Study reveals how particles that seed clouds in the Amazon are produced

GOAmazon researchers describe in Nature the role of clouds as transporters of particles between the ground and the upper atmosphere. New knowledge will enhance climate models

A study published in the journal Naturesolves a mystery that has puzzled scientists for over a decade: the origin of the atmospheric aerosols that contribute to cloud formation above the Amazon rainforest in the absence of local sources of pollution.

Research shows the role amazon's clouds as transporters of particles between the ground and the upper atmosphere. CREDIT Eduardo Cesar

Research shows the role amazon’s clouds as transporters of particles between the ground and the upper atmosphere. CREDIT Eduardo Cesar

Aerosols are microscopic particles suspended in the atmosphere. They play several essential roles in the climate system. For example, most clouds owe their existence to aerosols, because the water vapor in the atmosphere condenses on them to form cloud droplets that eventually precipitate as rain. These seed-like aerosol particles are called cloud condensation nuclei, the authors explain.

According to the latest findings of the research project, conducted with FAPESP’s support as part of the Green Ocean Amazon Experiment (GOAmazon), particles that serve as precursors of cloud condensation nuclei form in the upper atmosphere and are carried down toward the ground by clouds and rain.

“We tried for at least 15 years to measure the formation of new aerosol particles in the Amazon at ground level and the result was always zero. The new nanometric particles simply didn’t turn up there. Measurements were made on the surface or in aircraft flying no higher than 3,000 m. We only found the answer when we looked much higher up,” said Paulo Artaxo, a professor at the University of São Paulo’s Physics Institute (IF-USP) and a co-author of the article.

According to Artaxo, the Amazon rainforest naturally emits gases known as volatile organic compounds (VOCs), including terpene and isoprene. They are swept into the upper atmosphere by cloud convection and can soar as high as 15,000 m, where the temperature is about minus 55 degrees Celsius.

“At these very low temperatures, the VOCs condense and form tiny particles measuring 1-5 nm,” Artaxo explained. “These nanoparticles absorb gases and collide with each other, rapidly agglomerating and growing to a size large enough to make them cloud condensation nuclei, typically more than 50-70 nm.”

At high altitudes, he added, particle agglomeration is facilitated by low atmospheric pressure, low temperature, and the vast numbers of particles in circulation there.

“Eventually one of these giant convective clouds generates a strong downdraft of air and precipitates as rain, so that the particles plunge down toward the ground,” Artaxo said.

Surprising discovery

Some of the measurements presented in the article were made in March 2014 during the Amazon’s rainy season by a Grumman Gulfstream-1, a research aircraft capable of flying at 6,000 m, or nearly 20,000 ft, and owned by Pacific Northwest National Laboratory (PNNL) in the US.

Another dataset was obtained between March and May 2014 at the Amazon Tall Tower Observatory (ATTO), which is operated by Brazil’s National Institute of Amazon Research (INPA). The ATTO is 320 m high and located in the heart of the rainforest on the Uatumã Biological Reserve, some 160 km northeast of Manaus – beyond the reach of urban pollution.

Supplementary measurements of aerosols were made at the ZF2 towers around 55 km north of Manaus, and in Manacapuru some 100km west of Manaus at the Atmospheric Radiation Measurement (ARM) mobile facility comprising a number of ground-based and airborne devices developed for climate studies and owned by the US Department of Energy.

“Much to our surprise, we found that the amount of particulate matter in the atmosphere increased with altitude. We would have expected higher concentrations nearer to the ground. We found very large amounts of aerosols at around 6,000 m, the highest the Gulfstream-1 can fly,” said Luiz Augusto Toledo Machado, a researcher at the National Space Research Institute (INPE) and also a co-author of the article.

The initial observation was confirmed by new measurements captured by the German High Altitude & Long Range Research Aircraft (HALO), which can fly at 16,000 m and is operated by a research consortium that includes the German Aerospace Center (DLR), Max Planck Institute (MPI) and German Research Foundation (DFG).

