Can we resolve the climate debate?

Nov. 30, 2017
Part 1: Is global warming significant? Is it caused by CO2?

Resolve is probably too strong a word, but we can certainly analyze the climate change process the same way process control professionals evaluate any process before attempting to control it, because we know that in order to control a process, one must understand it! So the goal of this article is to prove whether climate change is a "Chinese hoax" or is in fact occurring; has parameters like gain, inertia, time constants, capacity and dynamics that can be determined; and determine the size and the speed of change of this variable, both if it's is left uncontrolled and when it is controlled. This knowledge is important because it tells us how much total change is needed and the time frame in it must be achieved.

Is present global warming significant?

For the past million years, the incoming and outgoing energies of our planet were in balance, and as a consequence, the average temperature of the earth's surface stayed at 15 °C. At the same time, the surface temperature of the moon, which receives the same amount of solar energy (340 W/m2) as we do, stayed at -18 °C. The earth was 33 °C warmer than the moon because it has an atmosphere, while the moon does not.

For the past million years, the earth's atmosphere contained a fairly constant amount of "naturally present" greenhouse gases, which acted like a mirror, reflecting more than half of the infrared energy that the earth radiated to the cold space that surrounds it, while the moon radiated all the energy it received back into space.

Our global energy imbalance started at the beginning of the Industrial Revolution in 1880, when global record-keeping began and when the greenhouse gas concentration of our atmosphere started to increase. At that time, the rate of temperature rise was less than 0.01 °C per decade. By today, this rate has increased to about 0.12 °C per decade, and the average global temperature has reached 16.1 °C. This is 1.1°C (2.0 °F) above the average in 1880, and for this reason, in April 2016, 195 nations signed the Paris Agreement, which sets a maximum allowable limit for this warming to 2 °C (preferably 1.5 °C). Most scientists believe that if this process is allowed to remain uncontrolled and the temperature rise reaches 4.4 °C (8.0 °F), Earth could no longer support a large human population.

Some might think that the present 1.1 °C temperature rise is insignificant, but from a process control perspective it is not, because considering the immense mass of our planet, it represents the accumulation of gigantic amounts of heat. Therefore, this rise from 15 °C to 16.1 °C is a temendous upset to this heat balance process.

How do we know if CO2 is the cause?

Before reaching any conclusions, a good process control engineer will check the reliability of the measurements. In case of the atmospheric concentration of CO2, the data for the past half-century is highly reliable, as the measuremnents were made by instrumental means. The rest of the data, which goes back to when the earliest Neanderthals evolved about 200,000 years ago, was obtained by ice core drilling. This involves drilling down to some 3,000-4,000 feet, crushing the drilled ice samples under vacuum, and expanding the gas into a pre-evacuated sampling loop, where it is analyzed by gas chromatography. As this drilling process was repeated many times and in many locations, with little variation in the results, this data can also be considered reliable.

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In my analysis, I am not considering earlier data, because I do not have enough confidence in their accuracy. Those measurements, going back to millions of years, are usually based on detecting the composition of gases trapped in crushed stone samples. While in my conclusions I do not depend on them, I should mention that all these studies agree that today's CO2 concentration of 400 ppmv (parts per million by volume) has never been reached. Therefore, I can say with reasonable confidence, that the CO2 concentration in our atmosphere has not exceeded 280-295 ppmv during the past couple of million years.

In view of the above, I would conclude that although many other variables contribute to global warming, the existance of a direct relationship between global temperature and atmospheric CO2 concentration is unquestionable (Figure 1).

During the past 50 years, both the rate of rise of CO2 concentration and the rate of temperature rise increased drastically faster than in previous centuries (Figure 2). Based on this data, process control professionals would conclude that, because of the capacity and inertia of this process, the temperature will continue to rise even after the CO2 concentration is reduced. In addition, the rate of reduction in this concentration will be slow, because the residence time of the CO2 in the atmosphere exceeds a decade or more.

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On the other hand we would also conclude that if a global temperature rise of, say, 2 °C is reached, this will also increase the amount of heat radiated back into space by an immense amount (0.5 to 0.75 W/m2). Therefore, eventually the energy balance would be reestablished, but at an even higher temperature.

The various scientific models suggest that if the CO2 concentration is reduced to about 345 ppmv, this can limit the global temperature rise to 2 °C. This I disagree with! It seems to me that this conclusion does not sufficiently consider the tremendous inertia and "dead time" of this process, and therefore our target should be 295 ppmv and not 345 ppmv. The 295 ppmv concentration was not exceeded during the past million years, and therefore, the energy balance of the planet will not be reached until we reach it again. I also doubt the acceptability of the continued use of fossil fuels even for only a few decades because my crude calculations suggest that even if we stopped using them today, it is already inevitable that the sea levels will already rise some 4.5 - 6.0 m (15-20 feet).

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About the Author

Béla Lipták | Columnist and Control Consultant

Béla Lipták is an automation and safety consultant and editor of the Instrument and Automation Engineers’ Handbook (IAEH).