The following graph shows the variations in global temperatures, going back one-million years. It shows that warm periods occurred roughly every 100,000 years, with colder periods in between. It was during those cold periods that the great continental ice sheets advanced, spreading over much of the North American continent each time ([On-line], 1998).
Figure 1 Variations in Global Temperatures Over the Last Million Years ([On-line], 1998).
The next graph shows how climates have changed in the past 1000 years. It shows that around 800 years ago, there was a 300-year warm spell. This was a time when Greenland was actually green (Europeans were farming there), and grapes and other warm-climate fruits could be grown on the British Isles ([On-line], 1998).
Figure 2 Global Temperatures Over the Last 1000 Years ([On-line], 1998)
The graph above also shows that around 400 years ago, the global climate was approximately 1-2 degrees colder than now. It was a time when winters were longer, and glaciers advanced dramatically. The Vikings had to abandon their farms on Greenland, and withdraw from Eastern Canada, where they had also settled. This period is known as the “Little Ice Age.” It is clear that climates change naturally on their own. What has caused these changes? Scientists all over the world are studying this problem, and are coming up with many theories. Many natural events appear to have altered global climates, including meteorite impacts, volcanic eruptions, and changes in the compositions of the earth’s atmosphere ([On-line], 1998).
The most important factor seems to be composition of the atmosphere, which affects the intensity of the Earth’s greenhouse effect. Scientists now know that many changes in past climates seem to occur at the same time that changes in the concentration of CO2 also occurred. When the Earth’s average global temperature has risen or fallen, CO2 concentrations have moved in a similar pattern ([On-line], 1998).
The last graph shows changes in temperature have been mirrored by changes in the two important greenhouse gases, carbon dioxide and methane. It shows that for every peak in average global temperature, there was a corresponding peak in greenhouse gases ([On-line], 1998).
The relationship between global temperatures and composition of the atmosphere has scientists extremely concerned. Human activities are rapidly increasing the concentration of greenhouse gases in the atmosphere. In fact, scientists now believe that if anthropogenic (human-caused) emissions of greenhouse gases are not significantly reduced, the Earth will warm at a rate faster than at any time in the 10,000 years that represent human history ([On-line], 1998).
Climate is usually something humans take for granted. It changes far too slowly for us to notice on a day-to-day basis. But by looking at long-term climate records, and with new techniques for determining ancient climates from ice, sediments, and other natural deposits, we can see climates have changed dramatically in the past. We can also see that some of the changes humans are making to the atmosphere and to landscapes are beginning to have noticeable effects on global climates. We now have to think about protecting the Earth’s climate system the same way we do about protecting other important parts of the environment, like water, air and soil ([On-line], 1998).
Figure 3 Location of t he Principle F ire Events in 1 998 ([On- l ine], 1998)
Conclusions
Fire provides the material well-being of the people in the industrial countries of the world. Heat from the burning of fuel converted into electrical and mechanical energy does practically all the work of these economies. However, the world’s population has a fire problem. Americans and Canadians lose property and life to fire at twice the rate of people in comparable circumstances in other industrial nations. The table below illustrates the fatalities due to fire in various nations (Payne, 1989, 56).
Table 1 Fire Caused Fatalities in Various Nations (Deaths per 100,000 pop.) (Payne, 1989, 56)
Nation 1974 1976-78 Latest Report
Canada 3.6 3.2 2.9
United States 2.9 2.9 2.8
Sweden 1.6 1.5 1.6
Japan 1.5 ——– 1.5
United Kingdom 1.5 1.5 1.5
France 1.5 1.5 1.5
Australia 1.5 ——– 0.8
Germany 0.9 0.9 0.9
Switzerland 0.7 0.6 0.7
References
Compton’s Interactive Encyclopedia: On compact disc (1996) [CD-ROM].
Lyons, John W. (1985). Fire. New York: Scientific American Library.
Payne, Charles A., Falls, William R., & Whidden, Charles J. (1989). Physical Science (5thed.). Iowa: Wm. C. Brown Publishers.
Whelan, Robert J. (1995). The Ecology of Fire. Great Britain: Cambridge University
Press.
United Nations Environment Program. [On-line]. Available:
http://www.grid.unep.ch/fires/
[On-line]. Available:
http://www.piad.ab.ca