Simplest climate model yet – a bathtub

Climate change: How could artificial photosynthesis contribute to limiting global warming?

Scientists calculate areas needed for forestation and artificial photosynthesis

The atmosphere can be compared to a bathtub that can only be filled to its rim if global warming is to be limited to a certain level. We could create another small outward flow with negative emissions. However, there is no way around turning off the tap. CREDIT M. May/HZB

After several years during which global emissions at least stagnated, they rose again somewhat in 2017 and 2018. Germany has also clearly missed its climate targets. In order to keep global warming below 2 degrees Celsius, only about 1100 gigatonnes of CO2 may be released into the atmosphere by 2050[1]. And In order to limit global warming to 1.5 degrees, only just under 400 gigatonnes of CO2 may be emitted worldwide. By 2050, emissions will have to fall to zero even. Currently, however, 42 gigatonnes of CO2 are added every year.

Almost all the various scenarios require “negative emissions”

The Intergovernmental Panel on Climate Change (IPCC) has numerically simulated various scenarios. Only in the most optimistic scenario can the climate target still be achieved by means of immediate and drastic measures in all sectors (transport, agriculture, construction, energy, etc.). In the less optimistic scenarios, the global community will have to take additional measures beginning in 2030 or by 2050 at the latest: we will have to implement “negative emissions” by removing large quantities of CO2 from the atmosphere and store them permanently in order to balance the carbon budget. One example of negative emissions is large-scale forestation – forests bind CO2 in wood as long as it is not later used as fuel. But CO2 could also be removed from the atmosphere and bound using artificial photosynthesis.

Physicists have now calculated how this might work. Dr. Matthias May of the HZB Institute for Solar Fuels is an expert in artificial photosynthesis. Dr. Kira Rehfeld is an environmental physicist at the University of Heidelberg studying climate and environmental variability.

Natural photosynthesis: a surface area the size of Europe would have to be forested

In a median scenario, at least 10 gigatonnes of CO2 per year would have to be removed from the atmosphere beginning around 2050 to balance the climate carbon budget. Forestation and cultivation of biomass for reducing CO2 compete for the same areas as are needed for agriculture, however. With just more biomass alone, it is therefore difficult to reach this scale, for natural photosynthesis is not a particularly efficient process. Leaves are able to use a maximum of two per cent of the light for converting CO2 and water into new chemical compounds. The two physicists argue that in order to bind 10 gigatonnes of CO2 per year in the forest, about 10 million square kilometres of the fertile areas on Earth would have to be planted with new forest. This corresponds to the area of continental Europe (up to the Urals!).

With artificial photosynthesis, an area the size of the State of Brandenburg could suffice

Materials systems currently being researched for artificial photosynthesis might bind CO2 with considerably greater efficiency. Already today, on a lab scale, photo-electrochemical systems made of semiconductor materials and oxides can utilise about nineteen per cent of the light to split water, for example, and thus realize part of the photosynthesis process. However, the material system envisaged by May and Rehfeld is not about producing hydrogen with sunlight, but instead about binding CO2 molecules and converting them into stable chemical compounds. „However, this is a relatively similar problem from the point of view of physical chemistry”, says May.

The prerequisite, however, is that it will be possible to develop by 2050 large-scale, durable modules that use solar energy to convert atmospheric CO2 into other compounds. The required area for this solution can be calculated. Assuming efficiency of nineteen per cent and fifty per cent system losses, around 30,000 square-kilometres of modules could be sufficient to extract 10 gigatonnes of CO2 from the atmosphere annually. This corresponds to the approximate area of the German federal State of Brandenburg.

“These kinds of modules could be placed in non-agricultural regions – in deserts, for example. In contrast to plants, they require hardly any water to operate, and their efficiency does not suffer when exposed to intense solar radiation,” explains May. The extracted CO2 could be converted to formic acid, alcohol or oxalate and combined with other compounds (such as calcium chloride) to form solid minerals that can be stored or even used in the form of plastic as a building material.

