Some Amazon rainforest regions more resistant to climate change than previously thought

New observational study demonstrates that increasing air dryness does not reduce photosynthesis in certain very wet regions of the Amazon rainforest, contradicting Earth system models that show the opposite


Research News


New York, NY–November 20, 2020–Forests can help mitigate climate change, by taking in carbon dioxide during photosynthesis and storing it in their biomass (tree trunks, roots, etc.). In fact, forests currently take in around 25-30% of our human-generated carbon dioxide (CO2) emissions. Certain rainforest regions, such as the Amazon, store more carbon in their biomass than any other ecosystem or forest but when forests become water-stressed (not enough water in the soil, and/or air is extremely dry), forests will slow down or stop photosynthesis. This leaves more CO2 in the atmosphere, and can also lead to tree mortality.

The current Earth system models used for climate predictions show that the Amazon rainforest is very sensitive to water stress. Since the air in the future is predicted to get warmer and drier with climate change, translating to increased water stress, this could have large implications not just for the forest’s survival, but also for its storage of CO2. If the forest is not able to survive in its current capacity, climate change could greatly accelerate.

Columbia Engineering researchers decided to investigate whether this was true, whether these forests are really as sensitive to water stress as what the models have been showing. In a study published today in Science Advances, they report their discovery that these models have been largely over-estimating water stress in tropical forests.

The team found that, while models show that increases in air dryness greatly diminish photosynthesis rates in certain regions of the Amazon rainforest, the observational data results show the opposite: in certain very wet regions, the forests instead even increase photosynthesis rates in response to drier air.

“To our knowledge, this is the first basin-wide study to demonstrate how–contrary to what models are showing–photosynthesis is in fact increasing in some of the very wet regions of the Amazon rainforest during limited water stress,” said Pierre Gentine, associate professor of earth and environmental engineering and of earth and environmental sciences and affiliated with the Earth Institute. “This increase is linked to atmospheric dryness in addition to radiation and can be largely explained by changes in the photosynthetic capacity of the canopy. As the trees become stressed, they generate more efficient leaves that can more than compensate for water stress.”

Gentine and his former PhD student Julia Green used data from the Intergovernmental Panel on Climate Change’s Coupled Model Intercomparison Project 5 (CMIP5) models and combined them with machine learning techniques to determine what the modeled sensitivity of photosynthesis in the tropical regions of the Americas was to both soil moisture and air dryness. They then performed a similar analysis, this time using observational remote sensing data from satellites in place of the model data, to see how the observational sensitivity compared. To relate their results to smaller-scale processes that could explain them, the team then used flux tower data to understand their results at the canopy and leaf level.

Earlier studies have shown that there are increases in greenness in the Amazon basin at the end of the dry season, when both the soil and air is drier, and some have linked this to increases in photosynthesis. “But before our study, it was still unclear whether these results translated to an effect over a larger region, and they had never been connected to air dryness in addition to light,” Green, who is now a postdoctoral research associate at Le Laboratoire des Sciences du Climat et de l’Environnement in France, explained. “Our results mean that the current models are overestimating carbon losses in the Amazon rainforest due to climate change. Thus, in this particular region, these forests may in fact be able to sustain photosynthesis rates, or even increase it, with some warming and drying in the future.”

Gentine and Green note, however, that this sensitivity was determined using only existing data and, if dryness levels were to increase to levels that are not currently being observed, this could in fact change. Indeed, the researchers found a tipping point for the most severe dryness stress episodes where the forest could not maintain its level of photosynthesis. So, say Gentine and Green, “our findings are certainly not an excuse to not reduce our carbon emissions.”

Gentine and Green are continuing to look at themes related to vegetation water stress in the tropics. Green is currently focusing on developing a water stress indicator using remote sensing data (a dataset that can be used to identify when a forest is under stressful conditions), quantifying the effects of water stress on plant carbon uptake, and relating them to ecosystem traits.