“We found that in polluted areas there was an extremely high concentration of particulate matter near ground level, which wasn’t the case in pollution-free areas. At high altitudes, however, we found large amounts of particles even in the absence of local pollution sources,” Machado said. “This latest study shows how these nanoparticles are swept down toward the ground by rain to form new populations of particulate matter that act as cloud condensation nuclei at low altitudes.”

According to Artaxo, the observation was surprising because above the planetary boundary layer at 2,500 m there is a temperature inversion that usually inhibits the vertical movement of particules. “But we hadn’t taken into account the role of convective clouds as transporters of the gases emitted by the forest,” he said.

The studies performed under the aegis of GOAmazon are proving that VOCs from plants are part of a fundamental mechanism for the production of aerosols in continental areas, he went on.

“The combination of forest-emitted VOCs and clouds makes a very specific dynamic that produces huge amounts of particles at high altitudes, where there weren’t thought to be any. It’s the biology of the forest interacting with clouds to keep the Amazon’s ecosystem functioning,” Artaxo said.

The VOCs soar into the upper atmosphere where wind speeds are very high, and are redistributed around the planet very efficiently. In the Amazon’s case, part goes to the Andes and part to southern Brazil, while some remains in the tropical forest region itself. “At the moment we’re modeling all our data to work out more precisely which regions are affected by VOCs from the Amazon that are transported by atmospheric circulation,” Artaxo said.

Because it was unknown until now, this aerosol production mechanism is not considered by any of the climate models currently in use. “The knowledge will have to be included,” Machado said. “It will help make rainfall simulations more precise.”


80 thoughts on “Study reveals how particles that seed clouds in the Amazon are produced

  1. Well that’s obviously not a Settled Science. They need some skilful modellers to make their results easier to produce,

    • Trees make aerosols. Climate models don’t need enhancing. What they need is to be models of a real planet; not a flat earth stationary one like Kevin Trenberth believes in.

      • Exactly, G. It is complete nonsense for them to say “New knowledge will enhance climate models“, because the models trying to use this new knowledge will be ridiculously inaccurate after just a few iterations. One iteration is typically of the order of 20 minutes.

  2. Gosh. They never realized that convection mattered much or could make air currents and clouds reach to high altitudes above the “boundary layer”.
    And they call themselves “climate scientists”?

    • ….and with this discovery they may also realize, as Willis and a few others have, that these same clouds and currents are excellent at cooling the earth. They can even carry vast amounts of heat higher than almost all of the pesky CO2 molecules up there.

      • And of course when you clear-cut the forests that create such particles…… I have to wonder if cutting down large portions of the Amazon hasn’t played a role in ‘man-made’ climate change- by CAUSING the warming trend!
        Mind you, I am probably wrong. But it seems like it could be a factor.

      • Despite the propaganda you are always hearing, not that much of the Amazon has been cut down.
        Yes a lot is cut down each year, but it grows back.

      • @ClimateOtter I’d be more interested in calculating how much new roads and buildings have contributed to the warming trend…
        Let me correct myself: I’m sure the data is out there, but I need the lack of laziness to find it 🙂

    • I’m very curious about the “boundary layer” myself since 2,500m isn’t very high. When I was a glider pilot we very regularly encountered lift that penetrated that altitude by as much as 35,000′. I can’t imagine why the would consider 2,500m a “boundary”?

      • I too am perplexed by some of the comments, specifically that a Gulfstream-1 has service ceiling of 6000 m. A simple Google check will show that the service ceiling is almost twice that. Any pilot can also relate that circulation and turbulence regularly occur at these altitudes and above.

      • I thought the same thing, initially. But the statement “a Grumman Gulfstream-1, a research aircraft capable of flying at 6,000 m, or nearly 20,000 ft,” doesn’t actually say that that is it’s service ceiling. Just that it can fly at 6,000 m. The “nearly” is just to tell you that 6,000 m is somewhat less than 20,000 ft. All the Gulfstreams are great aircraft, and if you modified the G-1 such that it’s service ceiling was only 20K, it probably wouldn’t be able to take off.
        Retired Aerospace Engineer Jim

      • So what is a gulf stream doing with climate scientists riding around in it. Does it belong to that fake Howard Hughes Lenny fellow that gets terrified in aeroplanes. ??

