Study: Urban backyards contribute almost as much CO2 as much as cars and buildings

From the “mulch your way to a warmer planet” department and Boston University:

Stephen Decina, Boston University PhD student, measures carbon dioxide being released from the soil using an automated soil carbon dioxide efflux system. The equipment, which is controlled with a smartphone, passes air through an infrared gas analyzer and measures the concentration of carbon dioxide accumulation over time.

Stephen Decina, Boston University PhD student, measures carbon dioxide being released from the soil using an automated soil carbon dioxide efflux system. The equipment, which is controlled with a smartphone, passes air through an infrared gas analyzer and measures the concentration of carbon dioxide accumulation over time.

Urban soils release surprising amounts of carbon dioxide
Tracking biological emissions will allow more accurate assessments of climate action programs

(Boston) – Feb. 23, 2016 – In the concrete jungle at the core of a city, carbon dioxide (CO2) emissions are dominated by the fossil fuels burned by the dense concentrations of cars and buildings. Boston University researchers now have shown, however, that in metropolitan areas surrounding the city core, plant roots and decomposing organic material in soil give off enough CO2 , in a process termed “soil respiration”, to make an unexpectedly great contribution to total emissions.

In fact, analyzing CO2 released from soil respiration at 15 sites across greater Boston, the BU scientists found that during the growing season, releases of the greenhouse gas from soil may approach those of fossil fuels in dense residential areas. The first study of urban soil CO2 to reach this wide scale and to integrate a high-resolution model of both soil respiration and local fossil fuel emissions, the research will help to improve assessments of climate action programs.

“Very close to this concrete jungle downtown, where you have a lot of fossil fuel emissions and no soil, you have residential areas that have lower fossil fuel emissions and a whole lot of soil,” says Stephen Decina, a doctoral student and lead author on a paper published today in the journal Environmental Pollution. “Over the growing season, CO2 emissions from soil respiration are almost 75 percent of the fossil fuel emissions in those areas. In some places, they’re actually higher than fossil fuel emissions.”

“These biological fluxes are much larger than you’d expect,” says Lucy Hutyra, Associate Professor of Earth & Environment and coauthor on the paper. “In our efforts to monitor, verify, and reduce greenhouse gas emissions in cities, we really need to pay attention to this.”

Decina and his colleagues measured the emission of CO2 from the same patches of soil around metropolitan Boston every two weeks during the growing season when releases of the gas are highest and measurements are not impeded by snow.

“We found that the average rate of CO2 coming out of the soil is highest in landscaped areas such as gardens, followed by areas with a lawn, and it is lowest in the urban forests,” he says.

These rates of CO2 release generally reflect the level of human interventions at each location. “People often manage their flower beds more than they do their lawns, and in general they leave their forests alone,” Decina points out.

“When people mulch their landscaped areas or fertilize their lawns, they’re putting out yummy fresh highly decomposable carbon that soil microbes can use,” says Pamela Templer, Associate Professor of Biology. “And that’s stimulating microbial growth and loss of CO2 out of these urban soils.”

The scientists emphasize that they are not recommending that residents stop mulching or fertilizing their yards. Rather, this study highlights the high soil respiration rates associated with those activities.

Their findings will help in evaluation of climate action programs such as Boston’s Greenovate, which aim to reduce greenhouse gas emissions from cities like Boston. “Studies that rely on satellite measurements of CO2 don’t distinguish between human-made and biological emissions. Our study shows that CO2 fluxes from soils, which come from biology (microbes and roots), can make a significant contribution to total CO2 emissions from a city like Boston,” Templer says.

“If you assume all the CO2 emissions in the city are coming from man-made sources like cars and buildings, and you don’t account for what the soils are doing, then you don’t have the correct information to assess whether your climate plan is actually reducing emissions,” Decina says.

“For a long time we’ve had the perception that biology doesn’t matter in cities, because it seems that there’s so little of it,” Hutyra says. “But we show that biological sources are contributing a large amount of CO2.”

The BU team is going on to analyze urban flows of nitrogen, which are generated by cars, factories and farms and then deposited in high rates by precipitation or air particles. “Nitrogen is a limiting nutrient,” Templer says. “A small amount of nitrogen from rain helps plants (whether they be in landscaped areas or forests) grow more. But too much nitrogen can be a bad thing for soils, waterways and human health.”

At a broader level, the researchers are questioning whether urban ecosystems require scientists to re-think traditional models of nutrient flows.

“Does a tree in the city do more or less than a tree outside the city?” Hutyra asks. “That city tree is growing in a very different environment. It has extra CO2, warmer temperatures, lots of nitrogen, lots of dogs, salt on the road, pipes that are leaking sewage and feeding it all sorts of nutrients, ozone, people cutting off its branches, and a whole suite of direct intentional and unintentional management.”

“We’re increasingly recognizing the importance of coupled human-natural ecosystems research–understanding not just how nature works, or how humans affect nature, but how that all feeds back to one another,” Templer says.

Investigating these phenomena in cities is not always a picnic, the researchers note.

One challenge in urban ecology is that researchers can’t expect their equipment to stay undisturbed, says Decina, which is one reason why almost all of the CO2 study sites were in residential backyards.

“This fieldwork is different than the kind that we’re used to, out in the forest worried about bears,” he adds. “In the city you don’t have to carry bear spray with you, but curious or angry humans can often be more disruptive to a research site than a curious or angry bear.”

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111 thoughts on “Study: Urban backyards contribute almost as much CO2 as much as cars and buildings

    • What about the Bostonians who breathe (i.e. the live ones). Don’t they emit CO2? Has that been factored in? What about their pet dogs and pussycats? Don’t they emit Co2 too? Help! Where does it all end?

      • Any high concentration of carbon based life forms will emit CO2 when it decays.
        Is there any surprise that human ecology creates the equivalent UHI due to decay.
        Think about it. All the garbage, bodies, etc concentrated around the cities.
        Decomposing and obeying the laws of thermodynamics.
        Who woulda thunk it?