“So much of the scientific research coming out these days is that with climate change, our current ecosystems might not be able to survive, potentially leading to the acceleration of global warming due to feedbacks,” Green added. “It was nice to see that maybe some of our estimates of approaching mortality in the Amazon rainforest may not be quite as dire as we previously thought.”


About the Study

The study is titled “Amazon rainforest photosynthesis increases in response to atmospheric dryness.”

Authors are: J. K. Green 1,2; J. Berry 3; P. Ciais 2; Y. Zhang 1,4; P. Gentine 1,5

1Department of Earth and Environmental Engineering, Columbia Engineering

2Laboratoire des Sciences du Climat et de l’Environnement (LSCE), Gif sur Yvette, France

3Carnegie Institution for Science, Stanford, CA

4Department of Earth and Environmental Sciences, Lawrence Berkeley National Laboratory

5The Earth Institute, Columbia University

The study was supported by NASA Earth and Space Science Fellowship (NNX16AO16).

The authors declare that they have no competing interests.



DOI: 10.1126/sciadv.abb7232

Columbia Engineering

Columbia Engineering, based in New York City, is one of the top engineering schools in the U.S. and one of the oldest in the nation. Also known as The Fu Foundation School of Engineering and Applied Science, the School expands knowledge and advances technology through the pioneering research of its more than 220 faculty, while educating undergraduate and graduate students in a collaborative environment to become leaders informed by a firm foundation in engineering. The School’s faculty are at the center of the University’s cross-disciplinary research, contributing to the Data Science Institute, Earth Institute, Zuckerman Mind Brain Behavior Institute, Precision Medicine Initiative, and the Columbia Nano Initiative. Guided by its strategic vision, “Columbia Engineering for Humanity,” the School aims to translate ideas into innovations that foster a sustainable, healthy, secure, connected, and creative humanity.

From EurekAlert!

39 thoughts on “Some Amazon rainforest regions more resistant to climate change than previously thought

  1. ” Indeed, the researchers found a tipping point for the most severe dryness stress episodes where the forest could not maintain its level of photosynthesis. “

    Seriously? Another tipping point using where the “models on top of models” pseudoscientists used what was probably an unrealistic RCP 8.5 scenario from CMIP5? More delusional pseudoscience masquerading as science.

    They said that with a straight face while acknowledging they failed at modeling photosynthesis and greening. To wit:
    ““Our results mean that the current models are overestimating carbon losses in the Amazon rainforest due to climate change. Thus, in this particular region, these forests may in fact be able to sustain photosynthesis rates, or even increase it, with some warming and drying in the future.””

    Computer models don’t “enlighten” their producers. They merely reflect what they were programmed to do.
    It was the real observations that conflicted with their models that enlightened them, observations that differed from their expected result.

    The only question is will these producers use the real world observation that contradicts to correct their underlying assumptions and thus their claimed “tipping point?”
    Or will they just model ever onwards like a Climate Don Quixote?

    I’m guessing them being another Don Quixote of the Climate Scam because that’s where the grant money lays. One has no future at a climate scam University like ColumbiaU (CommieU) unless you can keep the climate scam going and keep bringing Federal govt grants to feed the system and ultimately your salary.

    • Well Okay. They were using historical calibration runs of climate models. Not future RCP forcing scenarios.
      But I gotta say, this is a real treat where they say for their 2 main data figures: “Stippling in these figures represents regions where at least 6 of the 10 ESMs agree on the sign of the sensitivity displayed.”

      Consensus science 21st Century style.
      Kinda reminds of the movie “Minority Report.” Just throw out the minority of data/models that don’t agree with the majority bias and go with it and call it “Believe in Science.”

    • “contrary to what models are showing–photosynthesis is in fact increasing in some of the very wet regions of the Amazon rainforest during limited water stress”

      Talk about moving the goal posts. Models predict “the Amazon rainforest is very sensitive to water stress”. Nothing controversial there, of course, generally speaking, rainforests are sensitive to water stress. But they only look at “certain very wet regions”, where bit of drying helped and in the Amazon that probably means the forest only flooded half way up the trees. Brilliant insights. Thankyou Captains Obvious.