  3. ““But we hadn’t taken into account the role of convective clouds as transporters of the gases emitted by the forest,” he said.”

    Indeed, convection is the poorly modeled transport mechanism of heat as well. Heat goes up, VOCs (with cooler air) go down, and none of it is modeled properly in the GCMs as these are complex feedbacks that cool the lower troposphere. Vertical mass balance of course is maintained in the airmass. But then there is the modeled, but missing tropical tropospheric hot spot as well for the Church fof CAGW priests to handwave away as well.

    • The GCM’s would handle this parameterized from other models and observations. And it’s evident they will need more observations (including measurements over Congo, Myanmar, New Guinea and similar areas with jungle terrain).
      Eventually we may find out that global warming is partially modulated by plants. And this may require we stop cutting trees and instead work hard to reforest what we cut down.

  4. Wow, there are no cloud nuclei at low levels until heavy rainfall from huge thunderstorms carry them down from the upper atmosphere – resulting in clouds forming at low levels. Sounds to me like a very speculative & poorly thought-out hypothesis. Can’t they just accept that the clouds form because warm & very moist air rises until the vapour cools & condenses?

    • Clouds form when there is warm humid air being cooled and there are particles for the water vapor to condense on. These can be dust, clumps of VOC chemicals encouraged to form by sunlight, blown in from someplace else, other ‘stuff’, or even water. Water behaves like almost no other substance. Water vapor molecules can stick together from surface tension(hydrogen bonding) forces up to multiple nanometers forming condensation nuclei all by themselves.

      • Every substance behaves like no other substance, that’s why they are different.
        But water is certainly weird.
        Who would believe that life itself depends on that 104 degree angle which the H2O molecule strangely assumes.

    • It’s always been known that the presence of particles helps to speed the formation of water droplets.

  5. Not really “new” information: terpenes and isoprene are at the base of the haze of the “blue” mountains in many parts of the world and are the main “pollutant” above the inversion layer, the free troposphere, many times more abundant than e.g. human SOx. While in first instance water repellent, these slowly oxidize in the atmosphere and change into water attractors… That questions the role of human emissions of SOx causing aerosols in the offset of the effect of CO2 in the cooling period 1945-1975 and the current “pause”…
    Again, back to the draft board for the models…
    Here a few links:
    About the isoprene emitted by algal blooms and its effect on clouds.
    About the terpenes load above boreal forests, the SI is free to download.

      • At the time, “intelligent” people laughed at Reagan when he stated that trees are a source of pollution.

      • label the trees:
        Trees are known to the State of California to cause Cancer
        like every thing else – including the box of 7d galvanized nails has the labels

        • There was an allegation that the VOC levels CARB set for the Los Angeles basin were below the production rate by foliage, thus allowing a negatve release level by the industry I was involved in.

    • +1
      I guess if a poor man had designed forest he would have been wrecked as a terrible polluter and the thing forbidden by each and every green bureaucracies GO and NGO.

      • California is purely out of control on this subject, as Tom illustrates. I honestly don’t understand the cause of it but I suspect it has to do with very poor education. The people setting standards and making regulations at the CARB don’t seem connected with reality in any way, so they end up doing more harm than good. There doesn’t appear to be any way to stop it either since, like the EPA, they’re not elected and don’t seem to be under the control of elected reps.
        Say you’re a state legislator that owned a successful retail hardware chain in central California. Some PhD from the CARB tells you they want regulations on VOCs, then presents the proposal. What do you say? You’re a hardware store expert and you don’t know anything about VOCs, the lady has a PhD, you don’t. You end up doing what she tells you to do.
        I don’t see a way around it myself. It’s a cult of “science”. The onus is on the supposedly “educated” to act responsibly and intelligently, but they don’t and we end up with the situation Tom describes; they set VOC standards below the natural emissions of local flora.
        It’s not really “out of control” because it’s never been in control.

      • Oh, another great example of this nonsense is the recent bill in CA, signed and sealed by Governor Moonbeam, to limit CH4 emissions by cattle. Yep, Moonbeam wants to regulate California cow farts.
        These people are true loons.

