Global Climate Change

Global and Domestic Carbon Dioxide Emissions & their Effect on Climate Change

Executive Summary
The circumstances surrounding global climate change and global warming will continue to be argued over for years. The emissions of greenhouse gases cannot be blamed on any one industry or fossil fuel. Of the warming commitment, coal combustion contributes globally 30% of the CO2 emission and about 15% of the total infrared absorbing gas pledge.

Attempts have been made in determining an adequate technological remedy, like CO2 scrubbing, but neither the uses nor the storage facilities exist for such an effort. The long term solution lies in a weaning of fossil fuels in favor of renewable sources such as biomass and solar.

Overview
The United States and the World face a dilemma whose result, if left unresolved, may severely impair life as humans know it on this planet. The problem lies in the near absolute reliance on a carbon-combustion economy [1] to provide us with heat, electricity, manufactured goods, and global transportation. As a result of the liberation of the chemical energy held in the bonds of hydrocarbon fuels, millions of tons of stable infrared absorbing gases are spewed out into the atmosphere with little regards toward emissions control or future removal. These gases form a blanket over the surface of the earth, such that the heat buildup up due to incident solar radiation cannot escape back into space, and a net warming of the earth results.

The massive climate change or “global warming” scenario caused by the so called “greenhouse gases” such as carbon dioxide (CO2), methane (CH4), and chlorofluorocarbons (CFC’s) that absorb electromagnetic radiation in the infrared, is not without dispute. Arguments ceased several years ago on the possibility of the trend, and now conversations revolve around the time necessary for the warming inception. In fact, without the natural greenhouse effect, if no trace gases existed in the atmosphere, the mean earth temperature would be 32°C (58°F) less [2], thus below the freezing point of water, and for life on earth. Current sophisticated computer climate change models conclude that by 2050 or before, the level of CO2 in the air will double from 18th century levels and leave a 4°C (7°F) increase on the mean earth temperature [2]. Though the temperature variation appears small, no change of this magnitude has ever been recorded in the geological time history of the planet, and when change has occurred by +/-1°C (+/-2°F) on the geologic record, the progression occurred over centuries if not millennia. We face a catastrophic global temperature increase of 1°C (2°F) per decade, without knowledge of the alterations that may occur in weather, precipitation patterns, ocean levels, and to life in general.

Carbon Dioxide Emissions And The Warming Time Frame
The issues surrounding the possible adverse effects of increasing the concentration of carbon dioxide (CO2) in the atmosphere require serious attention and action. A proper examination of the event requires a methodical survey of the historical trends before and after the advent of the carbon-combustion economy.

Historical Records
Accurate measurements of the atmospheric concentration of CO2 began at the Mauna Loa Hawaii observation site in 1958. CO2 levels started at 315 parts per million by volume (ppmv) and over the last 35 years increased at 1 ppmv per year to the current 351 ppmv reading. Information on the CO2 concentration before 1958 comes from ice core samples. Data from Vostok, East Antarctica yielded a chronological record of the last 160,000 years that showed considerable natural variation in the CO2 ppmv in concert with global geologic disturbances. Over the long record, the magnitude of CO2 has varied from 200 ppmv during a glaciation to 285 ppmv signaling a warming trend [3].

From 1958 to 1986 an estimated [3] emission of the equivalent of 56 ppmv of CO2 due to fossil fuel combustion, left an airborne accumulation of 31 ppmv, or 55% of the emissions remained in the atmosphere, the rest primarily sequestered by the oceans.

Not only has the CO2 concentration increased over time, but the total amount of carbon-combustion has also escalated annually. Using information on the growth of developing countries, population expansion, and future energy requirements fossil fuel consumption may increase by 3.6% annually [3] if no limit on CO2 emissions is enforced. To stabilize CO2 levels at today’s value would require a reduction of 50-80% [4] to follow the decreased capacity of the ocean uptake as time continues.

Of the global flows of CO2 in the biosphere and cryosphere, man’s contribution is relatively small. The respiration and photosynthesis of land and aquatic life dominates the exchange of CO2 pathways.

Other Greenhouse Gases and Life Span
Carbon dioxide is not the only participant in global change, in fact it is a very weak absorber of infrared radiation. The most important greenhouse gas is water vapor, as it absorbs over a long range of infrared wavelengths [5], and the large predicted changes in temperature will be a result of positive feedbacks to shift more water vapor into the atmosphere. Contributions from other species are summarized below[4] [6].

Also listed below is the typical life span of the atmospheric gases. Unfortunately, atmospheric CO2 values do not hover around some fixed equilibrium position. The biosphere will not change to return to a past equilibrium value (though we witness an inertia to change by uptake by the oceans), rather those species that can be consumed in atmospheric chemical reaction like CH4 will, whereas the CO2 will stay at its elevated concentration for perhaps millions of years.