        • I though the UN Narrative was: more CO2, more heat, more water vapor in the air,
          more greenhouse effect, runaway climate system …
          Here they’re saying models indicate warmer means drier …
          It’s really apparent that they “model” according to the message that they want to get across.
          Pick and choose computer game science.

          • As with all things climastrological, they have causality reversed. They think that deserts are dry because they are hot, whereas they are actually hot (and cold at night) because they are dry.

            With that misunderstanding they therefore think that if a rain forest were to get slightly warmer, it must get drier.

            Climastrology, is there anything they get right?

      • So, you have nothing to counter what was found except mindless baseless suppositories.

        It is well known and MEASURED that enhanced atmospheric CO2 helps ALL plant life. !

        “contrary to what models are showing” … so models yet again PROVEN WRONG by REALITY..

        Models predict .. ROFLMAO !!

        Next !!

    • We are observing an evolution of alarmist dogma. Atmospheric “dryness” and “thirst” are emerging as new terms meant to invoke emotion for support and to make alarmist deception less visible.

      It is antithetical to science to take accurate and precise terms and to substitute visceral meanings for them. But that is how carbon dioxide becomes carbon for example.

    • I used to teach Environmental Science and pointed out every year that coral reefs and rainforests are the most durable and long lasting ecosystems, as, otherwise, they could not have evolved such species interactions and complex food webs. It is ALWAYS hot at the equator, near which these ecosystems are located.

      And, jungle races back at a very high rate after an area has been clear cut for farming and abandoned. The rate is about 50 to 1, such that there is more rainforest now than there was in 1950. And, a big AND, no species have been found to go extinct because, as the jungle charges back in, all kinds of fauna come with it.

      It is the more severe climes, such as tundra and even temperate, that are at risk because the next glacial period will wipe then out and they will have to move toward the equator. Canada will have its clock cleaned be the next ice sheet.

      It is claimed that it takes 10,000 years to produce an inch of topsoil, which is far from true, but it is clear that there is wonderful farming on plenty of topsoil going on in Canada. This is ALL on topsoil produced, from scratch by the way, in the last 10,000 years, with the end of the last glacial period.

      • What a joyous thought! By the time that the glaciers engulf the remnants of New York City, Canada will have long since achieved Truedope’s target of zero CO2 emissions, and a sustainable human population of zero.

        However, there will be a lot more ex-Canadians in Arizona and Florida, probably still voting to make electricity unaffordable.

  2. Last time I looked, plants rely on water to bring to them the nutrients they require to thrive and grow. If the atmosphere becomes drier, presumably translated as less rainfall locally, they have to expand their root systems downwards, laterally or both in order to access the required water and the nutrients it carries. This necessitates additional nutrients, so additional photosynthesis. Excessive dryness means limited nutrients and activity reduces or ceases altogether and the plant dies. Is a model required to understand this?

    • Water loss through leaf stomata opening is the real threat to C3 plants. The soil in amazonia has the soil moisture the plants need if they can balance with the dark cycle photosynthesis needs to exchange the air to keep internal CO2 at levels to avoid photorespiration. Higher CO2 allows the stomata to stay closed longer and have fewer stomata on leaf surfaces thus conserving water by reducing water loss. CO2 measuring towers in these tropical forest areas shows large drops in ground level CO2 concentration as the plants open their stomata to exchange air and draw down ambient CO2 to turn it into sugars. The higher the ambient CO2, the less they have to open stomata, thus reduce water loss as well.

      An educational experiment for kids that can be done in summer in a modestly wet climate is to place a large pane of clear glass over a section of green, well watered grass. Leave it there for 24 hours on a sunny day to the next. Remove it and watch what happens over the next several days. The grass leaves turn yellow and dies. The build up of oxygen and lack of CO2 was toxic. Photorespiration kills when the plants can’t exchange CO2 even if well watered.