  6. Australia uses a simular man made process to increase rainfall, it’s called ATLANT.
    Energy is transferred between ground and atmosphere all the time , here’s a video showing the process we see as lightning.
    Not all energy transfer has to be that extreme , trees act like a antenna and transfer energy between ground and atmosphere in both directions , up and down .

  7. Condensation nuclei — oceans are the major source that “nuclei are largely particles of sea salt as the earth is mostly ocean covered, estimated that the bursting of minute bubbles from the sea surface might well produce 1000 nuclei per sq. cm per sec. Amazon is closer to ocean.
    It is also a fact that rainfall is higher at forest zones all over the globe. This is happening basically because forests help condensation nuclei entering the atmosphere. Here topography also plays vital role like in the case of Western Ghats and Himalayan Mountains in Indian Monsoon.
    Dr. S. Jeevananda Reddy

    • Dr . S To desalinate water you boil it (evaporate) don’t you ? It would take a lot of energy to raise salt high enough to become a nuclei for rain. Something like this could be used .
      ” Professional and amateur meteorologists have noted unusual weather patterns several days after each test. Most suspect these irregularities may have been caused by evaporation of surrounding sea water during the tests. Irregularities have been seen and endured across the Pacific, particularly in New Zealand, eastern Australia, and other island groups in the south-west pacific. The disturbances are not consistent with any pre-existing weather patterns.”

      • Sorry, Jmorpuss — nuclei of salt enters the atmosphere through several actions that took place in ocean waters. Temperature is one. spray — waves, cyclonic activity, etc.
        Dr. S. Jeevananda Reddy

      • Dr.S. Isn’t the salt Dissociated as a positive and negative ion (aerosol) which is lofted high enough to help form clouds.
        The salt crystal is a product of evaporation. Sea spray gets blown onto land and the H2O evaporates to leave behind the Na + and the Cl 2 – to form salt crystals.

  8. About time.
    So I’d like to know what role NASA GISS had in this research? It sounds like a DOE/Plank/INPE project from the article. Must look into this further, I know GISS does this work too, at the cost of our crewed spaceflight budget.

  9. Aerosols from pollution is reduced thanks to Clean air act. So we have less clouds now-days, and more heat. Solar brightening!

    • There were some studies done that concluded just that: The LA basin was experiencing less cloud cover and hence less precipitation due to the reduction in particulate matter promoted by the clean air policies imposed.
      So we cleared up the smog only to reintroduce the clean arid skies. We breath much easier, but need to use more chap stick.

  10. Planktons invented cloud generating mechanism billion or two of years even before Amazon and its forests existed.
    NASA-funded research confirms an old theory that plankton can indirectly create clouds that block some of the Sun’s harmful rays.
    The plankton try to protect themselves by producing a chemical compound called DMSP, which some scientists believe helps strengthen the plankton’s cell walls. This chemical gets broken down in the water by bacteria, and changes into another substance called DMS.
    DMS then filters from the ocean into the air, where it breaks down again to form tiny dust-like particles. These tiny particles are just the right size for water to condense on, which is the beginning of how clouds are formed. So, indirectly, plankton help create more clouds, and more clouds mean that less direct light reaches the ocean surface. This relieves the stress put on plankton by the Sun’s harmful UV rays.

    • These tiny [dust-like] particles are just the right size for water to condense on, which is the beginning of how clouds are formed.


      Now, now, now boys n’ girls, after 70 years of being a student of the “natural world” are ya’ll trying to get my learned science all bumbfuzzled and confused, or what?
      First of all. IMLO, there is no such thing as ….. “just the right size particle for water to condense on”, ……. simply because “size” has nothing whatsoever to do with the physical property of a H2O molecule that is defined as “adhesion” that results in “condensation” ……. wherein the “temperature” was/is the primary determining factor.
      Now, as far as the claim that ……. “dust-particulate nuclei being a mandatory requirement for the formation of H2O droplets [aka: clouds, fogs, mists] in the atmosphere” ……. me thinks that it a “chicken n‘ egg solution” to a non-problem,
      And what I mean by a “chicken n‘ egg solution” is, …….. a per se “which came first”, ….. the H2O molecule attracting “dust-particulate nuclei” …… or the “dust-particulate nuclei” attracting atmospheric water (H2O) droplets [aka: humidity, clouds, fogs & mists]?
      Likewise, does the atmospheric water droplets attract the atmospheric CO2 molecules ……. or do atmospheric CO2 molecules attract the atmospheric H2O molecules to form the atmospheric water droplets? Iffen ya all “don’t-get-my-drift” with that question then I will offer a better explanation.
      Ya gotta remember, every raindrop that falls to earth contains carbonic acid (CO2).
      Anyway, I suggest you refresh your “learning” by reading the following, to wit:

