Study: Interactions between smoke and clouds have unexpected cooling effect

Atomspheric physicists have found that the way wildfire smoke from Africa interacts with clouds over the Atlantic Ocean results in a net cooling effect, which is contrary to previous understanding and has implications for global climate models.

A view from the window of a P-3 aircraft over the Atlantic Ocean. A layer of smoke is visible over patchy clouds.

CREDIT NASA/Kirk Knobelspiesse

Clouds play a prominent role in moderating Earth’s climate, but their role is still poorly understood. Generally, clouds cool the Earth by reflecting incoming sunlight back out into space. Reducing the clouds’ reflectivity–with a layer of pollution, for example–reduces the cooling effect. However, new research in Proceedings of the National Academy of Sciences by physicists at UMBC and collaborators adds a surprising twist to this model.

Every fall, fires race across central and southern Africa, creating so much smoke that it’s clearly visible from space. Wind sweeps the smoke westward over the Atlantic Ocean, where it rises above the largest semi-permanent gathering of clouds in the world. For years, scientists believed that overall, the smoke diminishes the clouds’ cooling effect by absorbing light that the clouds beneath otherwise would reflect. The new study by Zhang and colleagues doesn’t dispute this effect, but introduces a new mechanism that counteracts it by making the clouds more reflective.

“The purpose of this paper is to look at these competing processes. Which one is more important?” asks Zhang. Using data from a LiDAR system on the International Space Station, recent UMBC research found that the smoke and cloud layers are much closer to each other than previously observed. That means the smoke, which is in the form of tiny particles known as aerosols, can physically interact with the clouds, affecting how they form at the microscopic level. Previous studies usually overlooked these microphysical changes due to aerosols’ interactions with the clouds.

Clouds need “seeds” to grow. A seed can be any tiny particle around which cloud droplets condense. Aerosols are perfect for seeding clouds, and with more seeds, many small cloud droplets replace fewer large droplets, which then collectively reflect more light and increase the cooling effect.

The team found that in smoky conditions, there are almost twice as many “seeds” per cubic centimeter. By running computer simulations under different conditions, they determined that overall, “The seeding effect is winning,” Zhang says. So, contrary to long-held understanding, the overall effect of the hovering smoke on the clouds near Africa appears to be a cooling one.

Zhang is quick to point out that this result is not an argument in favor of fires. “Aerosols are a very local phenomenon, and they are also short-lived,” he says, so their cooling effects are short-lived, too. “The lifetime of carbon dioxide and other greenhouse gases,” which are released in abundance when plant material burns, “is hundreds of years.”

The team’s ultimate goal is to refine global climate models by improving how they account for clouds. Zhang’s other Ph.D. student and another co-author, Zhifeng Yang, has contributed to that effort by analyzing data collected by a satellite that stays put in the sky (rather than orbiting Earth) to get a more accurate sense of how cloud cover changes in daily cycles.

The next step is to evaluate existing climate models against the team’s new finding. “Now that we know there are two competing mechanisms, and the seeding effect is winning, we can see whether climate models consider these processes properly when they predict the weather and climate in this area,” explains Zhang.

A new NASA mission called PACE expected to launch in 2020 will aid their efforts. It will be able to detect polarized light, in addition to everything LiDAR can do. “With the new satellite you can look at things from different perspectives,” says Zhang, and develop three-dimensional models of the interactions between aerosols and clouds. “Hopefully we can look at this phenomenon even better.”

Beyond the upcoming NASA mission, what really excites Zhang and his team is the opportunity to play a role in making sure communities around the world have the best information available as they prepare for the effects of climate change.



58 thoughts on “Study: Interactions between smoke and clouds have unexpected cooling effect

  1. Well I guess the obligatory statement about greenhouse gases must now be in any atmospheric research if the researchers hope to still be funded. Be interesting to know what effects the California periodic wildfires have on cloud formation.

    • “… prepare for the effects of climate change.”

      Wonderful words to put at the end of an article that demonstrates the climate models are all cr4p.

  2. So another computer model to understand clouds. Good news though it’s still all about CO2.(Science settled)

  3. Zhang and his team are excited about the prospect of spreading the Warmist Gospel, propaganda, and disinformation worldwide. I guess it makes them feel important. Or something.

  4. “Zhang is quick to point out that this result is not an argument in favor of fires.” Think about the implied hubris of this statement. The assumption is that whether fires occur or not is something that can be debated and ultimately controlled. The western United States has suffered the consequences of this hubris.

    • Ageed. My first thought, however, is that this is a typical condescending climate expert who thinks that people who are not climate expert superhero planet savers are such lamentable rubes that they have to be explicitly told that no, the deliberate setting of fires will not help save us from certain doom. I’ll assume that my assumption is not warranted.

  5. prepare for the effects of climate change

    The climate has been changing all through my life. Usually preparation involves summer clothes for summer and winter clothes for winter.

    • “The Control of Nature” by John McPhee contains a brilliant, detailed account of the mechanics of Californian wildfires and debris flows.