Focus on development, not on miracles

Even if May and Rehfeld are convinced that such solutions should be considered more closely, they warn against relying on technical miracles. This is because such systems still only function at the smallest scale, are expensive, and not stable in the long term. Changing this requires large investments in research and development.

“It might be possible to develop such modules, but even if we could then build them, we estimate that the conversion will cost at least 65 euros per tonne of CO2. The extraction of 10 gigatonnes of CO2 thus results in costs of 650 billion euros each year. Moreover, negative emissions can only be the last resort to slow dramatic climate developments. The best thing now would be to drastically reduce emissions immediately – that would be safer and much cheaper”, says May.


HT/David B

From EurekAlert!

Public Release: 16-Jan-2019


83 thoughts on “Simplest climate model yet – a bathtub

  1. Ok, let Germany pay for it and install it in Brandenburg. I instead will sip some California Chardonnay
    while listening to the Brandenburg Concerti.

  2. Better yet, find a way to produce transportation fuel by artificial photosynthesis at reasonable cost.

    • Will Biofuels suffice? Not as reasonable as petroleum though.
      I wonder if you could operate a farm using only harvested fuel stock from the farm? I suppose it would help to have the fuel refinery next to the farm.

      • Flatulence-propelled draft horses and bullocks after they are fed with baked beans! Seemples!

    • I’m replying to my own comment to re-direct attention at what is claimed in the article, that “photo-electrochemical systems made of semiconductor materials and oxides” could synthesize carbon compounds from atmospheric CO2. In one’s dreams, for example, a semiconductor-based solar module producing and storing methane or methanol from atmospheric CO2 and water vapor, would be far better than making intermittent electricity, and far better than sequestering the carbon into minerals.

      In other words, the fixation on removing CO2 from the atmosphere is misplaced already. But if effort is going into developing photo-electrochemical systems to process atmospheric CO2 into something else, make it into something really useful. Fuel.

  3. Good grief.

    Someone said to a scientist “You really need to explain things to the non-scientists in a simple way”.

    And this is the best he came up with.

    Seriously insulting. I can read, I don’t need Janet and John cartoons!

    • You know at a quick glance that a scientist is being disingenuous when he goes out his way to use the word “carbon”(6 letters) instead of “CO2” (3 letters) in what is intended to be a simple model for non-scientists.

  4. Word counts:
    Total 833
    could 8
    might 3
    may 2
    if 4

    Artificial photosynthesis is what, sequestration or geoengineering? Both of those are in tight competition for the the dumbest idea of the last 30 years.

  5. A chemical plant covering 30,000sq km will cost trillions, no back of envelope needed! It would have to produce a useful product and not simply be a massive cisrly eyesore. With the “Great Greening^тм” having already expanded global forest cover by more than 15% (14% by 2014) and general “leafing out” cover of the planet by 18%, it looks to me like the Malthusians want to get out in front of Nature’s parade because this is already proving to give the benefits of carbon the lions share. Leave everything as it is and we will have a “Garden of Eden Earth”by 2050.

    • 650 Billion Euro’s per year? Heck, for a mere 325 B/year I’ll build desalinization plants and irrigate the Sahara and grow trees. I figure after about 20-30 years I’ll be able to supply a large part of the worlds lumber. Well not me, I’ll be dead.

  6. More fantasies from the delusional.

    “With artificial photosynthesis, an area the size of the State of Brandenburg could suffice

    Materials systems currently being researched for artificial photosynthesis might bind CO2 with considerably greater efficiency.

    Already today, on a lab scale, photo-electrochemical systems made of semiconductor materials and oxides can utilise about nineteen per cent of the light to split water, for example, and thus realize part of the photosynthesis process.”

    It is a classic “Popular Mechanics” fantasy about the future.
    A) Not invented.
    B) Portions that are invented are untested.

    Enter the science fiction writer to turn it into a false claim via press release.

    1) Plants utilize 2% of the sunlight for photosynthesis.
    2) The untested partial process uses 19% of sunlight to decompose water.