      Cohesion: Water is attracted to water
      Cohesion makes a water drop a drop. In a water molecule, the two hydrogen atoms align themselves along one side of the oxygen atom, with the result being that the oxygen side has a slight negative charge and the side with the hydrogen atoms has a slight positive charge. Thus when the positive side on one water molecule comes near the negative side of another water molecule, they attract each other and form a bond. This “bipolar” nature of water molecules gives water its cohesive nature, and thus, its stickiness and clumpability (maybe “dropability” is a better term?).
      Read more @

      And, “sorry bout that” iffen I hurt your pride or feeling with my brash commentary, …… but we are talking science and there is no place in science for one’s emotional thoughts or beliefs.

      • Mr Cogar
        My personal view is contained in the first sentence only, the rest is quote from the NASA’s article. I have no horse in that race, and not bothered either way who is right or wrong: NASA or USGS.
        NASA at least landed man on the moon, while USGS can’t predict an earthquake even a day ahead.
        Take it up with NASA, or even better apply for a USGS grant to prove NASA wrong.
        Good luck

      • Vuc,
        Photosynthetic organisms compete with each other, and are therefore most unlikely to waste resources on cloud producing particles for the sake of the common good. Why then do plants expend resources on production volatile organics?
        * * * * *
        “Plants do not only accumulate terpenes for herbivore defense, but also emit volatile blends in response to herbivory and many other biotic and abiotic stresses. These terpene-containing volatiles attract natural enemies of the attacking herbivores but due to the complexity of these volatile blends, it is difficult to attribute a specific function to a particular terpene.”
        * * * * *
        Although the idea is popular, plants surely didn’t evolve mechanisms for cloud production: that’s just a side effect.

      • Landing a man on the moon was a much easier problem. We knew how to do it, just needed to build the tools.

      • Hi Mark
        Once I drove from SF to LA, took minor roads, took about 4 days days, great country. The USGA beside having seismographs and laser beam sensors along SA fault should install ground electric current, potential and electrostatic, geomagnetic, tidal forces, CO2, sulphur gasses sensors or whatever else .
        Initiate on regular bases small underground explosions along the fault, monitor ‘radar type’ reflected signal captured by all of the sensors. Build up an algorithm then ‘train it’ for predicting location and intensity of more frequent smaller quakes. Within two-three years they might have better idea if not a day but at least few hours ahead of something going off.
        Sticking to the mantra ‘earthquakes are entirely random and unpredictable’ leads nowhere. I doubt that huge forces released during quakes can occur without a precursor of one kind or another.

      • Mr Cogar
        My personal view is contained in the first sentence only, the rest is quote from the NASA’s article.

        Mr, Mrs, Ms, Miss vukcevic,
        Now is a fine time to be informing me and others ….. that only the 1st sentence in your posting in/of “November 3, 2016 at 1:47 am” can be credited to your authorship ….. while the remaining portion of your posting was plagiarized “word-for-word” via the cited NASA article.
        Whenever commentary is plagiarized, either partial or “word-for-word”, ….. then anyone hearing or reading said commentary, and not previously knowledgeable of said, pretty much has to assume that the context/content of said commentary is in fact, …. “original thought”, …… aka: the personal view and/or belief of the author.

      • Hi again Mark
        Each hurricane is a unique event too. In my view hurricanes as constantly moving fast evolving and volatile atmospheric events are far more complex than ‘nearly static’ events in the relatively solid crust and yet hurricane science does pretty good job.
        For the earthquakes first thing required is to identify possible precursors, my friend who is an expert on the stresses in solid structures is certain that they must be there. I experienced two strong earthquakes in my old country, I could hear and sense start of a rumble (type a large heavy vehicle would make), increasing rapidly over period of few seconds before actually things start shaking about.

