As Kevin Trenberth said “Our instrumentation isn’t good enough”.

But if the amount of energy arriving at the TOA from the Sun is constant, and more longwave is leaving for space, then the first law of thermodynamics tells us the Earth is cooling overall. Same energy in – more energy out. This means that rather than accumulating somewhere below surface in the southern ocean, the ‘missing heat’ is now somewhere past Alpha Centauri.

So if the surface (or more correctly the near surface air) is warming, then what is under discussion is the distribution of energy absorption in the vertical profile. The article mentions two places:

“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.”

However, empirical observation tells us global sea ice is at an all time high since the beginning of satellite records, and the last reliable water vapour dataset tells us overall humidity has decreased since 2000, with a small increase near the surface. More absorption of shortwave in the near surface air means less shortwave reaching the actual surface and being absorbed. That may go some way to explaining the increase in sea ice and the cooling (since the mid 1980’s according to the Reynolds dataset) of the higher latitude southern ocean surface.

 

Comments
  1. Alan Poirier says:

    Slowly but surely they are coming around to the simple understanding the GHE is a function of the atmosphere as a whole and not a relatively insignificant molecule as CO2.

  2. oldbrew says:

    Is there an assumption that additional CO2 just gets added to the system rather than taking the place of an equivalent amount of water vapour?

  3. markstoval says:

    “Slowly but surely they are coming around to the simple understanding the GHE is a function of the atmosphere as a whole and not a relatively insignificant molecule as CO2.”

    Perhaps they are and that would be a great thing. But on the other hand, I got banned by Steve Goddard at “Real Science” for saying Dr. Brown of Duke University and Dr. Peter Morcombe (formerly of Duke University) had pointed out that the CO2 molecule in the lower atmosphere was much more apt to “bump” into a nitrogen or oxygen molecule and give up any receive energy long before it could radiate that photon. In other words; convection rules in the lower atmosphere and not “back radiation”. Apparently Goddard is running a campaign to curry favor with the luke-warmers at WUWT.

    I think that the alarmists and the luke-warmers are totally impervious to logic and observation. Perhaps this generation must pass before a new generation takes a look at way the failed predictions were so off the mark. Even then it may not be possible to rid science of this delusion. Look at the fact that so many people still think socialism works when country after country tried it and it failed to deliver. The ultimate test was 90 years of communism in the old USSR and even Russians agree that was a failure.

  4. David Blake says:

    Interesting, and I would say highly important. For those who aren’t as math-challenged as I am the full paper is here:

    Click to access Donohoe_etal_pnas_2014.pdf

  5. Richard111 says:

    A question for any maths buff; how much energy is absorbed from the sun during daylight against the energy emitted during the hours of darkness? Limit this query to CO2 for now. My poor maths make it energy absorbed over the 2.7 AND the 4.3 micron bands over 12 hours of daylight FAR EXCEEDS energy emitted over 13 to 17 micron band during 12 hours of darkness.

  6. Richard111 says:

    I tried to read the paper and gave up when they talked about energy being stored in the atmosphere for decades. Ever spent any time in a desert? Daytime temperatures with the sun overhead can hit 50C yet before dawn of the next day temperature is down to ZERO! This can happen day after day. I simply cannot believe the atmosphere can store energy.

  7. doug Proctor says:

    Change in albedo and change in humidity. Lower albedo could be less clouds or more dirt and water. Regardless not IPCC narrative as increased surface SI is not supposed to be significant.

    Those who propose don’t check? No increase in humidity.

    Albedo change is regional not global here. Warming is therefore polar and redistributed, again not IPCC narrative.

    Never have so many different views been considered part of a consensus.

  8. catweazle666 says:

    The atmosphere grows moister because warmer air can hold more water vapor, which absorbs more shortwave radiation.

    The now widely acknowledged 18 year pause and Solomon et al’s paper showing that stratospheric water vapour declined by ~10% post 2000 would tend to indicate otherwise.

    https://www.sciencemag.org/content/327/5970/1219.abstract

  9. Husq says:

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  10. Will Janoschka says:

    None of your article makes any sense! It is all bullshit claims with no physical evidence whatsoever! Why play with pink effalumps?

  11. Konrad says:

    “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.”

    My response to Donohoe is simply “Stop shovelling it on while we can all still breathe!”

    This is just frantic hand-waving trying to cover up the fact that rising OLR has tracked the early 20th century rise in atmospheric temperatures and the physics defying drivel of the climastrologists is collapsing around their ears.

    ”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.”
    Oh, so everybody knew about the “unicorn to rainbow ratio going negative” thing, but no one had thought to “clarify and lay down in the literature”? Rubbish, this new albedo change excuse is as pathetic as the 55 or more excuses for the 18+ years of no warming. Just where in their frantic blackboard scribbling is an increase in the speed of tropospheric convective circulation (and thereby energy transport from the surface) for increased OLR and increased radiative subsidence? Nowhere, that’s where.

    How do we know the paper is complete dross? Well an examination shows they are using GISSTEP as a metric, That’s strike one. They have tested their crazed albedo excuse using CMIP5 GCMs, which cannot do CFD in the vertical dimension, that’s strike two. The authors claim “the greenhouse effect is well established”, that’s strike three and you’re out.

    Add Donohoe et. al. to the burgeoning shame file…

  12. ntesdorf says:

    Alarmists for CAGW are very slow to take up new ideas apart from recycled CAGW ideas. Observation and data are low on their critical agenda. It may take as long for the Alarmist belief to pass as it took for the Communism Hoax to be undone. The Communist Hoax took 70 or more years and so we should not expect fast results. Even now some people still believe in Communism (Socialism) and just think that it was never given a fair test even after country after country tried it and failed miserably.

  13. Mr Pettersen says:

    I think this is the ultimate proof of co2 not trapping heat. The long wave radiation is not affectet by co2. The fact that shortwave increase can be a result of the suns output and thus have absolutly nothing to to with earths co2 level. Knowing the good corelation between sunspots and temperature this paper actually proves the suns shortwave controls the climate. That the authors of the paper didn’t see this gives an ide of how impeard their wiev on global warming actually are. They absolutly have to connect global temperature to co2……

  14. Mr Pettersen says:

    I forgot to say that the earths albedo is a result of the incomming shortwave so the sun actually controls the whole climate. You need cold before ice will freeze. So its not the albedo changing incomming shortwave absorbsion. They got the cause and effect wrong here. Clearly there are big differences in incoming shortwave so ice will grow for a period and then retract for a period.
    So incomming shortwave is the ultimate king of climate.

  15. Bart says:

    So, in a nutshell, they didn’t understand even their own models. Now, they think they understand their models. As far as the real world goes, they’re still adrift.