More on Phytoplankton

On the heels of my last post about iron fertilization of the ocean, I found another interesting paper on the topic. This one, written by Long Cao and Ken Caldeira in 2010, was much less hopeful.

Instead of a small-scale field test, Cao and Caldeira decided to model iron fertilization using the ocean GCM from Lawrence Livermore National Laboratory. To account for uncertainties, they chose to calculate an upper bound on iron fertilization rather than a most likely scenario. That is, they maxed out phytoplankton growth until something else became the limiting factor – in this case, phosphates. On every single cell of the sea surface, the model phytoplankton were programmed to grow until phosphate concentrations were zero.

A 2008-2100 simulation implementing this method was forced with CO2 emissions data from the A2 scenario. An otherwise identical A2 simulation did not include the ocean fertilization, to act as a control. Geoengineering modelling is strange that way, because there are multiple definitions of “control run”: a non-geoengineered climate that is allowed to warm unabated, as well as preindustrial conditions (the usual definition in climate modelling).

Without any geoengineering, atmospheric CO2 reached 965 ppm by 2100. With the maximum amount of iron fertilization possible, these levels only fell to 833 ppm. The mitigation of ocean acidification was also quite modest: the sea surface pH in 2100 was 7.74 without geoengineering, and 7.80 with. Given the potential side effects of iron fertilization, is such a small improvement worth the trouble?

Unfortunately, the ocean acidification doesn’t end there. Although the problem was lessened somewhat at the surface, deeper layers in the ocean actually became more acidic. There was less CO2 being gradually mixed in from the atmosphere, but another source of dissolved carbon appeared: as the phytoplankton died and sank, they decomposed a little bit and released enough CO2 to cause a net decrease in pH compared to the control run.

In the diagram below, compare the first row (A2 control run) to the second (A2 with iron fertilization). The more red the contours are, the more acidic that layer of the ocean is with respect to preindustrial conditions. The third row contains data from another simulation in which emissions were allowed to increase just enough to offest sequestration by phytoplankton, leading to the same CO2 concentrations as the control run. The general pattern – iron fertilization reduces some acidity at the surface, but increases it at depth – is clear.

depth vs. latitude at 2100 (left); depth vs. time (right)

The more I read about geoengineering, the more I realize how poor the associated cost-benefit ratios might be. The oft-repeated assertion is true: the easiest way to prevent further climate change is, by a long shot, to simply reduce our emissions.


7 thoughts on “More on Phytoplankton

  1. Another case of GIGOSIM? I remember one time modeling the dynamic performance of a military HMMWV negotiating rough terrain as fast as it could safely go. The 3D model was very complex and the simulations were taking a long time to complete. My boss was anxious for the results, and I told him he would have to wait. He said, “Can’t you use a quarter model and get the results faster?” Like, yes, can’t you imagine a mono-HMMWV running around over rough terrain on a single wheel? Which quarter would give better results?

    So this simulation runs out 90 years into the future, and how many boundary conditions does it have? How many boundary conditions are gestimated and how many are ignored and how many are unknown? An experienced climatologist likely could have scratched out an educated guess on the back of an envelope just as accurate as those computations performed on massively parallel processors that require a secret clearance to access.

  2. Those aren’t acids if their pH is above 7.

    If the pH of a substance decreases, it’s becoming more acidic. It doesn’t matter where the pH is on the scale, only which direction it’s going. -Kate

    • Comparing ocean water with pure laboratory H2O is arbitrary. And “it cools down” after a hot summer’s day, no freezing needed or offered.

      BTW if you don’t want to look like a denialist, perhaps you should pick your talking points less stereotypedly. We have lists of them you know :-)


    Before acid rains, forests in Europe used to grow at about 1/4 meter per year. Then acid rains dropped that growth rate to 2-3 centimeters per year. Then in the early to middle eighties the trees began to die.

    So we propose to put more sulfer into the atmosphere to lower the temperature and kill all the trees that absorb CO2. Then after we have killed all the trees and exhausted the fossil fuels, the short persistence SOx acids will disappear, but the long persistence CO2 will not. So we will have moved on from fossil fuels to renewable energy, but it will be too late to save humanity from the disastrous consequences of 600 ppm CO2 and runaway rises in CH4. What do all those fancy models have to say about reduced SOx and huge releases of CH4 caused by rising temperatures associated with high levels of CO2?

    If CH4 killed dinosaurs, imagine what it would do to humans. Humans may be more intelligent than dinosaurs, but we are not more privileged.

    I think you are mixing up your extinctions – dinosaurs were wiped out due to an asteroid impact, not CH4. -Kate


    An asteroid impact is believed to have been responsible for initializing one mass instinction 65.5 Ma years ago. However, the impact itself was not responsible for much of the extinction; that was likely the result of climate change brought about by the astroid’s impact. If the astroid’s impact increased volcanic activity, then rising CO2 levels may have increased global temperatures that could have released more methane gas that may have further increased global temperatures.

    Some think that the skies were dark for years after the impact. But that could not have been entirely from debris thrown up by the astroid’s immediate impact, because gravitational forces would have eventually returned most of those particles back to the surface. However, continual volcanic activity as a result of the astroid’s impact could have provided a plentiful supply of particles for decades or centuries.

