This column is moderated byĀ BĆ©la LiptĆ”k, automation and safety consultant and editor of the Instrument and Automation Engineers' Handbook (IAEH). If you have an automation-related question for this column, write toĀ [email protected].Ā
Z. Friedmann
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A: You hit upon a large subject, one that will take up a full chapter in my upcoming book to be published by ISA. I will try to give you a brief answer.
Figure 1: The average surface temperature of the world's oceans, using the baseline of 1971 to 2000 average. The shaded band shows the range of uncertainty in the data based on the number of measurements collected and the precision of the measurements used. Source: EPA.Ā
Figure 1 shows the rise of the surface temperature of the oceans during the industrial age. Now, if we look at the protection against climate change as a "control loop," the measurement of that loop is that temperature, which has increased by only about 1.5 °C during the past century, and today we're just beginning to see its consequences (melting ice, wildfires, hurricanes). This rate of rise is still slow (2.0-3.0 °C per century) but is accelerating. My estimate is it will reach a rise of about 5.0 °C by 2075. In my view, we'll never stopat 2.0°C (recommended by the Paris Agreement of 2015) and particularly not at 1.5 °C (recommended by the U.N. Intergovernmental Panel on Climate Change ā IPCC in 2018) because this high-inertia process is totally out of control.Some believe that because the numbers describingĀ the temperature rise are small, the problemĀ we face is also small. This is not the case. LetĀ me compare them with our own body temperature,Ā which is accurately controlled by our brain.Ā The body temperature of a healthy, resting adultĀ human being is 98.6 °F (37.0 °C). Our "thermostat"Ā (called the hypothalamus, a portion of theĀ brain) controls body temperature. The span ofĀ our thermostat is 36.4ā37.1 °C (97.5ā98.8 °F) orĀ about 0.7 °C. This thermostat turns on shiveringĀ at 97.5 °F and initiates sweating at 98.8 °F. I mentionĀ this only to illustrate that certain processesĀ must be controlled within small limits becauseĀ small temperature changes can have large effects.
According to all scientific data, theĀ thermostat of global temperature control is CO2Ā concentration in the atmosphere. If it rises, theĀ global temperature rises (because the thermalĀ insulation of the planet increases), and when itĀ drops, the planet cools.
During the past 1 million years, nature "controlled"Ā this concentration by keeping the inflowĀ of CO2 into the atmosphere (generated by animalĀ life and man) roughly equal the outflow (intake ofĀ plants and dissipation by the oceans), and thereforeĀ the atmospheric concentration of CO2 stayedĀ roughly constant, never exceeding 280 ppm evenĀ during ice ages, changing sun spot numbers, volcanicĀ activity or meteor impacts.
If we look at the atmosphere as a tank and CO2 concentration as the level in that tank, then we could say that this level stayed reasonably constant for a million years because it never exceeded 280 ppm (the planet didn't need to start "sweating") as nature took care of it. Since the beginning of the industrial revolution, humans gradually took over this control from nature, CO2 concentration in the atmosphere increased from 280 to more than 410 ppm, and it's predicted by most models that it will reach or even exceed 500 ppm by the end of this century.
If a control engineer was to bring this process under control by returning CO2 concentration to the stable, pre-industrial state, the task would be to balance the in and outflows of this tank, and on top of that, remove roughly half of the CO2 that accumulated during the industrial age. If a conventional level controller was installed on this tank, it would see an error of 410 ā 280 = 130 ppm and a past error accumulation of some 400-500 Gt (gigatons) of carbon. It would immediatelyĀ close the inlet valve and open theĀ outlet valve.
Unfortunately, in this process, theseĀ valves are stuck. The outflow from theĀ tank (the CO2 intake of the plants andĀ dissipation by the oceans) canāt beĀ increased. In fact, it has probably decreasedĀ during the past century becauseĀ of deforestation, acidification of theĀ oceans, and building of dams/reservoirs,Ā holding 8,000 km3 of water, which alsoĀ emit carbon to the atmosphere. In short,Ā this outlet valve is almost completelyĀ stuck, and we have no technology to openĀ it further except reforestation, which isĀ unlikely due to overpopulation (during theĀ industrial age, population increased fromĀ 1.0 to 9.0 billion).
Figure 2: This figure shows the fast carbon cycle (left - on land, right - in the oceans) in billions of tons of carbon per year. Yellow numbers are natural fluxes; red are human contributions. White numbers refer to stored carbon. Source: NASA.Ā
As shown in Figure 2, every year we send 9 Gt of carbon into the atmosphere. 3 Gt of that is taken up by the photosynthesisĀ of plants, 2 Gt is dissipated by theĀ oceans, and 4 Gt remains in the atmosphereĀ for the next 20 to 200 years. So,Ā the inflow exceeds the outflow by 4 Gt/yr.
We do have some means to reduceĀ this inflow, such as using more bicycles,Ā public transport, converting to electricĀ cars, insulating our homes, using smartĀ thermostats and appliances, eliminatingĀ animal products from our diet (whichĀ cuts greenhouse emissions by moreĀ than 10%), introducing carbon taxes (notĀ cap-and-trade, but taxes), and eventually,Ā fully converting the energy economyĀ from fossil/nuclear fuels to carbon-freeĀ ones. The speed of conversion is a functionĀ of both the marketplace and governmentĀ support. Where both are present,Ā the conversion is faster (in CaliforniaĀ today, green electricity is 30% of the total),Ā while where only the marketplace isĀ driving the conversion, it is much slowerĀ (15% in the U.S. overall).
It will probably take a generation orĀ two to overcome the resistance of theĀ fossil industry. Leaving some $35 trillionĀ worth of fossil fuel in the ground justifiesĀ some resistance, and it will take time forĀ society as a whole to realize that we mustĀ convert to solar energy and use hydrogenĀ as the means of storing, transporting andĀ distributing this energy to areas whereĀ insolation is insufficient. (For more solarĀ storage technology, see my book, PostĀ Oil Energy Economy, or tune in to the video).
What even the best of our leaders seemĀ to not understand is that, even after we'veĀ balanced the in and outflows, we will notĀ have returned the planet to pre-industrialĀ conditions because even after this tremendousĀ technological and political transformationĀ effort, we didnāt even start toĀ remove the already accumulated 400-500Ā Gt of carbon from the atmosphere, whichĀ can stay there for 20-200 years. And, asĀ long as that accumulation remains, the CO2Ā concentration does not drop and the planetĀ will keep warming.
This is obvious to a process control engineer, but not to our well-intentioned leaders who wrote the Paris Agreement in 2015 or the smarter U.N. experts who participated in the IPCC meeting in 2018. It is for this reason that we who understand process control have the responsibility to explain that the present uncontrolled rate of carbon accumulation will reach approximately 500 ppm by the end of this century, at which point the tropical regions of the planet are likely to become unlivable, and the resulting biblical-scale migration could destroy human civilization.
BƩla LiptƔk
[email protected]

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