    Instead of their process requiring less land than their imaginary carbon dioxide capturing forest it will require far more land and return less than the forest.

    “photo-electrochemical systems made of semiconductor materials and oxides”

    N.B. They are careful to avoid specifying the exact components. Which allows them to skip defending toxic wastes and all of the smelting/refining/producing requiring copious fossil fuels.

    Alarmists and their pictogram comic book fantasies. Someone kept their head under water far too long.

  7. That graphical description is absolute bogus BS. Whoever made it must know it.
    Complete BS because it depicts as the **ONLY** input to bathtub as “Human Greenhouse Gass emission rate.”

    The natural CO2 sources of the oceans, the non-biologic land (acidic rain on calcium carbonate rocks), volcanoes/rift outgassing/deep ocean smokers, and the vast bioligc sources such as the tropics all have probably a 2 orders of magnitude greater emission rate than human’s fossil fuel burning and Portland cement cooking.

    That graphic would be close to accurate if it showed 10 firehouses shooting into the bathtub, representing natural sources, with a huge sucking pump on the bottom pulling that out.

    The key to understanding why this is so, that the annual MLO annual increase record only shows a weak coupling to estimated annual anthropogenic CO2 emissions. The MLO record shows a much greater reaction to the ENSO cycles and (of course) to the NH’s biological productivity in the late spring & summer months.

    And as to the text itself. It is utter garbage witchcraft-religion nonsense to believe, “In order to keep global warming below 2 degrees Celsius, only about 1100 gigatonnes of CO2 may be released into the atmosphere by 2050[1].”

    Only the true believers in the Church of CAGW actually believe in such a fine control of Earth’s climate and the CO2 control knob nonsense with all the massive uncertainties and hand-tuning puppetry in the garbage cargo-cult climate models.

    • The human contributions to atmospheric CO2 could be represented with a garden hose while natural processes are represented by fire hoses.

      Here’s a link to an IPCC graphic showing the CO2 budget. Note the precision of the numbers.

      On August 3, 2012, Brian H posted this quote:

      Cardellini et al’s 2011 empirical work on measuring the co2 emission from old lava fields in central Italy at 9 Giga-tons a year is a case in point. This calls into question the assumption that humans are responsible for all the increase in airborne co2 since the 50?s, which is based on theoretical calculations which put the global emission of co2 from volcanic sources at 0.138 giga-tons a year – nearly 100 times less than a small part of Italy. link

      As Brian noted, “Them’s some error bars!!”

      The precision with which the IPCC et al calculate the CO2 budget is simply not credible. It isn’t supported by measured data. Human emissions are less than the actual errors in the estimates of the other fluxes.

    • I like the bathtub model.
      Plants have been burying CO2 into the ground for the last 500 000 000 years. In that time the estimated amount in the air dropped from 0.7% to 0.0%. Plate tectonics is not fast enough to maintain a healthy balance.
      Only for the last 50-250 years have humans been hard at work to save all life on the planet, by digging up some of it.

  8. “And In order to limit global warming to 1.5 degrees, only just under 400 gigatonnes of CO2 may be emitted worldwide. ”
    Limit global warming to 1.5°? 1.5° over what exactly?
    Can somebody show me the formula that equates gigatonnes to degrees, particularly that equates 400 gigatonnes to 1.5°? What part of these 1.5° would be eliminated/removed/annihilated if those 400 GT were not emitted?

    • They still haven’t produced a shred of evidence that anything bad is going to happen if the Earth warms up by more than this magical 1.5C number.

      The original claim was that getting warmer than the Medieval Warm Period was uncharted territory, and somehow uncharted became “here be demons”.
      PS: The claim that warmer than the MWP is uncharted territory is also total BS, because in the last 5000 years, the earth has been warmer than the MWP 3 times. In the last 10K years, the earth has been as much as 2 to 3C warmer than the MWP for about 80% of the time.