  1. CO2 that comes from decomposing organic matter has carbon that was in atmospheric CO2 that was removed from the atmosphere by plants. If a city is a year-round net source of CO2 of biological origin, then the city is importing biological carbon from outside the city (and/or losing biomass – less likely a dominant factor).

  2. None of these environmentalist have had any training or took any Biology classes during their education. No wonder they are so surprised at their results. Look at the OCO2 map generated from NASA. The highest concentrations were over the Amazon rainforest & they attributed it to mass burnings. I was laughing for months over that. What a bunch of educated MORONS!

      • Yes, but that is only from one month, there are graphs for a full year which gives a better idea of what happens in the real world…
        Here a lot more data visualized:
        https://wattsupwiththat.com/2015/10/04/finally-visualized-oco2-satellite-data-showing-global-carbon-dioxide-concentrations/
        and more discussion at:
        https://wattsupwiththat.com/2015/11/04/oco-2-orbiting-carbon-observatory-2-the-mission-has-released-an-animation/
        and the animation by NASA:

        Keep in mind the scales and that human emissions are only ~4 ppmv/year of which half remains in the atmosphere (in quantity), or 0.01 ppmv/day, not even detectable by the satellite, except for dense spots and longer measurement times…

      • Ferdinand:

        You say

        Keep in mind the scales and that human emissions are only ~4 ppmv/year of which half remains in the atmosphere (in quantity), or 0.01 ppmv/day, not even detectable by the satellite, except for dense spots and longer measurement times…

        It is you who fails to “keep in mind” that the human emissions are so small and insignificant that they are “not even detectable by the satellite” because natural variations are so very much larger.

        I not only keep it in mind, I also keep pointing out that the human emissions are that small and insignificant And I don’t make assertions about “longer measurement times” that don’t exist.

        If, as you assert, the human emissions were overloading the ‘sinks’ to cause the observed rise in atmospheric CO2 concentration then the sites of human emissions would have highest atmospheric CO2 concentration: they don’t. The OCO-2 plots indicate that the human emissions are sequestered near to their emission sites because those sites are seen to not overload.

        The OCO-2 data does not categorically demonstrate the human emissions are not causing the observed rise in atmospheric CO2 concentration. But it does categorically demonstrate that you – and others – are wrong when you claim the human emissions are overloading the ‘sinks’ so “half remains in the atmosphere” to cause the observed rise in atmospheric CO2 concentration.

        Richard

      • Richard,

        If you don’t understand the difference between momentary sinks and sources, which are huge, and long term one-way addition, which is small, then we can’t even have a discussion…

        The measured increase in the atmosphere is about 2 ppmv/year, no matter the source. That is less than 0.01 ppmv/day. The satellite can detect about 0.1 ppmv CO2 differences, somewhat better as the satellite can focus on specific areas during a longer time.

        Anyway, the satellite can’t detect the location of the increase in the atmosphere, as its resolution is not good enough, except if concentrated in certain areas.

      • “If you don’t understand the difference between momentary sinks and sources, which are huge, and long term one-way addition, which is small, then we can’t even have a discussion…”

        You do not know that other sources have net zero impact, you merely assert it. It is an arbitrary constraint you have levied which has no empirical backing. It is how you want things to be, not how they demonstrably are.

      • Bart,

        You do not know that other sources have net zero impact, you merely assert it.

        The satellite can’t detect local CO2 changes of less than 0.1 ppmv, neither for human emissions nor natural emissions. Except if focused on areas of huge concentration by humans or nature. A change of 2 ppmv/year, whatever the cause, will be a huge challenge for the satellite, if it is widespread (natural) or even concentrated in smaller areas (human)…

      • By ppm/v from human co2 production is higher than 4 ppm. It’s anywhere from 5 to 8 ppm. The current 2 ppm from human production that makes its way into the atmosphere … there is something wrong. It should be at least 6 ppm with an increase of 3 ppm. By volume 6 BMT raises the ppm by 1 providing none of the 6 BMT is sunk.

    • I just noticed that the results of that original OCO-2 graphic for Oct-Nov 2014 is totally different from that shown in the NASA animation. All of the red and orange are gone!

    • CO2 is good, not evil, but the MSM portrays is almost as if it wassatan himself… on the other hand smog (to be more precise carbon MONOxide, the CO) is what we should be fighting against.

  3. I’m ready for my green subsidy to astroturf my yard. Then I’ll sell the lawnmower and reap a profit as long as I get in early!

    • No need Jim. Just get rid of the mulching mower, rake up all clippings, dig a 50 foot hole in the ground and bury the clippings there. When full, cover with clay and start another hole.

      • Actually my well survey shows a 9 ft layer of clay under the first 30 feet of sand. Just so as not to leave our engineer friends dangling, then there was about 10 feet of mixed gravel and shell under the clay then limestone in which they found my pocket of water 55-65 feet down. As Florida water goes, it’s pretty good, very tiny amount of iron and no sulfur.

      • Well heck. You must live in a different part of Florida. Clay? My part time part time Ft has fossiliferous porous ‘coral rock’ all the way down to limestone ‘bedrock’ about 80 feet below. Heck, clay. You must be up near Georgia, where all that clay weathered from. Mountains, and all that.

        [The mods hope both your right full-time foot and left full-time foot have the proper calciferous deposits all the way down through each of their bony masses …. .mod]

      • Sarasota County, south central west coast. The most of central part of Florida has a layer of clay just above the limestone of the Florida Aquifer that seals the aquifer from ground water. The only place that does not have clay is the Green Swamp in Polk County where the water seeps down to replenish the aquifer. So my well water comes from far away slowly working its way west through the limestone. There are 3 levels of aquifer in my area at depths of 50-70 feet, 150 feet and 400 feet.

  4. And they did not get environmental or climate change impact studies performed on that backyard. Send in the drones.

  5. “These biological fluxes are much larger than you’d expect,”

    I love being told what I expect. (insert Judge Judy’s shrill condemnation “Don’t tell me what I expect!”)

    Just another inside look at the serial projection affliction rampant in climate sc!ence.

  6. The CO2 is probably going in the wrong direction through the machine. Basic science indicates and I have it on good authority that gravity is still working and a CO2 molecule is still heavier than air.
    A classic example is the frozen CO2 released on stage during a concert. Does it go up?
    With the CO2 allegedly going upwards I guess we will have to see what transpires.