  6. As an old P-3 pilot, I enjoy seeing pictures of the plane. I recognized the engine exhaust before reading the caption under the picture.


      • >>
        But surely that aircraft is a Lockheed Electra.

        You can tell it’s not an Electra because the wings haven’t fallen off. I would not want to fly an Electra into a hurricane (although I’m not too keen on flying a P-3 into a hurricane either). I have flown a P-3 into thunderstorms and that’s quite a ride–especially at night. Also the caption could be lying when it says it’s a P-3.


  7. “Now that we know there are two competing mechanisms, and the seeding effect is winning, we can see whether climate models consider these processes properly when they predict the weather and climate in this area,” explains Zhang. Unless they rewrite the model’s code it ain’t happening, and models don’t consider anything, the code writers have to code the mimicking of ‘consideration’.

  8. “Every fall, fires race across central and southern Africa” – stated as a fact with no explanation. What causes these annual fires? That would be something to talk about instead of the usual “there’s more junk science to do so we need to keep our funding going” statement:
    “The next step is to evaluate existing climate models against the team’s new finding. “Now that we know there are two competing mechanisms, and the seeding effect is winning, we can see whether climate models consider these processes properly when they predict the weather and climate in this area”
    We know climate models can’t predict anything other than the impossible so the answer is obviously no.

    • I wasn’t aware that there even was such a thing as “fall” in central Africa. Without a link to the paper and what the authors actually said it is difficult to assess the claims, beyond it being from the same people who brought us the perennially-failing climate models which fail in every season.

    • Dinsdale,
      I have spent many years in Central Africa and I can tell you that most of these fires are started by peasant tribespeople and a few through natural causes (lightning and hotspots caused by discarded glass bottles).
      As to why they light the fires?, it seems to be an ingrained culture thing. One reason is to remove the tough savanna grass and expose the new green grass shoots for their cattle. Another reason is to herd the wild animals into killing zones (although, from what I observed, the large animals are all gone and their kill nets seem to be filled with rodents, rabbits and the like).
      Whatever the reason, the fires are pervasive and widespread, year after year, as the article states.

  9. Blast from the past — I recognized the engine nacelle of a P3 even before I saw the caption. NOAA flies one or two of these as hurricane chasers (Lockheed Orion).

  10. For years, scientists believed that overall, the smoke diminishes the clouds’ cooling effect by absorbing light that the clouds beneath otherwise would reflect.>

    Seems to be a “straw man” sort of thing. [straw person?]
    I would rather ‘believe’ the darker particles intercept the SW radiation and send 50%, or more, of that energy back out to space. The “clouds beneath” would reflect much of the remaining SW and add to the interactions that direct energy back to space.
    Scientists don’t just “believe” — they test. Get rid of the straw.

  11. The debate over atmospheric aerosols continues, with the data trending towards net cooling effects.
    The climate models need revision….. Very interesting!

  12. CMIP5 models don’t model clouds directly, period. Clouds are parameterized. And when the results are compared to observations, parameterized poorly. Many examples in essay Cloudy Clouds.

  13. Unexpected? This particulate theory was what drove the coming ice age back in the 70s. Did they forget? Pollution actually helps cool the atmosphere. Also, hat something to do with SOx aerosols

  14. ” still poorly understood”…..all of it is poorly understood

    “The lifetime of carbon dioxide and other greenhouse gases,” ,,,,,,,,,, “is hundreds of years.”….so there’s not one thing we can do about it

    • “still poorly understood” … and this new finding is: “contrary to previous understanding”

      Not only are they hiding behind ‘poorly understood’, they had a 50-50 shot at getting it right and chose the contrary option.

  15. Dark contrast to AGW,

    “Turn the coal fired furnace to high in order to Save the world” is all that one can glean from it.

  16. “ Clouds take a prominate role in moderating the climate; but their role is still poorly understood.”

    What an admission!; for a great deal is understood where water is concerned and that is what clouds are all about. Most of this is being ignored as current science is obsessed with radiation and oblivious to the actual energy transfers taking place, particularly during the phase changes involved and the physical movements involved.
    The Steam Tables provide a great deal of information; but I suspect these have been relegated to “Old Hat”only relevant to to trains and such like, forgetting that it still provides the base load of our electrical power.

    Albedo and GHE indeed do have their influences; but the condensation and evaporation processes coupled with the rising movement of humid air have a huge influence albeit complex. No one appears to be looking at these aspects.

    This paper indicates some of the complications which together with the effect of cosmic radiation, has effect on cloud behaviour which basically behaves in accordance with the Rankine Cycle with very large energies being transmitted upwards with a proportion being dissipated into space.
    Fortunately gravity ensures that all this water returns to earth to respeat the cycle and provide the basic thermostat. God bless gravity!!! Otherwise we would be like Venus.

    John T Houghton raised this issue in his “The Physics of Atmospheres” 1091*

    ; but I suspect he is now suffering from cognitive dissonance; for he was one of the originators of the IPCC hypothesis!!, C’est la Vie!

    * Ref: Page 16 .

