Why do we have global warming?

IN THE past, life on Earth was sustained by solar energy alone (See Figure 1 below). This inexhaustible and clean energy was used by the world’s green plants, which converted atmospheric carbon dioxide into organic materials, while releasing oxygen into the atmosphere. Animal life completed this cycle, obtaining their muscle energy by oxidizing the organic materials produced by the plants, while inhaling oxygen and exhaling carbon dioxide. Therefore, so long as the global density of plant and animal life was balanced, the carbon dioxide content of the atmosphere remained constant.

In the present, modern man needs more energy for comfort, transportation, and similar purposes. The energy obtained from green plants is no longer sufficient. Consequently, they’re supplemented by exhaustible hydrocarbon fossil deposits to meet the increased energy demand. Naturally, burning the planet’s fossil energy deposits increases the carbon dioxide and other gas concentrations in the atmosphere. These greenhouse gases block the passage of thermal radiation from Earth back into outer space, and reduce the global heat loss. The result is global warming. It is like placing a blanket over the planet.

The Solution
There is little question that the only inexhaustible energy source is the Sun. Solar energy can be collected at the equator—on land in the Sahara or on floating islands in the ocean—and can be converted into electric energy by photocells. This electricity can be stored in the form of chemical energy by splitting the water into oxygen and hydrogen (electrolysis). The oxygen can than be released into the atmosphere (just as plants do), while the liquefied hydrogen can be distributed, just as LNG is distributed today.

When the hydrogen is received by users, fuel cells can reconvert its chemical energy back into electricity. In the future, hydrogen can fuel our homes, power plants, and transport vehicles, just as it fuels spacecrafts today. This “hydrogen economy” would not only be clean and inexhaustible, but would also eliminate global warming by stopping the generation of carbon dioxide.

An indirect way of using solar energy is to produce hydrogen from agricultural products, such as glucose or ethanol. This approach is inferior to using water as the source of hydrogen because generating hydrogen from organic materials again results in greenhouse gases and carbon dioxide, which further contribute to global warming. By contrast, in the process described in Figure 1, solar energy is stored in hydrogen’s chemical energy, but only water and no greenhouse gases are produced when it’s reconverted into electric energy.

The Time Factor
Some argue that we have plenty of time because fossil fuels will last for generations, and because the causes of global warming are debatable. Those who share this viewpoint are likely to promote more oil exploration, and building more nuclear and coal-burning power plants. They’re likely to propose waiting until we either run out of all these resources, or until the consequences of nuclear waste accumulation and/or global warming become intolerable.

We live in an irresponsible age: the population of the planet has increased 500% during the last century, the stockpile of nuclear warheads is still staggering, and our government’s budget is balanced at the expense of coming generations. It’s consistent with this attitude of irresponsibility to overestimate the time available to convert to a clean and inexhaustible energy source. Unfortunately, as was shown in the discussion of the processes that guide the behavior of ocean current, the time available to make this decision, can be much shorter than we think.

References:

• Delworth, T.L., Mann, M.E., “Observed and Simulated Multidecadal Variability in the Northern Hemisphere,” Climate Dynamics, 16, 661-676, 2000.
• Emanuel, K. (2005), “Increasing Destructiveness of Tropical Cyclones Over the Past 30 Years,” Nature, online edition, July 31, 2005, doi: 10.1038/nature03906
• Goldenberg, S.B., C.W. Landsea, A.M. Mestas-Nuñez, and W.M. Gray, “The Recent Increase in Atlantic Hurricane Activity: Causes and Implications,” Science, 2001, vol. 293, pp. 474-479.
• Kerr, R.A., “A North Atlantic Climate Pacemaker for the Centuries,” Science, vol. 288, p. 1,984-1,986.
• Knutson, T. K., and R. E. Tuleya, 2004: Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. Journal of Climate, 17(18), 3477-3495.

[Editor’s note: this is the third installment of Béla Lipták’s three-part series on using process control principles to understand and perhaps control global warming. The first part, “A Process Only Mankind Can Control, Part 1,” appeared in CONTROL, Jan. ’06. The second part, “Can Process Control Stabilize Global Warming?” appeared in CONTROL, March ’06.]