  7. Good God, did they miss kindergarten? More CO2 = more plant growth = more support for wildlife. Any CO2 released from the soil would be sucked up by plants and trees.

    However, lawns are considered a green desert in the gardening/wildlife world, they don’t provide nearly the nutrition that native plants and grasses do, plus you have to put a lot of chemicals on them and mow a lot for them to look nice. A switch to native grasses is much healthier all around, as long as you don’t have a golf course.

    That said, I’ve yet to convince my husband to give up his lawn, even though it’s only used by the dogs to crap on.

    • Sorry Lorraine, I’m probably like your husband, hyper attentive to the lawn. However, unlike my neighbor who has a service to manicure her lawn with nail clippers, has a service to spray chemicals designed to “weed and feed” her lawn, and has to have every scrap of clippings, leaves and debris removed; I’m quite old school.
      I use a mulching mower to push the clippings back into the lawn. I shred and compost the (abundant) leaves for use in my garden beds, and VERY seldom use chemicals on the lawn (I’ll admit to the use of a little Round-Up to stop the grass/weeds from coming out of the cracks in the patio). It’s taken about 3 years on this lawn, but I now have a nice self sustaining cycle of soil enrichment going and my gardens are producing some of the nicest tomatoes, peppers, asparagus, raspberries, blackberries, and even potatoes in the neighborhood. I just waiting on the apple trees to mature now.
      My reward isn’t “saving the earth”, but the flavor of real homegrown veggies and fruits instead of the mass produced stuff at the local grocer.
      ON THE OTHER HAND, I was called tonight by a survey out of Cambridge, MA about my lawn habits and apparently I’m one of the “greenest” households in the area. That was a surprise to me. I’m not trying to be green, just doing what my father and grandfather did to get “good eats”.

      Jake

  8. This means that CO2 cycling in the soil might contribute significantly to the annual cyclic variations (which nobody ever wants to mention) seen in the Keeling curve which show that the atmospheric CO2 levels can drop 5-7 ppm in only a few months

    • tadchem:

      “(which nobody ever wants to mention)”? Say what!?
      People – including me – “want to mention” it, but few want to hear.

      I and others have been shouting about it for many years; e.g. in
      Rorsch A, Courtney RS & Thoenes D, ‘The Interaction of Climate Change and the Carbon Dioxide Cycle’ E&E v16no2 (2005)

      In that 2005 paper we wrote

      Any assessment of the causes of the rise of atmospheric CO2 concentration over a period of years requires assessment of the changes that occur each year (because the annual increase to CO2 in the atmosphere is the residual of the seasonal changes to CO2 in the atmosphere).

      and of direct pertinence to your point

      The natural fluctuation of the excess consumption (i.e. consumption processes 1 and 3 minus production processes 2 and 4) is at least 6 ppmv (which corresponds to 12 GtC) in 4 months (see Figure 2). This is more than 100 times the yearly increase of human production, which strongly suggests that the dynamics of the natural processes here listed 1-5 can cope easily with the human production of CO2.

      emphasis added, RSC

      Richard

    • tadchem,

      Soil bacteria and the decomposing of fallen leaves, stems, dead wood,… certainly are part of the seasonal cycle, where they are more active in summer than in winter (but even in winter under a snow deck, that goes on). The point is that the overall balance of photosynthesis at one side and decay/feed/food on the other side shows a small, but growing net sink: more CO2 is taken out of the atmosphere than is released by decay from bacteria, molds, insects and animals, including humans…

      That can be calculated from the oxygen balance: burning fossil fuels uses oxygen, which can be calculated from sales and burning efficiency for the different fuels. The measurements show that somewhat less oxygen is used than calculated. That means that the biosphere as a whole is a net producer of oxygen and thus a net sink for CO2. See:
      http://science.sciencemag.org/content/287/5462/2467.short
      and
      http://www.bowdoin.edu/~mbattle/papers_posters_and_talks/BenderGBC2005.pdf

      Thus while interesting to know what causes the seasonal swings which is mainly by the NH vegetation, it is not the cause of the CO2 increase in the atmosphere…

  9. “If you assume all the CO2 emissions in the city are coming from man-made sources like cars and buildings, and you don’t account for what the soils are doing, then you don’t have the correct information to assess whether your climate plan is actually reducing emissions,” Decina says.

    My climate plan?

    Who actually does crap like this?

    • Hold on there a minute. There are household budget planners, estate planners and retirement planners so why not a climate planner. I am sure that those with feelings of environmental guilt will gladly shell out a few thousand bucks to a have plan drawn up.

      • Hey, universities can even sell on line courses in becoming a Certified Climate Planner, the States could make you get a license for a fee and require continuing education classes. More people can get a piece of the climate pie this way.

      • And thus would the educational ‘debt crisis’ where unqualified students take on massive debt to try to educationally qualify for that to which they were obviously unsuited (by objective standards like grades and aptitude exams) be rendered into perpetuity.

    • after reading this crud
      I would be putting beartraps to remove the pests aka researchers.
      I am ragingly angry
      how much of this drivel are we supposed to tolerate?
      enough and more than enough..
      theyre lucky they are a ocean away from me right now!