    There have been a number of mass extinctions, and only one is believed caused by an asteroid impact. A common cause in several mass extinctions is believed to have been global warming associated with high levels of CO2, and if massive levels of greenhouse gas CH4 might be associated with rising temperatures as the result of higher levels of CO2, then it could well be that CH4 was involved in some mass extinctions. Were the levels of methane gas high enough to cause asphyxiation? Probably not, but they certainly may have been high enough to cause further rises in global temperatures. There are many who believe that runaway methane gas associated with rising global temperatures is a real possibility. What do the models have to say about this?

    Consider the 993 ppm CO2 or the at-best 833 ppm CO2 scenarios discussed above. Are these levels not considered excessive according to our current excessive 394.5 ppm level? How much °C rise in global temperature is necessary before 50%, 60%, 70% of the current habitable land becomes too hot for year-round human survival? How much life will the future inhabitable polar regions be able to support? How much of that land will be arable, and will there be sufficient moisture to support a massive influx of humans, not to mention other migrating animals? And what about seasonal changes? While the warmer months may be tolerable, the colder months with little or no sunlight will be unbearable. Many humans and other animals will have to migrate away from the polar regions during the colder months. Where will they go, how will they get there, and how will they survive?

    If the human population is around ten Billion when climate disaster strikes, how many of those ten Billion will fit into the polar regions? Who will get to go, and what will happen to the rest? This is not the Titanic; there will be no lifeboats. Humans have forgotten how to survive without cheap oil, without food on the grocery shelves, without furnaces and airconditioners, without cars and busses. What happened to the great civilizations of the Ancient Southwest?

    Click to access sar_press_a_history_of_the_ancient_southwest_chapter_1.pdf

    Was it political or environmental? How could entire civilizations have disappeared in a few generations? Could it happen again, but on a much larger scale?

    Nature has taught animals to survive by protecting their offspring. Humans can safely be around most animals that don’t have offspring (unless you’re their prey), but these animals will attack to protect their young. Humans have that instinct too, but they have an ability beyond other animals, the ability to foresee the future not only for their immediate offspring, but for many generations to come. Humans not only have the ability to protect their immediate offspring, but to protect many generations of their offspring. But we are not doing it. We are not even protecting our immediate offspring. We are not doing anything to reduce the rate at which atmospheric CO2 increases. In fact, we are producing and consuming ever more amounts of oil, gas, and coal, even though we are well aware of the consequences of doing so. If all other of Nature’s animals knew what we know, they would immediately stop doing anything that put their offspring in danger. But we, the most intelligent animals on earth, think only of ourselves and nothing of our offspring. Perhaps some of us feel sorrow for the terrible lives we might imagine facing our offspring, and maybe some of us even worry about it, but we don’t do anything to change those prospects. Climatologists talk and talk and no one hears. Sacrifice is no longer in our vocabulary. Policymakers know what climatologists think is good for us, and they know what we think is good for us. And since there are many more of us than climatologists voting for them, policymakers will gladly ignore all common sense.

    There is an old saying, “When the going gets tough, the tough get going.” I think that is very true. Right now, the going is not tough and the tough are not going. Life is too good. All who could get tough are happy in their conditioned homes and cars and tractors, and all who can’t get tough can only shout into the wind or succumb to the elements. In “A History of the Ancient Southwest” the author states that in times of extreme duress there are some who prefer telling others how to survive. But in times of no duress, no one steps forward. So ancient civilizations may have evolved from times of duress, but they declined and vanished in times of no duress, because no one cared.

    Today? No one cares. No one is stepping forward. One might think that is stepping to the plate. But policymakers won’t be found there, only wishful thinkers, people shouting into the wind. Only when policymakers start feeling the real heat will they start stepping forward. And it will be far too late to save most of the human population from a painful demise.

    Click to access WorldPop2300final.pdf

    “On this score, calamities of nature come first to mind. The kind of celestial collisions that extinguished the dinosaurs and could well do the same to humans occur so rarely—apparently there were three such instances in the last 300 million years—that they perhaps would not deserve even a footnote in an exercise presenting 300-year projections. But, given its documented past frequency and severity, the possibility of abrupt climate change certainly would rate a mention in speculating about population trends over three centuries. The major concern here is not gradual global warming, to which modern industrial societies could adjust at a tolerable cost, and from which even net benefits for world agriculture might ensue, but possible major temperature drops, such as occurred some 12,000 and 8,000 years ago, lasting many decades or even centuries. These occurred without the involvement of human agency. In the future they might, additionally, be triggered by human-induced global warming affecting oceanic currents and causing a chain reaction of adverse weather changes. This could lead to a major reduction in carrying capacity through diminished food production, water shortages, disruption of energy supplies, global conflicts in competition for scarce resources, and ultimately to massive population loss. This last possibility, with or without climate change, may also be the consequence of unforeseen worsening of the epidemiological environment—causing peaks analogous to those associated with the Black Death, the Spanish influenza epidemic, and HIV/AIDS, but writ even larger.”

    It is unlikely that writers of WorldPop2300final.pdf understand the real dangers and consequences of runaway greenhouse gasses. Who would, considering no one today has experienced such climatic effects? And little mention of diminishing water resources is made. Much of human food consumption today comes from irrigated croplands fed by snowpack-fed mountain streams and aquifers, many of them drying up. As the world pumps out their sources to support its burgeoning population, natural lakes and springs are drying up at alarming rates.

  5. This is a very interesting look at the pros and cons of ocean fertilization. Thank you.
    I wonder, do you have any information about how such geo engineering would affect food webs in the oceans? And what about oxygen content?

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