Environmental Indicators - 6 Carbon Dioxide Emissions
The environmental indicators discussed in this section are (1) carbon dioxide emissions, (2) oil spills, (3) pesticides, (4) toxic releases, and (5) wildlife. These are often cited as measures of the state of the environment but we class them as secondary because they provide information about environmental quality that is, at best, indirect. In some cases, such as carbon-dioxide emissions, it is unclear whether the indicator contributes to an environmental problem. In other cases, such as wildlife, the data available make it difficult to draw reliable conclusions. As a result, the secondary indicators presented in this section are not included in the index of environmental quality presented at the end of the report.
6 Carbon Dioxide Emissions
Carbon dioxide (CO2) is a vital nutrient for plants. Oceans absorb and produce CO2 in great quantities through a complex cycle and store about 50 times more carbon than does the atmosphere.1 The combustion of fossil fuels by humans also generates CO2.
Emissions of CO2 correlate with fluctuations in Gross Domestic Product (GDP) (figure 6.1). Emissions of CO2 in Canada rose with economic growth until the 1970s, then levelled off before declining in the early 1980s. Recently, emissions have risen again.
Figure 6.1 GDP compared to CO2 Emissions: Trends in Canada
Source: Environment Canada National Environmental Indicator Series, 1999. OECD 1999. Canadian Economic Observer 1999.
It has been suggested that human-induced CO2 emissions are linked to global warming. As a result, controlling CO2 emissions has been the subject of many recent policy debates. In order to understand fully the popular debate about global warming, one must appreciate the distinction between the greenhouse effect and the enhanced greenhouse effect. Scientists agree that there is a greenhouse effect that causes the earth to be warm. This effect occurs because greenhouse gases such as carbon dioxide, water vapour, nitrous oxide, and methane are transparent to the short wavelength radiation from the sun but opaque to the longer wavelength radiation emitted from the earth. In simple terms, greenhouse gases trap the heat from the sun and this warms the earth.
The popular debate revolves around the question whether humans, through their additions of greenhouse gases to the atmosphere,2 enhance the greenhouse effect that occurs naturally and, thus, contribute to global warming. The theory of enhanced greenhouse effect gained many advocates in the 1950s but lost popularity in the 1960s and 1970s when average temperatures fell. During the 1970s, the idea that pollution was causing global cooling by reflecting sunlight away from the earth's surface was supported by many who now promote the theory of the enhanced greenhouse effect.
Although some now claim that the increase in CO2 levels in the atmosphere will cause a catastrophic warming, there are many credible challenges to this theory. In the face of the uncertainty within the scientific community about the link between human additions of CO2 to the atmosphere and global warming and in the absence of a proven link to global warming, CO2 cannot be considered a pollutant but, at most, a secondary indicator of environmental quality.
The scientists who criticize the theory of global warming possess three powerful lines of attack on the apocalyptic theories: the inadequacy of the computer models being used to forecast future temperatures, the evidence from actual temperature records, and the strength of competing hypotheses that explain warming trends but are currently under-reported and insufficiently considered by policy makers.
The inadequacy of the computer models
It is important to realize that current projections of global warming and policy recommendations for dealing with the predicted crisis are based on computer models that try to forecast future temperatures based on a number of assumptions. At the present time, these computer models are incapable of modeling the atmospheric system completely. Large gaps in understanding about the way important variables such as oceans and clouds affect climate, and how the effects of these variables change with additions of CO2 make the predictions of these models unreliable.
In fact, the computer models cannot even replicate what has already happened to temperatures. For example, according to the model used by the Intergovernmental Panel on Climate Change (IPCC), the northern hemisphere should have warmed between 1.3° and 2.3° Celsius since the beginning of the century. It has not. For the northern hemisphere, the warming measured at ground-based stations is about 0.6 degrees Celsius--less than one-third the warming that the IPCC's model predicted.
Evidence from temperature records
The second major criticism of the theory that temperatures are likely to rise as a result of increasing CO2 emissions and cause dramatic damage to the environment is that temperature records do not support a strong link between CO2 emissions and warming. According to ground-level temperature records, there has indeed been an increase in temperature over the past 100 years. Most of this increase, however, occurred before 1940; in other words, most of the increase in temperature occurred before the main input of human-induced CO2 emissions. In addition, records from the satellites that have been measuring temperatures in space since 1979 do not support the hypothesis that the earth is warming. While the climate models produced by computers predict that there should have been some warming over the past 20 years, the satellite data show no warming. The evidence does not support the predictions of the models. It is considered a problem in any scientific discipline when the evidence contradicts a theory and such a discrepancy should lead to a re-evaluation of the models.
Other explanations for temperature change
There are other viable explanations that do not rely upon increased CO2 emissions to explain atmospheric temperature change. Unfortunately, these explanations have not received widespread media attention.
Some scientists hypothesize, for example, that much of the temperature fluctuation can be explained by changes in the brightness of the sun--something that is obviously beyond human control. Sallie Baliunas, a scientist at the Harvard Center for Astrophysics, explains:
Most of the warming early in this century, then, must have been due to natural causes of climatic change, and these natural causes must be understood in order to make an accurate assessment of the effect upon climate of any human activities that may have been added to the natural changes . . . One possible natural cause of climatic change is variation in the brightness of the sun. (Baliunas and Soon: 81)
The processes of "fingerprinting" various mechanisms of climatic change and projecting climatic change requires knowing all the relevant factors, both those that are natural and those that are the result of human activity. And, these factors must be considered simultaneously in a model. Once such a model is verified, then only can each mechanism be identified. Since the mechanisms of climatic change are not fully known--as we have shown, the question how the sun affects the climate is unresolved--and the models have not been verified, fingerprinting is not yet possible. (Baliunas and Soon: 86-87)
It is clear that a great deal of uncertainty surrounds the issue of climate change and many important questions remain unanswered. Are we experiencing a trend towards global warming? Do humans contribute to the trend through the emission of greenhouse gases? How significant is the human contribution? Would global warming cause widespread problems?
Some argue that we must take drastic regulatory action to control greenhouse gases without delay. However, because of the uncertainty and the unanswered questions, this is a simplistic approach to policy. In fact, we cannot afford to take action until we are reasonably certain that we have a problem because taking drastic measures to control greenhouse gases will come at the expense of other social objectives.
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