    • All mulching is carbon neutral as what you add to the soil and decomposes was taken out of the atmosphere some months to decades before…

      Averaged over a few decades, there is certainly no release of extra CO2, only a (small) sink for what remains in/on the soil as non/hardly-biodegradable in the form of peat, humus, browncoal and ultimately coal…

  10. These guys may be on to something, not just the micro level of scolding home gardeners for applying mulch applying mulch and fertilizer but in the global carbon balance.
    Salby and others are advancing the notion that even the increase in atmospheric CO2 — the Keeling Curve — is driven by natural processes instead of human emissions.
    One critic of Salby who appears to have some knowledge about carbon balance, commentator “M” on Judith Curry’s blog on August 29, 2011, pointed out that Salby’s linear-correlational model between global temperature and net CO2 emissions does not take into account non-linear ocean chemistry that tends to keep CO2 in the atmosphere. Even taking into account this Revelle buffer, Revelle and Suess in 1957 suggested that the ocean CO2 reservoir is vast, and human emissions could not account for all the increase at that earlier date in CO2, taking into account radiocarbon ages of marine life and ocean water.
    Taking into account Revelle’s mechanism where ocean water resists uptake of CO2 from the air through the complexities of ocean carbonate chemistry, and using a simple 2-compartment model for mixing of the surface and deep ocean layers, and using a Salby-inspired terrestrial model of absorption of CO2 from plants being proportional CO2 concentration, soil emission of CO2 being proportional to temperature, I have devised a carbon balance in an Excel spreadsheet that predicts the Keeling curve with that 50 percent of anthropogenic increase not absorbed in sinks accounting for nearly all the increase in the atmosphere. It also matches the changes in atmospheric carbon isotopes as well as Revelle’s radiocarbon shell and ocean water ages, not to mention the recent atmospheric O2 depletion data. It matches the “bomb test” radiocarbon extinction curves spot-on.
    This model, however, does not match the large fluctuations in net atmospheric CO2 emission that correlate with surface temperature. When I increase both the CO2 uptake of plants and the CO2 emission from dead plants in the soils, I match all of the above trends as well as the fluctuation in net CO2 emission with temperature. But now, only about half the increase in CO2 comes from human emissions, with the remaining part accounted for, yes, it has gotten warmer over the 20th century and this is stimulating soil emission of CO2.
    Not only that, this model gives very rapid (time constant around 20-25 years) extinction of the atmospheric increase. That is, were we to suddenly stop emitting CO2 and were the temperature to return to the early 20th century value, the atmospheric CO2 concentration would be rapidly pulled down to the pre-industrial values.

    • Paul Milenkovic,

      Near all of the increase is from human emissions, temperature is good for ~16 ppmv/°C for the (dynamic) equilibrium between oceans and atmosphere per Henry’s law for the solubility of CO2 in seawater, confirmed by over three million measurements from the oceans…
      Vegetation is a net sink for CO2, based on the oxygen balance and confirmed by satellite measurements: the earth is greening.

      The “large” variations in the year by year rate of change are peanuts (+/- 1.5 ppmv) around the trend of +80 ppmv in the past 55 years and +160 ppmv human emissions in the same period. These variations zero out over 1-3 years time and get negative over longer periods.
      Indeed near all the variability is caused by the temperature (and precipitation) influence on (tropical) vegetation, but the increasing trend is NOT caused by vegetation, as vegetation is a net, growing sink for CO2…

      The decay rate of any extra CO2 in the atmosphere is slightly over 50 years, based on emissions and net sink rate. The 14C bomb curve decays much faster, because that is not only a matter of mass, but also a matter of concentration: What goes into the deep oceans is the current isotopic composition, what comes out is the isotopic composition of ~1000 years ago, long before the bomb tests. Which makes that the 14C/12C ratio decays much faster than the removal of any extra 12CO2 mass above equilibrium.

      That humans are the main cause of the increase fits all observations:
      http://www.ferdinand-engelbeen.be/klimaat/co2_origin.html
      That you can fit the increase and variability with a combination of human emissions and temperature:
      http://www.ferdinand-engelbeen.be/klimaat/co2_variability.html#The_variability

      • Ferdinand, the variation is natural, the trend is human, but you have to account for all of the variation, not just Henry’s law and the oceans. Soils worldwide provide 60 gtc/yr to the carbon cycle, six times human input. Soils are not vegetation. Vegetation is a sink. Soils are a source.

        They have not changed very much compared to human input. They speed up as it warms. Contrary to the implication of the post, atmospheric pCO2 increase resists soil metabolism the same way it resists ocean outgassing, but the purely physicochemical resistance is no match for the possessed determination of life forms either in the soil or in the ocean.

      • gymnosperm,

        CO2 released from soil bacteria and the destruction of dead plants is independent of the CO2 level in the atmosphere, it indeed mainly depends of temperature and moisture. The same for photosynthesis, where the 30% increase in CO2 only gives 1.5% increase in more uptake worldwide in the biosphere, as other necessities like water, nutrients, minerals,… also are limiting.

        Soils are a net source, but the soil bacteria only can release CO2 from carbon species which first were made out of atmospheric CO2 by photosynthesis: fallen leaves, stems, roots and from living plants: sugars released by the roots.
        Taking into account the full cycle, the net balance is slightly more uptake via photosynthesis than release from soil bacteria and the decay of dead plant material at the surface.

      • “That you can fit the increase and variability with a combination of human emissions and temperature”
        That looks not even like a coincidence.
        “The decay rate of any extra CO2 in the atmosphere is slightly over 50 years”
        So what?

      • Ferdinand Engelbeen:

        You say of the continuing rise of atmospheric CO2 concentration;

        That humans are the main cause of the increase fits all observations:
        http://www.ferdinand-engelbeen.be/klimaat/co2_origin.html

        NO!
        Your narrative is refuted by the OCO-2 satellite data (see above here).
        Also, the direct indication of atmospheric carbon isotope changes is that nature (n.b. NOT “humans”) is the “main cause” but the possibility of ‘dilution’ prevents this direct indication refuting that humans may be the main cause.

        You also say

        That you can fit the increase and variability with a combination of human emissions and temperature:
        http://www.ferdinand-engelbeen.be/klimaat/co2_variability.html#The_variability

        So what!? Almost anything fits.

        As you know, in 2005 Arthur Rorsch, Dick Thoenes and I published a paper that demonstrated almost any mechanism can be modeled to provide a fit between global temperature and atmospheric CO2 concentration as measured at Mauna Loa
        ref. Rorsch A, Courtney RS & Thoenes D, ‘The Interaction of Climate Change and the Carbon Dioxide Cycle’ E&E v16no2 (2005).

        We generated six models three of which assumed a significant affect of the human emission and the other three assumed no affect of the anthropogenic emission. Other models are probably also possible. Each of our six models matches the Mauna Loa CO2 data without use of any ‘fudge factor’ such as the 4-year smoothing the IPCC uses to get its model to agree with the data.