  9. A leading scientist told me that if you study the history of scientific discoveries you will notice that research that produces the most beneficial results is often the least glamorous research. This is bad news for those who think that if they throw billions at glamorous research – including many involved with climate research – that they will come up with many breakthroughs.

    • The guy who finally cracked the blue light LED puzzle worked for a small company in a low budget lab.
      After the big guys had spent decades and 10’s if not 100’s of millions of dollars on that problem.

  10. I haven’t read this yet but when I saw that diagram at the top I just wondered whether it was me or someone else who had just flipped a lid?! Ye gods!

  11. “about binding CO2 molecules and converting them into stable chemical compounds”
    Such as coal, peat, oil, natural gas?

    …by using light…
    If they were really serious, they would use nuclear power to do it, and also use nuclear power to replace some usages of the CO2 producing stuff.

    The real clue here is that they are starting to realize that their climate target can not be achieved. Period.

  12. I have a bone to pick with the Green people. The DRAX power station in Great Britain is burning trees cut down in Louisana USA and shipping them around Florida to be burned and the greenies claim that is good. Trees, when burned, produce almost as much CO2 emissions as coal. If they were still burning coal, they could license the ZECCOM™¹ (Zero Emissions Coal Combustion) Process from us, and emit no CO2 emissions ever again. We also have the ZENGCOM™¹ Process that does the same for natural gas power plants. These two processes can reduce the 42 GT of C02 emissions by 76.1% to only 10.0 GT. How do we do it? Very simple, we burn the fuel in a pressurized combustor, that costs less than an atmospheric combustor, and release the flue gas underground into a sequestration facility. It will take the greeenies many years to get to that level. We can do it in far lkess than that. That makes abiug hoile in your bathtub analogy.

    • It’s worse than you say – the emissions resulting from the harvesting, processing and transport of the biomass from the US to Drax alone is, I recall, about 50% of the emissions from burning coal to produce the same amount of energy. This was from a government produced calculator published by the DECC.
      By the way, I think the forest being felled is in Carolina, but I may be wrong.
      Your process looks very interesting.

    • And how many of your plants exist?
      It would be interesting to know how you keep exhaust gasses underground and out of ground water, among many questions…

  13. Google biogeochemical carbon cycle.
    CO2 flows through the atmosphere like a river. The atmosphere is not a “tub”
    CO2 never accumulates in the atmosphere, from any source, natural or anthropogenic.
    The natural source fluxes and sinks are at least 25 to 40 times larger than anthropogenic.
    Adding 4 percent to the flow of a river, with a marker dye to distinguish the new flow from the original flow.
    The percentage of dyed water will never exceed 4 percent as it flows downstream to the infinite sink.
    The amount of anthropogenic CO2 in the atmosphere is therefore about 4 percent of the total.
    .04 times 400 ppm is 16 ppm.
    The remaining increase of CO2 above fossil fuel burning in the last century is due to destruction of tropical forests and farming, which have damaged the natural biogeochemical cycle. Shifting ocean currents are impossible to exclude, along with eutrophication on a global scale.

  14. Another example of how supposed science and discovering have degraded…

    One of the many fundamental mistakes of climate change and the blaming of CO2 is suggesting that 280ppmv is end all be all of atomspheric concentration. I find it telling that these organizations never talk about the actual temperature, concentration of CO2 in the oceans, water vapor concentration, etc or how these vary widely and wildly during a 24-hour period. Each measurement is a snapshot of that moment in time and each of those moments in time need to be heavily quantified and qualified. They always reports these numbers as scalars and rarely as rates or vectors.

    The “climate science” studies should have to follow the same GMP rules the FDA makes Pharmceutical companies follow.

  15. The bathtub idea was proposed at least 40 years ago as a substitute for the greenhouse analogy. i know because I ran a graduate seminar about the idea at that time. We rejected it in the seminar, as did most other people working on climate at the time, for many of the reasons presented by commenters here. At that time a much better approach appeared proposed by the then Soviet climatologist Mikhail Budyko (1920-2001). He proposed an energy budget approach that was a basic but more scientific approach.

