Causes of Increased CO₂

We know the reason carbon dioxide is increasing in the earth's atmosphere. Deforestation is one of these causes, although not the main cause. Figure 7 shows the current annual release to the atmosphere of teragrams of carbon by several different countries due to deforestation. Brazil contributes the most, followed by Indonesia, Columbia, and other mostly tropical countries. It is important to recognize that developed countries, like the US and European nations do not appear on the chart of current deforestation. These countries have, in fact, reduced their forest area, but did so over the last few hundred years. Major wildfires also make periodic contributions to atmospheric CO₂.

Another source of carbon dioxide in the earth's atmosphere is the emission from cement plants (Figure 8). Carbonaceous material used for making cement releases significant amounts of carbon dioxide in creating the final product. This source of carbon dioxide will come up again in our discussion of sustainable development, since cement for roads, bridges, buildings, power and manufacturing plants is a key ingredient for economic development. Of particular interest are countries such as China and India that have such enormous potential for development. Global production of cement puts about 1.5 billion metric tons of CO₂ into the atmosphere annually.

The major cause, by far, for the rise in concentrations of carbon dioxide in the earth's atmosphere is the burning of fossil fuels. Figure 9 shows the fossil fuel emissions in gigatons per year as a function of time. Emissions before the 1860s were well below 1 gigaton per year and rose quite slowly until the middle of the present century. Since the late 1940's and early 1950's, this curve has risen dramatically to present emission levels of about 6 gigatons per year. Figure 9a reveals the contribution to global CO₂ emissions by various countries.

A break-down of the kinds of fossil fuels contributing to this rise shows that coal use has increased steadily over the last 100 years and is increasing quite significantly at present. Use of oil for heating, manufacturing, and automobiles started later but also is increasing at a rapid rate. Use of all types of fossil fuels is increasing, and this trend will likely continue well into the future. Global distributions of emission sources are compiled by the Carbon Dioxide Information Analysis Center.

A calculation of emissions per mile for travel by automobile and by air shows that such travel adds about 0.25 to 0.50 kg/mile of carbon dioxide to the atmosphere.

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