        Data that fits all the possible causes is not evidence for the true cause. Data that only fits the true cause would be evidence of the true cause.

        Richard

      • Richard,

        Only humans as source of the CO2 increase in the atmosphere fits all observations, all other theories of what are mathematically possible causes violate one or more observations, including 5 of the 6 models from your and Arthur’s and Dick’s work. Bart’s solution even violates every known observation…

        I always learned that if a theory violates even one observation, the theory is wrong…

      • Rainer Bensch,

        Human emissions are about twice the increase measured in the atmosphere and show very little variability, the latter not even detectable at Mauna Loa. Temperature shows a lot of variability and little trend. CO2 in the atmosphere shows a huge trend and some small variability around the trend. Thus the combination of human emissions and temperature variability explains both the trend and the variability of CO2 in the atmosphere.

        Most theories of a non-human cause are based on the derivatives: the variability in year-by-year CO2 rate of change follows the temperature rate of change with an about pi/2 lag. But by taking the derivatives, you effectively remove much of the trend in the derivatives, which is zero for temperature and slightly linear upward for emissions and CO2 in the atmosphere, due to the slightly quadratic increase in emissions over time.
        Because of the huge fit in variability between temperature and CO2 rate of change, many think that temperature is responsible for the full/most of the CO2 increase, but that can’t be true, as most variability is caused by the response of (tropical) vegetation to temperature (Pinatubo, El Niño), but vegetation is a net sink for CO2 over periods longer than 1-3 years…

        The 50+ years is important for the decay rate of the excess CO2 (if necessary at all…): it is fast enough for nature that CO2 follows the glacial/interglacial temperature changes, but not fast enough to remove human emissions in the same year as emitted…

      • “…all other theories of what are mathematically possible causes violate one or more observations…”

        Nonsense. They only violate your interpretations of the observations. But, your interpretations are not unique.

        “…as most variability is caused by the response of (tropical) vegetation to temperature (Pinatubo, El Niño), but vegetation is a net sink for CO2 over periods longer than 1-3 years…”

        This is merely an assertion.

      • Bart,

        There is no interpretation of observations necessary: if your theory says that the oceans are the main source of the increase in the atmosphere and all observations (over 3 million samples of pCO2 differences, 13C/12C ratio decline, 14C decline, DIC increase, pH drop,…) show that the oceans are net sinks for CO2…

        Moreover, you have not one observation that supports your theory which implies a fourfold increase in natural turnover 1959-2013…

      • Bart:

        This is merely an assertion.

        Supported by the data:

        Parallel variations of CO2 and δ13C are caused by the oceans.
        Opposite variations of CO2 and δ13C are caused by vegetation.

        Vegetation is a proven, increasing sink for CO2, at least since 1990, based on the oxygen balance…

      • The variation in “net CO2 emission” is addressing the fluctuation in the slope of the Keeling atmospheric CO2 curve. There are well-known enormous fluctuations in the slope of that curve on a seasonal scale. These slopes dwarf anything in the multi-decade trend, but since they are periodic and regular, they don’t change the overall trend very much.

        There are also year-to-year fluctuations that are large in comparison to net human emissions, which are not expected to be fluctuating that much. There are booms and busts in human activity, but these are small percentage changes in overall industrial and other activity. Yes these year-to-year fluctuations average out and result in minor variability in the Keeling curve when you “eyeball” it. But these fluctuations speak to exchanges of carbon between reservoirs that are large compared to human emissions, where even small mismatches in these exchanges could account for increases in the Keeling curve — in the absence of human emissions.

        The large multi-year fluctuations in the slope of the Keeling curve is not something one can sweep under the rug, even if it goes away when you look at that curve while squinting. These fluctuations speak to large exchanges between carbon reservoirs that we are only beginning to get data on, such as with the soil emission measurements we are commenting upon.

      • “The decay rate of any extra CO2 in the atmosphere is slightly over 50 years”

        Your answer:
        “The 50+ years is important for the decay rate of the excess CO2 (if necessary at all…): it is fast enough for nature that CO2 follows the glacial/interglacial temperature changes, but not fast enough to remove human emissions in the same year as emitted…”

        Again: S o w h a t ?

      • Paul Milenkovic,

        I think we do agree that the seasonal changes are huge, but have little effect on the yearly increase, the more that vegetation is responsible for most of the (NH) seasonal change, but not responsible for the increase. In this case, higher temperatures give more CO2 uptake, preferably 12CO2 and thus an increase of δ13C in the atmosphere. Decaying leaves in fall/winter/early spring have the opposite effect:

        The year by year variability also is caused by (tropical) vegetation, but opposite to the seasonal changes in the NH: higher temperatures give more CO2 (less uptake) and lower δ13C (more decay):

        As you can see, the year by year variability is in the sink rate, not the source rate, where nature was always a net sink in the past 55 years. While the seasonal exchanges are huge ~50 GtC in and out the ocean surface, ~60 GtC out and in vegetation (in counter current), the variability after a full seasonal cycle is only half human emissions and the average net sink rate also half the emissions.
        Again, most of the variability is from vegetation, but as vegetation is a net, growing sink for CO2, the variability and the slope have different causes…

      • Ferdinand Englebeen:

        I am with you that Net CO2 Emissions (derivative of the Keeling curve) – Human Emissions (estimated from assays and surveys of human activity) = Net CO2 Sink (which I agree fluctuates but hasn’t in recent times crossed the zero level and become a net source).

        You don’t know that there isn’t a large baseline natural emission that is in homeostatic balance with a large baseline sink. Such a thing “washes out” of all of the carbon balances, people don’t see it, so it isn’t there. It won’t show up in the recent atmospheric O2 curves — they only give you the partition between the inorganic (largely ocean carbonates) and organic sinks, they don’t tell you that there could be large fluxes out of organic reservoirs (soil decay) in balance with large fluxes back into organic reservoirs (living plants).

        But what we do know that there is a strong correlation between global temperature measures (take your pick, I guess) and net CO2 emission. What is also claimed is that over the course of the 20th century, global temperature has been rising. Many people around here dispute that it has been rising as much as claimed, or that the temperature change rises and levels off (the early 21st century “pause”, other 20th century “pauses’).