      • However, plants source all nutrients via their water intake. Any deficiency or shortfall in the supply of any one nutrient must necessitate the intake of more water to make up the volume required. Since the volume of water taken in must be vented via the stomata to maintain the required water pressure, more stomata may be required to handle the additional volume of water. The example you provide can be the result of an intake blocked, as you suggest, or an exhaust blocked, which is my viewpoint. Any experiment that can have more than one answer is, in my view, inconclusive.

  3. “The current Earth system models used for climate predictions show that the Amazon rainforest is very sensitive to water stress.”

    No. The models ASSUME.

  4. How could anyone just assume that in a warming world that it would get drier? On a world that is mostly water and with computer models predicting the disappearance of the ice caps? Where did they think all the evaporated water is going to go from the warming oceans? Seriously, do they in the climate cult even read their own crap and even try to keep their story straight? I hope there really is global warming, at least slow and steady like it’s been since the last little while and not the rollercoaster it has been since about the time of the Minoans. The world will, on the whole, be warmer, wetter, and very much greener.

    • And, on a molar basis, typically the combustion of fossil fuels releases more water than carbon dioxide.

      Your point regarding climate since the Minoans is on target.

    • A warmer world would mean warmer oceans in time and higher rate of water evaporation. The water contains property of the atmosphere would indeed increase, but evaporation would aim to fill this. Thus more water in the air and more condensation all over depending on weather patterns. It is a cooler world that would make it drier as more of the evaporated water would fall in colder regions and be retained as ice. And there would be less area for land flora and fauna in a colder world.

      That said, global warming and cooling is mostly at night and in the seasons. A warmer climate means slightly less cold nights and longer warm seasons (good for plants) and shorter winters.

      In the late 1970s, at the depth of the latest cold phase, we had a summer heat wave up to 120 deg F on inland Maine—120 million chickens died and the National Guard was called out to remove 1000s of tons of dead bird. It was not that hot again in the next 40 years of Maine summers. The heat wave was weather not climate.

      • Every so often when there has been a cold spell, I have challenged one of my warmist contacts to explain how it fits in with their global warming narrative. Of course, the routine reply is, “Oh, that’s just weather!” My comeback is, “Isn’t it amazing to see how all it takes is a little weather to bet rid of all that terrible heat trapped by the carbon dioxide? But, since all it takes to get rid of it is a little weather, why should I be so concerned?”

  5. I wonder how they can know that the trees are absorbing 25 to 30 per cent of humanity’s CO2 as opposed to the naturally occurring carbon dioxide? Is there some magic molecule marker ?

  6. Complete garbage from the outset…..
    “Since the air in the future is predicted to get warmer and drier with climate change”

    Surely the GHGE *depends* upon *more* water vapour to positively feedback and strengthen the feeble warming effect of CO2 alone

    By their own words, they (repeatedly) damn themselves.
    BTW: Hell is a cold place, not hot as usually cracked up to be

    Other people’s words?
    In the face of the tsunami of junk that is Climate Science, they fail.
    There aren’t The Words.

  7. A few years ago I flew overnight from Santiago, Chile, to Madrid, Spain, crossing over the Amazon Basin. No lights at night! Towns and highways south and north of a 600 mile stretch, but in the middle, nada. The idea that the Amazon Basin has become infested with people, cutting down the jungle and growing things, is difficult to imagine given this view. Who thinks a jungle will have trouble with photosynthesis? Or snakes, for that matter?

  8. What a beauty;

    “ Gentine and Green note, however, that this sensitivity was determined using only existing data and, if dryness levels were to increase to levels that are not currently being observed, this could in fact change”

    So this is how you keep your funding these days, when your research demonstrates that there is actually no problem and things are not as bad as assumed beforehand just state that things could get worse later you’re all good to go.

    This seems to be the way all the scaremongers overcome the fatal flaw of climate science, i.e. that the ‘existing data’ simply doesn’t support the catastrophic narrative.

    Anyway, this is the second article in two days that ‘denies’ the core of climate catastrophe models, the so called water feedback loop on temperature (More heat => more evaporation => more heat, repeat until doomsday). Is there a breakdown of climate science happening?