    As I recall much of this early Soviet climate science and other science appeared through a translation agency set up by scientists finally allowed out of the soviet union.

  16. Should not the diagram reflect the natural and athropogenic sources and sinks of CO2 in their right proportions? Natural sources are missing entirely. Should be about thirty drops coming in and going out from mother nature and a single drip from us humans if one can believe the various carbon cycle accountings.

    We should not lie to the children.

  17. 10 giga tons for 650 billion per year?

    And how much adaption to this warming can we buy with 650 billion? IF there is anything to adapt to!

    Calling these people dipshits, is an insult to dipshits.

  18. If the IPCC prediction that 2 deg-C warming since late 1800s is very bad (not that I think it would be), and to the extent that warming over the next few decades as predicted by the IPCC is correct, 2C is unlikely to be avoided. For example, by the IPCC RCP scenarios (Representative Concentration Pathways for future CO2), an RCP of 8.5 reaches 2C about 2040 and RCPs 6.0 & 4.5 reach 2C by about 2060. The lowest RCP (2.5) does not reach 2C, but requires a major decrease in CO2 emissions within a few years, which is clearly not going to occur.

  19. It appears the message is: Burning fossil fuels is the same as peeing in the bath tub.
    And so now we need to let it drip out onto the floor.

  20. The bathtub us too simple. It does not reflect natural feedbacks to increasing temperature, which deserve their own input spigot. For whatever reason the planet is currently warming, a warming ocean will sink a bit less, and warming soils will add a lot more to the atmosphere.

    The surface tension of the ocean surface filters (fractionates) isotopes both in and out, with heavier isotopes being rejected both ways, but more stringently on outgassing. Ocean total flux is enormous, approaching 100Gt moving annually both ways, but since outgassing fractionation is 5x more stringent, ocean flux still nets light Carbon to the atmosphere at about -8 PDB. This -8 happens to be the current atmospheric ratio.

    Soils are essentially a one way carbon input to the atmosphere, just like humans. Soils kick in 60Gt annually; humans 10. Soils -21 PDB to the atmosphere; humans -24. Soil respiration increase with temperature is pretty linear and amounts to about a 5% increase per degree C. The reputed 1 degree warming is thus good for 3 extra Gt annually from soils.

      • This is the confusion. Does your biosphere include humans? Of course the Carbon based biosphere on a Carbon starved planet is a net sink for both mineral and biological Carbon. This is trivial. If the question is framed, “where does the atmospheric Carbon come from?”; simply stating that the biosphere is a net sink is not helpful. We are talking about the atmosphere, not the biosphere.

        Human cumbustion and soil respiration are unusual in being essentially one way additions to the atmosphere with very similar isotopic ratios. They are both biological in my world. Volcanoes are a mineral source with vaiable isotopic ratios. Weathering is a mineral sink subject to chemical fractionation and will leave heavier 13C in the atmosphere.

        I am certainly not quoting any mantra about permafrost.

        • Gordon,

          Have you prepared a Keeling plot (δ13C vs 1/CO2) or a 13C-CO2 balance calculation? Without any data analysis, it is not possible to evaluate your position.

    • “Soils -21 PDB to the atmosphere; humans -24.”

      And yet the observed decline in atmospheric 13C/12C tells us that on average the δ13C content of the incremental atmospheric CO2 is -13 per mil (PDB). Do you agree? Have you prepared a Keeling plot (δ13C vs 1/CO2) or a 13C-CO2 balance calculation? If so, please share.

    • “Soils are essentially a one way carbon input to the atmosphere”

      In that case how come there is such a lot of carbon in the soil? Modern-type soils have existed since the Devonian. They should have lost all carbn long, long ago.

  21. Global oligarchy and massive money transfers from the poor to this ruling class is the only solution they accept.

    CO2 cycle of the climate system sets to a new balance all the time taking into account all changes in sources and sinks. Satellites tell that sources are rain-forests and China.

    More vegetation and less concrete is fine for me.