        What temperature records we do have, however, show a strong correlation with net CO2 emission (and hence the net CO2 sink as human emission does not fluctuate anything like this, as your plots show), and Salby claims this to be the case at “all time scales.”

        What Salby further claims that if the fluctuations in global temperature cause the fluctuations in net emissions, these fluctuations are riding on top of a baseline warming over the 20th century, and this warming should be contributing by the same causal mechanism to a strong rise on net emissions over the course of the 20th century, so much so it is these warming-driven emissions that are contributing the lion’s share of the Keeling curve CO2 increase and the human-sourced emissions must be lost somewhere in the baseline sinks.

        In other words, the Great 20th Century Intensification of Fossil Fuel Usage just happens to be at the same time as a century-long Climatic Warming. In the Darwin Debates terms, Adam was spontaneously created, and he just happened to have a navel even though he was never connected to a placenta supplying sustenance from his mother in utero because he didn’t have human parents.

        I am saying that Dr. Salby is at least partly wrong — he is using a linear correlational model in ignorance of the physics, where the ocean uptake is not a linear Henry’s law relationship but the highly non-linear Revelle law (see Revelle and Suess (1957) ). My model splits the difference between Callendar’s hypothesis, that almost all the CO2 increase is what is left of the human contribution after half goes into sinks, and Salby’s claim, that nearly all the human contribution would end up in sinks if there wasn’t such a strong natural thermal component to net emission.

        Ferdinand Englebeen claims that the temperature stimulation of CO2 emission washes out at a fairly short time scale because that is what tropical soils do whereas Paul Milenkovic is claiming that it washes out over a somewhat longer time scale, and that the mechanism for this is the manner in which the non-linear reaction rate-with-concentration of the ocean carbonate system operates, whereas Murry Salby claims that it doesn’t wash out over any near-term time scale.

        What I know if that if I take a very simple model of the CO2 of terrestrial biosphere emissions and sinks, net emission is proportional to temperature above a baseline level, net absorption in proportional to CO2 concentration (yeah, yeah nitrogen and trace minerals and all of that, but there is evidence to suggest that CO2 supply is a rate-limiting factor in plant growth), model the non-linear update of CO2 by ocean water, and tune the terrestrial source-sink balance to match the Keeling curve and the net emission fluctuations with global temperature, suddenly, I start matching everything — the Keeling curve, the temperature-net emission correlation, the atmospheric O2 concentration curves, the C13 curve, the Bomb Test C14 extinction curve, Revelle and Suess ocean water and shell ages — everything.

        I guess time will tell who is right.

      • Paul Milenkovic,

        The organic as well as inorganic carbon fluxes are roughly known, as inorganic exchanges don’t use or release oxygen and have little (parallel) influence on δ13C levels, while the biosphere exchanges also exchanges oxygen and has a huge (opposite) influence on δ13C levels. That makes that the seasonal to multi-millennia exchanges are more or less known:

        Continuous between equatorial upwelling zones and polar sink zone via the deep oceans:
        ~40 GtC/year, hardly influenced by temperature or CO2 pressure changes.
        Oceans are dominant and maintained (in the past) the equilibrium between pCO2 and δ13C in the ocean surface and the atmosphere.

        Seasonal:
        Oceans:
        Temperature up: CO2 up, δ13C slightly up
        ~50 GtC out and in\
        Biosphere:
        Temperature up: CO2 down, δ13C strongly up
        ~60 GtC in and out
        Vegetation is dominant.
        Little change from year by year temperature and long term CO2 changes.

        Year-by-year:
        Oceans:
        Temperature up: CO2 up, δ13C slightly up
        Biosphere:
        Temperature up: CO2 up, δ13C strongly down.
        Huge changes from temperature changes which level out to (below) zero in 1-3 years.
        ~8-10 GtC/°C (4-5 ppmv/°C) change on short term, vegetation dominant.
        Source: presentation by Pieter Tans at the festivities of 50 years Mauna Loa, from slide 11 on:
        http://esrl.noaa.gov/gmd/co2conference/pdfs/tans.pdf

        Multi-decades to multi-millennia (from ice cores and sediments):
        Temperature up: CO2 up and δ13C slightly up.
        Average 32 GtC/°C (16 ppmv/°C), (deep) oceans dominant.

        The problem with your theory (and a lot of others like Salby in the past), is that the huge correlation between the temperature and CO2 rate of changes is entirely from the noise: the year by year variability which is short living and has a negative influence on the trend, thus is not the cause of the increase.

        Remains human emissions – which are twice the measured increase in the atmosphere or the oceans.
        Over 3 million samples of ocean surface water were taken over time. Feely e.a. have compiled some 2 million of them into a map to show where the main ocean CO2 sinks and sources are. In area weighted average, the oceans are at 7 μatm less pCO2 than the atmosphere, that means that in average the oceans are more sink than source and can’t be the cause of the increase in the atmosphere.
        See: http://www.pmel.noaa.gov/pubs/outstand/feel2331/exchange.shtml and following pages

        Moreover, if temperature was the cause, the carbon content of the oceans would go down and the pH would increase, while we see the opposite. Here for Bermuda (FIg. 5):
        http://www.biogeosciences.net/9/2509/2012/bg-9-2509-2012.pdf
        All (six) longer term stations at different locations show the same trends.

        Compared to other periods in history, the current temperature is not extremely high: the MWP was probably as warm as today, the Roman period and several other periods were certainly warmer, but in all periods CO2 was not more than ~300 ppmv. The current increase of CO2 would be visible in all, even low resolution, ice cores up to 800,000 years ago, but it is not…

        Thus while mathematically one can fit the variability and trend by any mixture between temperature and emissions, temperature is the main cause of the variability while emissions are the main cause of the trend, which fits all observations…

  11. What a moron. Even elementary counting the ins and outs would show that gardens in average are more sink than source for CO2, as not every gram of CO2 captured is released again. Some of it will remain in the soils, roots, as humus, peat, and ultimately give browncoal and coal…
    If they even don’t know that all that garden CO2 was taken out of the atmosphere some months to years before, what kind of scientists are released on this world nowadays?