    Stay sane,


  9. Earth system models

    That’s really all I needed to read. Nobody has a model of all the Earth’s systems….why? Because it is too complex. It’s like proclaiming we know exactly how the human brain works. We don’t. We know bits and pieces and but this just illustrates when you try to put those bits and pieces together, they only fit on 1 corner.

    Instead of claiming they know all and are now only discovering it might not be as dire—why not say, “hey, we’ve got another piece to the puzzle, but we still need to know more before we can put it together”.

  10. Oh puhleeese. What utter codswallop. If the trees are responding to anything, it is the increased CO2, which makes them more drought-resistant. If only trees could talk, they’d be screaming “We need MORE CO2, not LESS!
    Stupid trees. What do they know?

  11. May not amount to much but have we reached the bottom of the negativity barrel? No where to go but up?

    “Our results show that land surface models used for climate projections are overestimating atmospheric water stress in the tropical rainforests due in large part to the absence of dynamic vegetation biogeochemistry, thus misrepresenting the carbon uptake of these carbon-rich forests”

    Something called field work, checking on things, problem solving, we used to do more of it, lots of examples. It’s called “cross-disciplinary research.”

  12. “Since the air in the future is predicted to get warmer and drier with climate change”
    This statement is NOT what climatologists generally state….higher surface temperature….higher evaporation primarily off oceans….more rainfall is the result…..although they are somewhat inconsistent depending on which media reporter is interviewing them….

  13. Others caught this statement, but it’s early here in calgary
    “ the researchers found a tipping point for the most severe dryness stress episodes where the forest could not maintain its level of photosynthesis“.

    All plants eventually die if they don’t get water, as my wife can demonstrate when I go away for long business trips.

    But of course, warmer means wetter, colder means drier.
    Warmer, is there any evidence the Amazon was stressed during the Holocene optimum?
    Cooler, how did the Amazon do during the last ice age?

    Of course, CO2 is fertilizer, greening of the earth is an undeniable phenomenon
    Are they really have to speculate about the increased greening they saw in dry season?


  14. Ho hum, we have empirical evidence for the biggest experiment ever that changing climate does NOT wipe out life on earth. This is an incontrivertible truth. Will it have effects- yes. Does it wipe out forests or kill coral? Absolutely not as proven multiple times in our history.
    Honestly, we need to start devoting our actual scientific powers to helping humanity survive and stop the pseudo science of Klimate change for the junk that it is- junk with evil intent of controlling humanity by those oh so benevolent powers like Al Gore who only want the best for humanity (sarc). The same Al Gore of fossil fuel wealth and lavish lifestyle hypocrisy. Just picked AG out of numerous Klimate hypocrites…

  15. From the above article’s introductory paragraph: “. . . contradicting Earth system models that show the opposite”.

    Hmmm, let’s see . . . where else have I’ve heard that same phrase applied?

  16. climate change is NOT a force it has no power and has never caused any weather event…..the climate is a set of statistics, the average weather stats from the previous 30 years for a given area.

  17. We have seen El Nino episodes cause widespread drought in the Amazon, and El Nino conditions normally increase during centennial solar minima.

    • We are currently in a strong La Nina (opposite of El Nino), with record numbers of hurricanes in the Atlantic. Some of those “tropical waves” that are blown inland by the northeast trade winds along the northern coasts of South America are likely bringing increased rainfall to the Amazon rain forest.

  18. Complete “let’s find some evidence/model to validate a conclusion. Who funds this drivel? What a waste of time, money and human endeavor.

  19. Photosynthesis requires CO2, water, and sunlight. A slight decrease in humidity and/or rainfall would not cause the rain forest to completely dry out, but it would increase the amount of sunlight received, so that photosynthesis rates would increase.

  20. We know the Amazon rainforests were clearly hurt by the cold, low-CO2 glacial periods — greatly reduced in size and replaced in large, former areas by savannas.

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