  17. So air pollution (some of it) has a net cooling effect, and the U.S. made major strides in cleaning up air pollution in the 1970’s onward, then one would predict a slight warming signature in the land temperature record… And this would, naturally, have to be subtracted out to see any effects of increases in CO2 on temperatures.

    Oh wait, I forget they already settled all of this! The doubling of CO2 has a simple linear effect on temperatures. /sarc

  18. Professor Henrik Svensmark and his team and research have concluded that increased cosmic radiation increases the formation of clouds, thereby dampening global temperatures. Weakened solar activity is taking place these days and cosmic radiation increases. The climate models of the IPCC still have a long way to go obviously …

  19. In the week after 9/11 there were no commercial flights over USA. Without con trails in the sky the temp went up. Not down.
    Smoke, smog, clouds all cool.
    Unhindered the Sun’s rays come through the atmosphere and make for a warmer planet.
    No exactly rocket science!

    • I noticed a correlation between major storms on the west coast of the US, and higher global temps approximately 12 to 20 months afterwards. Those major storms generally mean heavy rains at locations across the US as the storm systems move east. It looks to be similar to what occurs several years after a volcano, once the skies clear.

  20. “their role is still poorly understood” .. So let me improve that understanding. Clouds are heating Earth, not cooling it!!! The data clearly show that temperatures are the higher, the more clouds there are. This is a global phenomenon, but even works where it is most unlikely .. in the tropics with low clouds.

    And even then, overcast skies are substantially colder due to rain and thunderstorms, which somewhat masks the radial heating effect of clouds..

    To anyone who can not believe reality .. I have no problem sharing the raw data and the analyzing program hereto.

    • Leitwolf, my data shows that taking aspirin causes headaches. This as a result of hundreds of blood tests on people complaining of headaches. My boss said I had the causation backwards. I’m still in shock that he would deny such a high R^2 correlation.

    • “Joe Bastardi was forecasting this Artic blast hitting western Europe a month ago”
      Not where I like Leitwolf.

    • Your answer and graph are meaningless, clouds have both warming and cooling parts and they vary widely.
      Without providing background to your graph it’s like most data that seems to kick around in climate science a wild guess.

  21. Science is never settled where computer modeling is concerned. Computers are a great tool for spotting patterns in an individual data set of known values. But they should never be used as a crystal ball to predict future events. Between the decrease in solar output, the compression of the earth ‘s magnetic field and an increase in cosmic radiation, all of which have been shown to increase cloud cover and density, would this not lead to global cooling? Adding partials of any kind, including aerosols from volcanic eruptions or fires, only add to the cooling effect, as is born out by the ice core records. A true scientists questions everything and doesn’t come to a consensus with others. They allow the facts to speak for themselves.

  22. Previous studies, particularly one of the largest ever conducted tracking smoke, show that Southern winter grass fire smoke travels from Botswana and South Africa to Australia.

    The reason is the prevailing wind is from the NW and continues off the coast before heating East.

    I admit to being surprised to hear it heads West to the Atlantic. That would be in summer when major fires are rare to few.

  23. [blockquote] …collected by a satellite that stays put in the sky (rather than orbiting Earth)…[/blockquote]

    NO, just NO.

    The satellite is still orbiting the Earth, it is just a geostationary orbit so it stays over the same spot. But it most certainly IS in orbit.

  24. Ah so, agw is real n its fires that hide the warming, ok got it. My dog also ate my project documents the night before deadline day

  25. “…as they prepare for the effects of climate change”. I’m happy Zhang is excited by that. Perhaps he or somebody else (Nick Stokes?) could tell everyone what those effects have been?

    A warming planet hasn’t made water less scarce. Quite the opposite. Tropical, sub-tropical and temperate storms are no more frequent, in fact they are less frequent. The children still know what snow is and many are learning to skate for the first time… Winters can still be very cold in many temperate areas even in a mildly warming world. Antarctica expanded it seems during the recent warming….not what the models predicted. In fact, all the main predictions of the climate alarmist cult have been falsified. The gcms are all way off (the rate of T change is significantly lower than the alarmists predicted at this point and absolutely nothing to be alarmed about. In fact, policy should be directed at trying to stop the planet get into a steep cooling phase (perhaps through encouraging fossil fuel energy consumption).

    So what exactly are the effects of climate change?

    They all seem to be positive. In fact, since man made CO2 emissions have gone from 300 to 400ppm (thereabouts) the planet as greened by around 10%. ALl that ecological productivity and very little climate downside!! What exactly is the problem with a warming planet that is clearly largely temperature insensitive to the plant food CO2? In a more benign climate of a mildly warming world?

    The climate change cult is one gigantic economic and political scam. Designed to redistribute wealth from the majority to the few, to reinforce the poverty cycle everywhere, and to use as a distraction to constant war mongering to disrupt regions to cause mass migration into the West. Through such means, the CO2 (energy) scam pursued by the international socialist ideologues (the so-called ‘globalists) aims to impoverish and enslave the majority of humanity.

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