Gaseous Species Responsible for Greenhouse Effect
Species
Percent Contribution
Life Span
CO2
55%
500 years
CH4
15%
7-10 years
N2O
6%
140-190 years

Climate effects
The possible effects of global climate change require validation through the use of a General Circulation Model. With a doubling of CO2 concentration to 600 ppmv expected global mean temperature may rise between 1.5-9°C (3-16°F), depending on the climate model and the various positive and negative feedback mechanisms, precipitation levels may increase 7-15%, and sea level may climb from between 10 to 100 cm. A 4.5°C (8°F) mean temperature rise does not suggest a uniform increase of temperature unilatitudinally. The tropics will cool due to increased cloud formation and the mid latitude temperature will increase from 6 to 9°C (11 to 16°F) and the polar region from 9-15°C (16 to 27°F). Accompanying the physical changes will be meteorological transformations. Tropical storms may double in intensity, fertile areas may become drought stricken, and a whole host of other climate based modifications yet to be discovered.

Seidel [7] reports on some of perhaps the beneficial consequences of the warming commitment. The increase in water vapor and CO2 could stimulate photosynthesis and plant growth in certain crops and increase precipitation. The rise in temperature could improve the climate in high altitude areas and reduce heating costs worldwide. The feature of heating also brings along its conjugate: cooling or air-conditioning. By the year 2015 the predicted global average 1°C (2°F) increase will raise air-conditioning loads 10 to 20% [8] requiring new generating facilities.

Fossil Fuels
The consumption of fossil fuels has grown steadily from the 1850’s. The United States contributes the greatest amount of the global CO2 at 22% [8] in a manor reflecting in sector breakdown to worldwide emissions.

Total U.S. Carbon Dioxide Emissions Release by Sector
Sector
Percent Contribution
TransportationIndustry
24%
Electric Power Generation
>35%
>Residences
>11%

The division of fossil fuel consumption and total carbon emissions, as shown in Table 2 [4], demonstrates the areas that can reduce CO2 emissions. The actual contribution of CO2 to the atmosphere per unit energy output is a function of the carbon to hydrogen ratio and is shown in Table 3 [3]. Coal has nearly double the CO2 output of natural gas.

Table 2. Contribution of Fossil Fuels to CO2 Emissions
Fuel
Percent Contribution
Primary Use
Oil
48%
Transportation
Coal
34%
Electricity
Natural Gas
18%
Various uses

Table 3. Mean CO2 Emission Rate for Standard and Synthetic Fuels
Fuel
Emission Rate (g C/GJ)
All values
Natural Gas
14
are the mean levels
Oil(Liquid Fuel)
19
ignoring product
Bituminous Coal
24
mix

Typical data on the extractable reserves of both natural gas and oil place the phase out date between 30 to 40 years, but for coal an estimated 200+ years. From a fossil fuel availability standpoint coal could last for a long time.

CO2 Mitigation Strategies
From a typical coal fired plant, CO2 makes up about 15% by volume [9] of the effluent gas. Several techniques are available to address the release of CO2 in a stationary combustion system. Present science has a method to scrub away the CO2 via a chemical absorbent. A likely candidate is Monethanolamine (MEA) which absorbs CO2 via the

R-NH2 + H2O + CO2 —> R-NH3HCO3

reaction at 27°C (81°F) and then will desorb in the reverse reaction at 150°C (302°F). The result of the additional energy to release the absorber and to quench the gas would reduce a typical power station from a 40% thermal efficiency to 29%. A better approach would be in a Integrated Gasification Combined Cycle (IC) Plant where isolation of the CO2 would take place in a intermediate gas-shift reaction reducing thermal efficiency from 44% to 38% [9]. The additional energy consumption come from the necessary dehydration and compression of the CO2 for transport.

If separation of the carbon dioxide proved possible, the additional disposal of the gas would likely become the greater problem. Considering the enormous volume required for storage, two probable location are either the deep ocean or an evacuated natural gas field. Several industrial processes could use CO2 in production, but not nearly to the extent of current output [10].

Deep ocean disposal can be considered only a temporary solution [11], on the order of centuries, because the ocean waters do circulate. The more likely near term solutions would include a program of increased efficiency in energy conversion, energy utilization and energy conservation, and an active development of alternative energy studies like fuel cell and solar research. Fuel switching will also reduce CO2 emissions by changing from a high CO2 releaser like coal to a low CO2 emitting fuel like natural gas.

Conclusion
Short-term responses would require an increased efficiency and attention to conservation to all sectors. For a coal fired plant, a 5% increase in thermal efficiency corresponds to a 15% reduction in CO2. The more long-term strategy must include fuel switching to lower CO2 content and finally to a renewable source such as solar-hydrogen or biomass.

Many of the effects that may occur under a climate change scenario remain unknown. Policy makers continue to call for additional studies, whose conclusions become more steadfast in their results. Current models demonstrate the need to strengthen research into sustainable energy alternatives to the fossil fuel economy. The world awaits results to further information gathered on greenhouse warming, but the real global experiment continues to run on unhindered.

Literature
[1] Skelton, L. W. The Solar-Hydrogen Energy Economy: Beyond the Age of Fire. Van Nostrand Reinhold Company, New York: 1984.

[2] Kellogg W. W. “Energy Generation: The Basic Cause of Current and Future Climate Change.” Hydrogen Energy Progress VIII. Edited by T. N. Veziroglu. Pergamon Press, New York: 1990. Volume 1, Pages 145-161.