    • “what kind of scientists are released on this world nowadays”
      Well, he’s not quite released – it seems to be a PhD project (with co-authors). But yes, all the CO2 flux they are talking about is CO2 that was recently taken from the air, and is part of the ancient photosynthesis/respiration cycle. The abstract, journal Environmental Pollution, seems just as ignorant about this as the press release.

    • It’s not so simple. The process of fixation in the soils and respiration to the atmosphere is a transmission phenomenon, which will have an assortment of oscillatory modes and time constants, modulated by temperature, moisture, and nitrogen content.

      It’s not like every year, the plants transfer CO2 to the soil in the summer, and then the soil gives up all its CO2 in the winter. The soil, in fact, is a vast reservoir for CO2. Its respiration process can unfold over timelines of decades if not centuries.

      You always fixate on static accounting for systems which are highly dynamic in nature. The world is not so simple.

      • Well, we could do a bit of this analysis on my Wisconsin dairy farm. We till in crop residues every once in a while ( no till in between using glyphosate on the 2/3 contour rotations), and manure spread regularly on a contour several times per week. Amazing how well fed dairy cows pile up manure. Sort of like well fed climate scientists.
        Farm Objective is to keep soil carbon residue content as high as possible. Good for aerating earthworms, soil moisture retention, nitrogen fixing legume bacteria. Returns manure to Mom Nature. And such. This fellow is welcome to expand his Ph.D thesis to the big world where it really counts. But then, he might not graduate, since farmers have known this stuff for a very long time. Affects crop yields.

      • Bart,

        The dynamics is not of much importance here, as all soil carbon was fixated out of the air in the previous months to maximum a few decades in most urban settings. The point is that the researchers added these natural CO2 releases to the “emissions”, while they shouldn’t have counted it at all.

        Worldwide, the diurnal change in CO2 is ~60 GtC (~30 ppmv CO2). ~60 GtC release from soils at night, about the same during the day and 120 GtC uptake during the day by photosynthesis, slightly more net uptake than release.

        The seasonal change is also about 60 GtC between spring-summer-fall and fall-winter-spring. The net uptake, thus what remains in the soils for longer periods is currently around 1 GtC/year.

        While the diurnal and seasonal changes are huge, the buildup of organics in soils is a rather slow process, except if enhanced by adding a lot of organics from other parts of the earth…

      • “The dynamics is not of much importance here…”

        I get that things you do not understand are rarely of much importance. You just make up a story to fill the gap.

      • Bart,

        All carbon forms in the soils of urban settings is quite recently taken out of the atmosphere, except if they have built the city on peat (like Amsterdam) or coal(/methane) near the surface, then all release of CO2 by soil bacteria is from carbon that was recently taken out of the same atmosphere where it is released now, only with a delay of a few months to a few decades.

        The dynamics are of zero interest here, even if in one year almost all new carbon in the soil is released and next year none… The simple result is that at maximum all the stored new carbon is released as CO2 again or that some of it remains in the soil as new peat or pre-coal. Net effect: zero emissions averaged over a few decades from that source to a (small) net sink. Never a net source. What the base of the above story was…

    • more sinks that sources yes, but gardeners often import organic material to dump on their gardens, be it bagged compost or food scraps. I read an interesting report form the US forestry department which stated that it took 20 cubic kilometers of air to provide enough CO2 to grow an acre of harvestable trees. Obviously this is a net air volume across the span of time to grow the trees, but it makes it clear that CO2 is hard for plants to gather due to its scarcity. It’s also bleedingly obvious that there’s not enough CO2 to go around! Some doubt the statement, but it’s not difficult to take the total mass of these trees trees and work out how much air is used in making them, given CO2 is at a concentration of 0.04% .. Once you wrap your head around these numbers it becomes clear CO2 levels are way too low.

      I studied botany and later worked as a landscaper. Where I live our ‘soil’ is largely sand and the dogma was to dig in compost to enrich the soil. Clay soils are different, digging in organics also helps break up the clay making it easier for plant roots to penetrate and air and water to get in and out. I got thinking about digging in organics and it occurred to me that by digging it down into the soil, whatever nutrients were being added were being wasted as they leached away from roots quicker than had the material simply been dumped on the surface. Tests later confirmed this..

      But the big revelation came when I stopped and thought about what compost was actually providing (I studied chemistry too) and theorized that aside from the nitrogen added by decaying microbes feeding on the organics, the bulk of the fertilization effects came from the CO2 released. 20kg of organics disappears pretty quickly to leave the same sterile white sand.. so I rigged some bottles to conduct a small experiment comparing seeds grown in: inorganic fertilizer enriched soil ; organic enriched soil and the third ; sterile soil with organics in a second bottle. Each growing bottle was attached via a tube to a second bottle to ensure the same volume of air. The inorganic fertilized seedlings grew fastest and failed early (I presumed CO2 deprivation) the second and third grew at essentially the same rate to the same size. I’d have loved to do this experiment more thoroughly and with a much larger sample size but health and $ prevent this.

      Nonetheless it was clear that decaying organics did not need to be *in* the soil, merely nearby – suggesting the gaseous CO2 was feeding the plants via the air – root contact was not needed.

      • Karl,

        Nice experiment you have done!
        Indeed “mulching”, adding compost or simply grass cuts or other rests from plants in between the growing crops makes that plants grow a lot better and also regulates soil moisture a lot better than bare ground for dry and wet days, especially for sandy grounds (which I have here too).

        That is one of the rules organic growers use and I have practiced for over 30 years in my own (small) vegetables garden. There is one point where organic growing is weak: they have no good solution to prevent molds and what was used (copper sulfate) is hardly “organic” and since a few years forbidden in organic growing. I have always used (mild) chemicals to prevent molds…

        Nowadays just planting a few pumpkins on the compost heap: grows as hell and suppresses weeds, a lot less work for me…

  12. Here in Toronto, the left-wing city council will not allow parking pads. I understand that much of this has to do with both drainage and parking issues, but perhaps those who want the pads can now counter with “but I’m helping fight global warming by covering up my front yard”.