    • Mr. Cogar
      It is Mr. Vukcevic
      It is a direct quote from the NASA’s article, I provided link, it is your choice whether to read, what to think, and finally what to write.
      I (as probably most of other readers) appreciate only points of science made, valid or not, the rest is not of any concern whatsoever to me.

      • According to Bela Gipp[21] academic plagiarism encompasses:
        “The use of ideas, concepts, words, or structures without appropriately acknowledging the source to benefit in a setting where originality is expected.”

      • Mr. Cogar
        In case you missed it, there is a link immediately following the quote from the NASA’s article. It is there to direct any reader interested to the source of the quote.
        It is not my intention to carry on with this ridiculous exchange, now I’ll wish all the best to you and good bye, sir.

  11. Probably a simplification.
    I spent many years flying the thermals on the eastern slope of the Sierra Nevada, convection pulls warm (somewhat damp) air off the heated surface as “thermals” in clear skies. The thermals hit a thermocline and condense, forming “flat bottom” clouds. We look for these and ride the source to that boundary. Strong thermals will punch right through that thermocline and rise all the way to the tropopause (~42,000′) and even higher, with rare sightings above 70,000′. Downdrafts are created around these strong thermals carrying cold air from the high troposphere (-70F and colder) to the surface. It’s a positive feedback that’s very strong.
    Pilots in unpressurized aircraft or without onboard positive pressure oxygen have frozen to death and died in situations like that an several occasions; the updraft is so strong it exceeds the maximum decent rate of the gliders. Look into hang gliding deaths in the Owens Valley for details.

    • I should have written it’s a negative feedback I suppose. Descending cold air around the thermal eventually cools the surface and the thermal shuts down. It’s like “closing out” in the sense surfers use.

    • Yes, I think that’s correct. It’s sort of a chicken and egg problem I suppose. Once the thermal forms a cloud I guess they could call it “cloud convection” since the cloud marks the convection, but it’s really just convection, as you say.

    • Traffic controllers, like pilots are trained to remain unemotional. It’s quite likely that they were already preparing to guide other planes around you if necessary. The call to you was just a gentle reminder to get your a$$ back down where it was supposed to be.

    • ‘convection pulls warm (somewhat damp) air off the heated surface as “thermals” in clear skies’
      Meteorological question: as moist air is less dense than dry air, do you need damp air to be “warm” for convection to occur?

    • ” moist air is less dense than dry air, do you need damp air to be “warm” for convection to occur?”
      the least dense gas in our atmosphere (not counting the trace gas H or He, is H2O
      it rises by density alone
      when a cubic meter of it condenses to a teaspoonful, then it creates
      a relative vacuum that helps lift more.

    • ” It’s quite likely that they were already preparing to guide other planes around you if necessary. ”
      I was in a small aircraft once when a similar call went out on the radio and the pilot explained that the air traffic controllers didn’t really expect a response. Rather, it was a gentle warning to the other aircraft in the sky that there was a pilot doing the wrong thing.

    • Gnome, Hive: The point is a strong thermal can completely overwhelm a small aircraft, the pilots of which have no overt reason to seek death by freezing or asphyxiation. They didn’t do it intentionally. When it happens to you, it’s truly terrifying.

    • Gamecock asks: “Meteorological question: as moist air is less dense than dry air, do you need damp air to be “warm” for convection to occur?”
      Not simple convection, no. Convection strong enough to overwhelm an aircraft with operating control surfaces? Yes. Absolutely.

  12. At these very low temperatures, the VOCs condense and form tiny particles measuring 1-5 nm,” Artaxo explained. “These nanoparticles absorb gases and collide with each other, rapidly agglomerating and growing to a size large enough to make them cloud condensation nuclei, typically more than 50-70 nm.”
    I am confused. Why don’t the same conditions cause the water vapour to do exactly the same?

