Mr. Liptak,
You wrote about the potentials of process control in modeling and predicting the performance of non-industrial processes like the economy. Could the laws of process control be also used to estimate the rate and consequences of global warming?
Harold Crowney
HCrowney@aol.com
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I did discuss some aspects of global warming when I wrote about the process dynamics of the Gulf Current (http://www.controlglobal.com/articles/2006/002.html ) and also wrote a book titled „The Post-Oil Energy Technology”, which also included a discussion of the rates and time constants of global warming.
One can look at this process as one which started about 2 billion years ago when the atmosphere begun to change from a reducing (CO2) to an oxidizing one (O2). This is the time when climate evolution started and life appeared on the planet. The atmospheric concentration of O2 stabilized at around 21% and it’s CO2 content never increased over 280 ppm during the last couple of million years, but during the industrial age “greenhouse gases” were admitted into the atmosphere causing the CO2 content to rise to 360 – 380 ppm and this concentration is projected to reach 510 ppm by the turn of the 21st century.
Oxygen Content of Earth's Atmosphere
It seems that life depends on the presence of liquid water (which can exist only between 0 and 100˚C) and on the presence of an atmosphere that protects life from both ultraviolet radiation and extreme temperatures. Weather is the state of the atmosphere that results from a number of processes. One of these processes is the heat balance of the planet.
Global temperature is a somewhat self-regulating process, because as the heat input of the planet increases, the excess heat is removed by increased vaporization of the oceans and increased melting of the polar ice caps and glaciers. Melting and vaporization both increases the overall water circulation on the planet (storms, rain, floods), while increased vaporization also dries land areas, increasing the frequency of forest fires, water shortages and desertification.
While the melting of the ice requires heat and therefore temporarily cools the planet, it has the reverse effect in the long run, because ice and snow reflect more radiation back to space than does water. The reflection coefficient, the bond albedo (29% of the solar radiation received is scattered back into space) and as ice melts, that number drops.
Therefore, water serves as the natural temperature controller of the planet (increased melting and vaporization when the planet warms) but this thermostats can only increase its cooling effect so long that there is ice at the glaciers and at the poles. Once the ice is gone, global temperature will „jump”, because only the vaporization of the oceans will balance the heat input. While the overall planet warms, there will also be localized cooling caused by the stopping of ocean currents, such as the Gulf Current, which is a gigantic heat conveyor, moving the heat from the Equator to Europe and the east coast of the United States.
The heat input of the planet is received from the Sun and is a variable. Over the past few hundred years, there has been a steady increase in the numbers of sunspots and the Earth’s temperature has also increased in proportion to them by about 0.2 ˚C. On the other hand, -as shown by the figure below- during the last half century this process reversed, solar activity was dropping while the temperature of the planet increased.
Temperature vs Solar Activity
Global average of „insolation” per square meter and the corresponding global temperature variation since data been kept.
(http://www.skepticalscience.com/solar-activity-sunspots-global-warming.htm).
For the dynamics of the atmospheric heat balance process, we have fairly good historical data concerning the dynamics and effects of hurricanes, wind, rain, clouds, CO2 content, smoke, etc. The energy content of a larger hurricane approaches the energy consumption of the United States for about a year and serves to equalize the air temperature in the stratosphere. As far as the dynamics of the thermal processes on the continents and in the oceans the inertia and time constants of the process are much greater and take much more energy to move or reverse.
So what are the variables (the control valves if you wish) that can influence the operation of this heat transfer control loop? What can mankind manipulate (accidentally or intentionally) to lower and stabilize the global temperature?
- We can lower the amount of the incoming solar heat by introducing large quantities of solids into the atmosphere to block the Sun’s radiation. This can occur due to natural causes nuclear wars, large fires or volcanic activity.
- Changing the reflectivity of the surface of the planet by making roofs and road surfaces more reflective.
- Rebalancing animal and plant life on the planet by the introduction of gigantic algae farms in the oceans or other means.
- Lowering the CO2 concentration of the atmosphere by gradually replacing fossil fuels by solar-hydrogen and other renewable energy sources.
It seems that the simplest variable to manipulate is to gradually stop the burning of fossil fuels. This we can do voluntarily and in a planned manner on the time frame dictated by the process control model) or se can let nature do it for us as we fossil fuels are exhausted. Naturally, the consequences of the second can be drastic and can possibly cause the collapse of human civilisation (turn the process into a batch one).
Béla Lipták