    Or is this super-sciency stuff relatable to only BACK yards? Do side yards get a pass? What about growing pot, that’s pretty good for the earth, isn’t it? Doesn’t that balance things out? Where do I get a grant to answer all these questions?

  13. In 1992, the late Maurice Strong, a UN official, warmista supreme, and overall nefarious individual, told a UN conference: “It is clear that current lifestyles and consumption patterns of the affluent middle class, involving high meat intake, consumption of large amounts of frozen and convenience foods, use of fossil fuels, appliances, home and work place air conditioning, and suburban housing are not sustainable.”

    Forgive me for being suspicious but this study really seems to have a phantom, ghostlike, mentor behind it (“suburban housing … not sustainable”). And, Obama’s distaste for suburbia is also of a kind if not as well known. But, his under the radar (“I’ve got a pen; and I’ve got a phone”) utilization of HUD for attacks on it are even less so.

    Into the high density public housing we shall go.

  14. From looking at the apparatus with no other information given other than a picture, they are not accounting for the plants in the yard and garden that would be capturing CO2 and putting it into plant material that would be in the soil as roots or on top of the soil as leaves and stems. No conclusions as to the balance of CO2 can be derived from this study alone.

  15. As i have written before on WUWT, upland topsoil, in the presence of adequate
    moisture, owes it’s richness to the amount of natural gas which perks up through
    it. The gas is oxidized by microbes and the CO2 rises.

    In areas which would normally have rich soil, putting a city there concentrates
    the up flow of these gasses in the areas not covered by concrete and asphalt,
    causing the reading of CO2 to be higher than the surrounding reference countryside.

    The same phenomena can be seen surrounding land fills which are placed on
    gas proof barriers. The gas is up wells around the barriers, causing high gas
    readings immediately surrounding the landfill boundaries. This anomaly has
    wrongly been blamed on land fill gas leaking through the gas proof barrier.

    The barriers simply concentrates the gasses which would otherwise be about
    same levels as the surrounding countryside.

  16. Isn’t rich composts the stuff of jungles? Of nature? Cement bad, jungle good? Now it’s jungle bad??? Or is it jungle good, jungle emissions good, but human-in-jungle bad, human-emissions-in-jungle bad?

    So… is this hinting that it’s not back to a hunter/gatherer existence for us then? I thought they were trying to knock us back into the Stone Age. What DO they plan to do with us? Oh, I know… Dear me.

    It seems nothing we do or can do is counted as “natural”. We could live purely in and with nature (back to the land) and it would still be “human emissions” = bad. What does it take to get the human animal recognized as belonging here and worthy? Why are we allowing human-haters run the show?

    Rhetorical questions, yes, but we do need to see a massive shift in how we view ourselves. Those who tear down our self-esteem need to be booted out the door, manipulators and guilt-mongers with them. We need to take back control and it starts with self-esteem and pride in our existence, in our achievements, in our potential. We need positive people in control, not people who secretly want us gone from the face of the Earth.

  17. “Study: Urban backyards contribute almost as much CO2 as much as cars and buildings”

    Whoa! Too many “as much”-es.

  18. Essentially this is simply a war on life – all lifeforms. The consequences of life is CO2 and methane. The brain-dead warmists, if they had their way, would have to terminate all life on the planet – plant and animal. We already have examples, Mars and Venus, and Venus has massive amounts of CO2 in its’ atmosphere.

  19. Why don’t they just come out and demand that all humans just commit suicide. The earth would be so much more clean and pure should that ever happen. Well it will almost happen. That is commonly called Armageddon. But that will be a horrible thing, that unless God intervenes no flesh would be saved alive. But this seems to be what the enviros really want.

  20. Duh. I think I must emit more CO2 than anyone else in the street. I have a small rain forest that I keep watered in the back yard. I compost the lawn with grass clippings.
    If I believed the Global Warming models, I would have cut the lot down and concreted over the yard long ago. CO2 is part of the carbon cycle of life. To get rid of carbon pollution, all you have to do is bury every living organism growing, and sterilize the earth.

  21. So now we’re measuring “pollution” being emitted from your garden. Now I’ve seen it all. So long. And thanks for all the fish…..

  22. So – and where do they think the CO2 in that decaying mulch came from in the first place? Plants grow by absorbing CO2 from the atmosphere. When they die and decay they release it again. The net contribution from these processes is zero.

    This is like expressing concern that we might be making the atmosphere bigger because every time we breathe out we add gas to it. Over time all those humans breathing out will add enough gas to the atmosphere to turn the planet into another Venus, obviously this is a matter of concern worthy of further study supported by a research grant or two. You just have to contrive not to mention or somehow let anyone notice the blindingly obvious fact that we also breathe in.

  23. My data is about 15 years old, when atmospheric carbon (as CO2) was 730 gigatonnes (Gton) of carbon so present it as such (& all numbers cited are approximations). Soil humus is responsible for 60 Gtons carbon flux of which 50 Gtons goes via soil respiration into the air. The kind of soil microbiota which is short lived holds 130 Gtons of carbon & that biota which is long lived holds 700 Gtons; which under 2000 deforestation rate accounted for 3 Gtons of carbon flux into the air. I am going to resume that the article measurement of urban garden flux would be a combination of soil humus respiration & soil biota dynamics

    . Living plants on the planet (15 years ago) held 600 Gtons of carbon & dead plants on the planet held 200 Gtons of carbon; the plants (aside from microbes & humus of soil) flux back into the atmosphere 50 Gtons of carbon via all plant respiration. In counter flow plants move 100 Gtons of carbon into themselves via photosynthesis with a part of that total photosynthetic carbon also fluxing into ocean photo synthesizers

    With regard to forests we need to distinguish tree or tree stand age because trees “fix” carbon when grow but when mature they can flux out enough carbon so that they are no longer just a “sink” for carbon. A decade ago about 1/3 of the carbon in land plants was in standing forests but I suspect this may have changed with greening occurring in African scrub brush eco-systems.

  24. I don’t mulch, and at the rate the grass grows there is no doubt that my back yard is a net carbon sink..

    except when I mow. ;-)

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