    • same as supercooling i guess. creating a liquid-air interface require more energy than released by condensation, and the ratio is higher the smaller the drop.
      that’s where nuclei play their part

    • Erm, so 50 to 70 nm is “just the right size,” as above? Yes, it’s confoozing. And we haven’t even explored the possibility that mutations caused by global warming and ocean acidification could result in man-eating plankton.

    • @Leo Smith
      Water vapor is particularly prone to supercooling. At temperatures above about -55F condensation is mostly heterogenous.
      The shape of isolated water molecules in the solid phase is different from the shape in the gas phase. Growth from individual H2O molecules to dimers, trimers, and so on must be assisted by interactions with some other molecules. You know something is up since ice floats on water.
      Since H2O vapor has a large dipole it interacts readily with charged surfaces of most any composition.

  13. No mention of the millions of tonnes of Saharan dust blown over the S Atlantic that also act as nucleation centers.

  14. My thinking is probably wrong but, if you cut down forests (say, the Amazon) which produce such aerosols, thereby reducing cloud formation, would that not contribute to warming?

    • Yes, but not just from VOC’s. Fresh clear cuts dry out quickly reducing the moisture in the air. Grasses hold onto their moisture better than trees. Grass covered plains and forests tend to compete with trees spreading out into the grass and grass keeping tree seedlings small enough to get grazed out by herbivores. The result depends on the climate. The US used to be largely covered with forest right out into the central Great Plains. When those trees were cut much larger plains were opened up allowing poor farming practices to let the dustbowl occur during a natural warming cycle.
      Climate and how it cycles is very complicated. Deep green environmentalists need something simple such as CO2 to promote their agenda. They can’t wait around because the fear they need to get control would disappear.

  15. Is this why cloud cover decreases during Forbush decreases? Perhaps the cosmic ray reduction immediately slows the nucleation of VOCs at high altitudes and throws a temporary monkey wrench in cloud creation. Maybe a study of cloud cover around the Amazon rain forest during Forbush events is warranted, it would be neat if the effect could be observed.

  16. “Terpene” identifies a large and diverse class of organic compounds produced by a variety of plants. Well known examples are terpentine and lemon oil.
    Isoprene (C5H8) is the base unit of terpenes. The basic molecular formulae of terpenes are multiples of that, (C5H8)n where n is the number of linked isoprene units.
    Terpenes are hydrophobic VOCs, and will not of themselves form particles or hold onto water molecules. Only when raised by vertical convection currents) to high altitudes where they may encounter ozone are they altered to form oxidized VOCs, which can then gather water molecules and become nuclei for raindrops.

  17. I don’t know about high altitudes, but every day I see how they form at ground level. For calibration, the following video was shot from my living room in Panama at 1200 meters, 9 degrees north looking west at Mount Baru, 3500 meters and the largest mountain on the cordillera. A great view of the thermocline in action. The wind is southerly flowing over the continental divide about 200 meters above us. It has dumped its moisture on the Caribbean side and cooled as it transits the divide.
    By late afternoon, the trees are saturated with moisture and presumably terpenes. The clouds literally boil directly out of the jungle, like a raging forrest fire or the inverse thereof. If you look closely just before the thunderstorm, you can see tornados of cloud spiraling up off of individual trees just upwind of the main “front.” When these flows meet opposing flows from the Pacific, thunderstorms ensue, as in the video.
    The trees operate as pumps, transporting water from the underground aquifers to the atmosphere in the most efficient manner possible according to the Constructal Law. I wonder if more/less moisture/aerosols are transported by this mechanism than by the bubbles in the ocean per unit area?
    As for clear cutting the rain forrest – not to worry. With plenty of sun and 200+ inches of rain per year, the rain forest is an incredibly competitive and fast moving ecosystem. The joke is, when folks arrive from the relative deserts of the north, they plant prissy little gardens like they used to have. If you leave for a week, you can’t find the garden any more. In two weeks, you can’t find your house.
    An interesting question: Is more water transported to the atmosphere by fast growing very dense vines and shrubs, or by mature forest canopy? Same for CO2 consumption. ??
    Bottom line – anyone who says they “know” how could formation in the tropics affects the climate is a liar or fool or both.

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