[3] Lashof, D. A. Policy Options for Stabilizing Global Climate. Hemisphere Publishing Corporation, New York: 1990.

[4] Changing By Degrees: Steps to Reduce Greenhouse Gases. U.S Congress. Office of Technology Assessment. U.S. Government Printing Office, Washington D.C.: 1991.

[5] Thurlow, G. Technological Responses to the Greenhouse Effect. Elsevier Applied Science, London: 1990.

[6] Lyman, F. The Greenhouse Trap. Beacon Press, Boston: 1990.

[7] Seidel, S. Can We Delay a Greenhouse Warming? U.S. Environmental Protection Agency, Washington D.C.: 1983.

[8] Torrens, I. M. “Global Greenhouse Warming: Role of the Power Generation Sector and Mitigation Stategies.” Energy Technologies for Reducing Emision of Greenhouse Gases. Proceedings of an Experts Seminar Paris 12th-14th April 1989. Volume I and II. Organization for Economic Co-Operation and Development/International Energy Agency, Paris: 1989.

[9] Hendriks, C. A. “The Recovery of Carbon Dioxide from Power Plants.” Climate and Energy: The Feasibility of Controlling CO2 Emissions. Kluwer Academic Publishers, Dordrecht, Netherlands: 1989.

[10] Aresta, M. “Carbon Dioxide Recovery and Utilization in the Synthesis of Fine Chemicals and Fuels: A Strategy in Controling the Greenhouse Effect.” Energy Technologies for Reducing Emision of Greenhouse Gases. Proceedings of an Experts Seminar Paris 12th-14th April 1989. Volume I and II. Organization for Economic Co-Operation and Development/International Energy Agency, Paris: 1989.

[11] de Baar, H. J. W. “Storage of Carbon Dioxide in the Oceans.” Climate and Energy: The Feasibility of Controlling CO2 Emissions. Kluwer Academic Publishers, Dordrecht, Netherlands: 1989.

Additional Resources
MacDonald, G. J. The Long-Term Imacts of Increasing Atmospheric Carbon Dioxide Levels. Ballinger Publishing Company, Cambridge, MA: 1982.

Jager, J. Climate and Energy Systems. A Review of their Interactions. John Wiley & Sons, New York: 1983.

Confronting Climate Change. National Research Council. National Academy Press, Washington, D.C.: 1990.

Williams, J. Carbon Dioxide, Climate and Society. Pergamon Press, Oxford: 1978.

Flohn, H. Possible Climate Consequences of a Man-Made Global Warming. International Institute for Applied Systems Analysis, Laxenburg, Austria: 1980.

Clark, W. C. Carbon Dioxide Review: 1982. Clarendon Press, Oxford: 1982.

Energy and Climate Change. Report of the DOE Multi-Laboratory Cimate Change Committee. Lewis Publishers, Chelsea, MI: 1991.

Smith, I. M. Carbon Dioxide- Emissions and Effects. IEA Coal Research, London: 1982.

Energy Technologies for Reducing Emision of Greenhouse Gases. Proceedings of an Experts Seminar Paris 12th-14th April 1989. Volume I and II. Organization for Economic Co-Operation and Development/International Energy Agency, Paris: 1989.

Walsh, J. H. ÒThe Selection of Energy Technologies Under Conditions of Restricted Carbon Emissions.Ó Energy Technologies for Reducing Emision of Greenhouse Gases. Proceedings of an Experts Seminar Paris 12th-14th April 1989. Volume I and II. Organization for Economic Co-Operation and Development/International Energy Agency, Paris: 1989.

Bach, W. Carbon Dioxide. Current Views and Developments in Energy/Climate Research. D. Reidel Pulishing Company, Dordrecht, Holland: 1983.

Bach, W. Our Threatened Climate. D. Reidel Pulishing Company, Dordrecht, Holland: 1984.

Changing Climate. Report of the Carbon Dioxide Assesment Committee. National Research Council. National Academy Press, Washington, D.C.: 1983.

Energy and Climate. Geophysics Study Committee. National Research Council. National Academy Press, Washington, D.C.: 1977.

Ozone Depletion, Greenhouse Gases, and Climate Change. Proceding of a Joint Symposuim by the Board on Atmospheric Sciences and Climate and the Committee on Global Change. National Research Council. National Academy Press, Washington, D.C.: 1989.

Green, A. E. S. Greenhouse Mitigation. The American Society of Mechanical Engineers, New York: 1989.

Liss, P. S. Man-Made Carbon Dioxide and Climate Change: A Review of Scientific Problems. Geo Books, Norwich, England: 1983.

Carbon Dioxide and Climate: A Scientific Assessment. Climate Research Board. Assembly of Mathematical and Physical Sciences. Naional Academy of Sciences, Washington, D.C.: 1979.

Enting, I. G. Calculating Future Atmospheric CO2 Concentrations. CSIRO Division of Atmospheric Research Technical Paper No. 22, Australia: 1991.

Okken, P. A. Climate and Energy: The Feasibility of Controlling CO2 Emissions. Kluwer Academic Publishers, Dordrecht, Netherlands: 1989.

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