Global Warming
Why is CO2 a problem?
In fact, carbon dioxide is not a problem. Carbon dioxide is one of the reasons that life can exist on earth. Without carbon dioxide in the atmosphere, the Earth could not support life because the temperature would be too cold and all the water would be frozen. Because carbon dioxide is a strong absorber in the infrared region of the spectrum, it absorbs heat radiating from the Earth and reradiates it back to the surface to warm the planet. This is the greenhouse effect [1] . It is a natural process that is essential to life. However, when there is too much carbon dioxide in the atmosphere, the greenhouse effect is intensified, causing an environmental problem. Before the industrial revolution, the concentration of carbon dioxide in the atmosphere was 280 ppm. From 1880 onwards, due to the increase in combustion of fossil fuels as an energy source, the concentration of CO2 has steadily risen at the rate of approximately 1.5 ppm/year to its current level today of 365 ppm(carbon dioxide is the natural end product of combustion). The concentration is expected to continue to increase unless the emissions from fossil fuel are curtailed or stopped all together. The Intergovernmental Panel on Climate Change (IPCC) estimates atmospheric concentration of carbon dioxide to rise to between 540 and 940 ppm by the year 2100. [2]
The rise in CO2 has been accompanied by a rise in the average mean temperature of the earth. Although it has remains a hotly debated topic, most experts tend to agree that the increased level of CO2 in the atmosphere is at least partly the cause of the temperature increase, known as global warming.
Among the critics of the negative effects of an increase in the carbon dioxide concentration in the atmosphere is Hugh W. Ellsaesser [3] . Ellsaesser argues that increasing CO2 is not a necessary condition for raising the mean global temperature, which in and of itself may not be a bad thing. In addition, he believes "that the climate models are over estimating the amount of warming for a doubling of carbon dioxide by at least 2- to 3-fold and that there are good reasons to believe that the exaggeration is even greater than this."
Idso, another dissenter, argues that the models overestimate warming by at least an order of magnitude based upon a simple extrapolation of data from the atmospheres of Mars and Venus. He also argues that increasing CO2 will naturally increase plant production, which is a natural sink for sequestering the CO2. [4] Arguing that increased plant growth will provide a sink for the increase in carbon dioxide, however, is somewhat misleading. First, eventually the carbon tied up in plants is returned to the atmosphere through the carbon cycle, so the carbon is not really removed from the atmosphere; its entry is just delayed. Second, many argue that the amount of land that would need to be forested to capture the amount of CO2 currently produced is ridiculously large and not at all feasible.
Black, another critic, offers that "normal range of temperatures is greater than those extremes which we have thus far caused, and that our changes are so small that we cannot fully evaluate their significance." [5]
The above examples are just a sampling of the disagreement that lingers over not just the negative effects of global warming, but whether global warming even exists. Despite, continued controversy, the general consensus is that global warming does exist and that it is a problem. This has lead the governments of the world to take action by forming the IPCC, developing the Kyoto Protocol, and numerous other resolutions and treaties.
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| source: Y. Ju Mae 427 Lecture 1 p.7 |
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| source: Y. Ju Mae 427 Lecture 1 p.8 |
How much is too much?
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| source: Lackner p.59 (12/2001) |
Annual world fossil fuel consumption is approximately 6 Gt of carbon and growing, which amounts to 85% of the total energy consumed. Right now some of the carbon emitted to the atmosphere ends up in other reservoirs, such as the ocean and biomass, because they are still equilibrating with the atmosphere. As soon as atmospheric levels are controlled, equilibrium will be reached and a larger percentage of the CO2 emitted will remain in the atmosphere. Therefore, the rate of emission is not as important as the overall level of carbon dioxide in the atmosphere. "Model calculations suggest that in order to fix the total carbon dioxide level in the atmosphere, emissions will have to fall below those of 1990 levels in a matter of a decade or two. Energy efficiency and reduced economic growth may slow down, but cannot prevent the inexorable rise of carbon dioxide levels. Holding CO2 concentrations constant at any acceptable level would require far more drastic emission reductions." The higher the level of carbon dioxide in the atmosphere that is considered acceptable, the longer time we will have to stop emissions, but the underlying problem will remain the same regardless of what is considered acceptable. [6]
What can be done?
Assuming the increasing level of carbon dioxide in the atmosphere and global warming is a problem, techniques are currently available and under development to stop, if not reverse, the earth's temperature rise. Millions and millions of dollars are spent each year on research and development for clean fuels such as hydrogen, wind, nuclear energy, and solar energy, technology to reduce emissions, technology to capture unwanted gases like carbon dioxide, and numerous other state-of-the-art methodologies. Right now it is widely agreed that the earth has enough fossil fuel deposits to last us for centuries. For example, estimates predict 10,000 Gt of coal are available (compared with the 6Gt annual consumption of fossil fuels). So until an alternate fuel source becomes economically viable, which will be extremely difficult due to the large infrastructure in place for fossil fuels, or the world energy demand significantly drops, which is highly unlikely, the world is going to continue to burn fossil fuels and emit carbon dioxide. Therefore, the environmental effects of the carbon emissions must be dealt with. There are a number of ways to handle the excess carbon dioxide.
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Use it - Several technologies are under development to utilize the millions of tons of carbon dioxide produced annually. Benson et al. suggest the following options for using captured CO2: develop new products that will have significant potential markets from captured CO2; utilize the CO2 for current polymer manufacturing, using ammonia, water, and the captured CO2 produce ammonium bicarbonate (NH4HCO3) fertilizer; or employ some genetic engineering to develop plants that produce more sturdy or economical carbon-based materials. [7] Because the technologies are not fully development, utilizing the CO2 will not help in the here and now. Also, if and when the technologies become fully developed and economically viable, there is some skepticism as to whether or not utilizing the carbon will have a substantial effect on the overall CO2 problem. "However, the options for turning CO2 into valuable products are extremely limited considering the fact that the volume of CO2 is very large. CO2 emissions in the US alone amount to about 20 t/year per person (EIA, 1998). This is more than three times per capita crushed stone consumption in the US. Considering the value of crushed stone today, transportation costs alone would make this option very unattractive. We can easily rule out carbon recycling in the form of plastics (Halman, 1993, Arresta, & Tomasi, 1997) or other organic compounds. The syntheses of nearly all carbon rich products which require substantial amounts of energy are usually far in excess of what has been extracted at the power plant." [8]
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Another option is to increase the storage of carbon by increasing the amount of photosynthesis taking place on earth. In other words, increase the earth's biomass. This is known as biological sequestration. This can be accomplished by planting more trees or ocean fertilization, which will increase the biomass production in the form of phytoplankton. It is widely agreed that the limiting nutrient in the ocean for stopping plant growth is iron. There are are a couple of techniques being developed to determine the best way to add iron to the ocean to increase phytoplankton production, which will increase carbon storage in the ocean. Both biological sequestration and ocean fertilization are areas with large amounts of research and may play valuable roles in solving the carbon dioxide problem. Both, however, do have their limitations, in that only so much land can be dedicated to growing trees and the ocean can only support so much phytoplankton. (Note: although biological sequestration and ocean fertilization are widely considered to fall under the category of carbon sequestration, for the purpose of this website we are only focusing on those forms of sequestration independent of living organisms i.e. storage of the carbon in chemical form .)
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The final option is to dispose of it. If you can't use it and you don't want it, what do you do with it? Throw it away! Well, we can't really throw it away since there is no such thing as a universal dumpster, but we can store it, hopefully permanently. That's where sequestration comes in. There are many ways to sequester carbon dioxide: oceans, mineral mines, geological formations. Just click to find out more!