  22. Besides being piss yellow, the tub is simplified to deceptive levels.
    And the cure offered is yet more climate fiction posed as science.
    Another boring, unoriginal, derivative, deceptive climate paper.

  23. OK- extract C & O from the air and turn it into organic chemicals without using h2o. Good idea.
    a) If not from h20, where’s the H come from?
    2] Whatcha gunna do wit da end products?

  24. Maybe they could, using the same bathtub pic, explain the mechanism that, to warm the water in your bath, you should warm the air in your bathroom. After all, THAT is what the AGW-crowd believes.

  25. The bathtub model could prb’ly do at least as good as the current “models”, and save a bundle of money and time. In keeping w/the modeller-PCism, use a range of different bathtub designs (a different one for each participating country so nobody feels left out) and then average the results.

    Then hope there isn’t a leftover “ring-around-the-bathtub”.

  26. “These kinds of modules could be placed in non-agricultural regions – in deserts, for example. In contrast to plants, they require hardly any water to operate, and their efficiency does not suffer when exposed to intense solar radiation,” explains May.

    Another stupid conjecture from Mr May Maybe. Photosynthesis requires six mols of water and carbondioxide each to get one mol of sugar.

    In deserts water as humidity is scarier than CO2. Of course logic is much more scarier in these folks.

  27. Even simpler is a concreter’s pan filed with water & lying in the sun which I saw in NYC 40 years ago. The dirty water welled up & down in short time intervals, and that told you all you needed to know about El Ninos and La Ninas.

  28. We have probably all seen some big ideas on either ameliorating the effects of “carbon” emissions or for pulling C02 from the atmosphere. These ideas go nowhere because the actual intent of those propagating “climate change” propaganda are not interested any stopping any alleged global warming. They want humanity to stop using fossil fuels altogether and to create a world government. They want to replace capitalism and freedom with socialism and serfdom.

  29. An important point in the diagram is that the sources are at different locations to the sinks. In a Berne model where CO2 is “well mixed” then this makes no difference. But it is clearly wrong. A kilogram of fossil fuels burnt in the summer Sahara dessert, or an equatorial rain forest, or a winter storm in the Antarctic oceans will have very different fate.

    The question is, “How wrong is it?”

    A follow-up paper to the last Levine paper (in 2013 I think), should tell us lot, but seems overdue. I can’t find any published data yet. At about that time, the simple approximate first-order decline in excess 14C from the bomb-spike (as measured at Jungfraujoch and Schauinsland) was approaching zero (I refer to the chemical equilibration, not a decline due to radio-active 14C decay).

    That was thus the time when the consensus thinking indicates 14C would have fallen back to the levels observed before human bomb-tests in the atmosphere produced a spike in 14C levels, and Levine’s paper showed that. But subsequently, the annual addition of ~3% of “cold” CO2 from fossil fuel sources should produce a commensurate decline in the levels of atmospheric 14C below the levels observed before human intervention. That is, unless the increase in atmospheric CO2 came from non-fossil fuel sources such as deforestation, other land use changes, or ocean degassing) which contain ambient levels 14C, thus producing little change in atmospheric 14C ratios.

    This should be a wonderful piece of data to show that the Berne model has either passed a significant test, or that it is holed below the waterline. Most likely, I would bet that it shows something in between. That is the way the data tends to go in the real universe. But the longer I don’t see this data being published, the more my suspicions will grow. If any one has that data, I would love to see it.

  30. I recently read an article that concludes worldwide greenery has increased 14% due to the increase CO2 in atmosphere. That surely makes sense to me as a Chemical Engineer, and also as the product of a farm where we saw huge increases in wheat and corn yields, coincidentally(?) as CO2 increased. Surely makes sense to me, when you increase reactant concentrations, yields go up. Why is this fact-of-life routinely ignored by “climate scientists”?

  31. Genetically engineered plant life will more efficiently absorb CO2 in the near future. Decreasing CO2 levels, starving plant life and endangering the planet, will be the next crisis for idiot globalists.

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