TEMPERATURE RISING
Chapter 2. Signs of Stress: Climate and Water
Lester R. Brown, Eco-Economy: Building an Economy for the Earth
(W.W. Norton & Co., NY: 2001).
Since agriculture began, the earth's climate
has been remarkably stable. Now the earth's temperature is rising,
apparently due to the greenhouse effectthe
warming that results from the rising concentration of heat-trapping
gases, principally carbon dioxide (CO2), in the atmosphere.
This rise in CO2 concentration comes from two sources: the burning
of fossil fuels and deforestation. Each year, more than 6 billion
tons of carbon are released into the atmosphere as fossil fuels
are burned. Estimates of the net release of carbon from deforestation
vary widely, but they center on 1.5 billion tons per year.5
The release of CO2 from these two sources is simply overwhelming
nature's capacity to fix carbon dioxide. When the Industrial Revolution
began in 1760, carbon emissions from the burning of fossil fuels
were negligible. But by 1950, they had reached 1.6 billion tons
per year, a quantity that was already boosting the atmospheric CO2
level. In 2000, they totaled 6.3 billion tons. (See Figure 2-1.)
This fourfold increase since 1950 is at the heart of the greenhouse
effect that is warming the earth.6
The carbon emissions of individual fossil fuels vary. Coal burning
releases more carbon per unit of energy produced than oil does,
and oil more than natural gas. The global fleet of 532 million gasoline-burning
automobiles, combined with thousands of coal-fired power plants,
are literally the engines driving climate change.7
In addition, in recent years the world has been losing 9 million
hectares of forest per year. Forests store easily 20 times as much
carbon per hectare as does land in crops. If the net loss of forests
can be eliminated, this source of carbon emissions will disappear.
In the northern hemisphere, the forested area is actually increasing
by 3.6 million hectares a year. The big challenge is to arrest and
reverse the deforestation in developing countries.8
At the start of the Industrial Revolution in 1760, the atmospheric
CO2 concentration was estimated at 280 parts per million (ppm).
By 2000, it had reached 370 ppm, a rise of 32 percent from pre-industrial
levels. (See Figure 2-2.) The buildup of atmospheric CO2 from 1960
to 2000 of 54 ppm far exceeded the 36 ppm rise from 1760 to 1960.9
Atmospheric CO2 levels have risen each year since annual measurements
began in 1959, making this one of the most predictable of all environmental
trends. Physics textbooks point out that as atmospheric CO2 levels
rise, so will the earth's temperature, and this is exactly what
is happening. As noted earlier, the 14 warmest years since recordkeeping
began have all come since 1980. Over the last three decades, global
average temperature has risen from 13.99 degrees Celsius in 1969-71
to 14.43 degrees in 1998-2000, a gain of 0.44 degrees Celsius (0.8
degrees Fahrenheit).10
The dramatic rise in the earth's temperature since 1980 can be clearly
seen in Figure 2-3. Not only is it rising rapidly, but it is projected
to rise even faster in the next century. If CO2 concentrations in
the atmosphere double pre-industrial levels by the end of this century,
reaching 560 ppm, the temperature is projected to rise by 1.4-5.8
degrees Celsius. Rising temperatures lead to more extreme climatic
eventsrecord
heat waves, the melting of ice, rising sea level, and more destructive
storms.11
Projected temperature rises will not be distributed evenly over
the earth's surface, but will be greater over land areas than over
the oceans and also greater in the higher latitudes than in the
equatorial regions. Inland regions in northern latitudes can expect
some of the biggest temperature jumps. A taste of what is to come
can be seen in the July 1995 heat wave in Chicago, when temperatures
reached 38-41 degrees Celsius (100-106 degrees Fahrenheit) on five
consecutive days. Although Chicago is a modern industrial city with
extensive air conditioning, this heat wave claimed more than 500
lives. And because Chicago is in the center of the U.S. Corn Belt,
the intense heat also helped shrink the 1995 U.S. corn harvest by
some 15 percent or $3 billion.12
ENDNOTES:
5. Fossil fuel-related carbon emissions figure from Seth Dunn, "Carbon
Emissions Continue Decline," in Worldwatch Institute, Vital Signs
2001 (New York: W.W. Norton & Company, 2001), p. 53; WRI estimates
emissions of 1.6 billion tons carbon per year from land use change,
most of which is related to deforestation, in WRI, op. cit. note
4, p. 101.
6. Figure 2-1 from Dunn, op. cit. note 5.
7. Carbon and fossil fuels information from Energy Information Administration,
Annual Energy Outlook 2001, with Projections to 2020 (Washington,
DC: U.S. Department of Energy, 2000), p. 48; Michael Renner, "Vehicle
Production Sets New Record," in Worldwatch Institute, op. cit. note
5, p. 68.
8. Changing forest cover from U.N. Food and Agriculture Organization
(FAO), Forest Resources Assessment (FRA) 2000, www.fao.org/forestry/fo/fra/index.jsp,
updated 10 April 2001, but see note in Chapter 8 on variations among
estimates; forests store 20 to 100 times more carbon than cleared
land, according to Mohan Wali et al., "Assessing Terrestrial Ecosystem
Sustainability: Usefulness of Regional Carbon and Nitrogen Models,"
Nature & Resources, October-December 1999, p. 27.
9. Figure 2-2 from Dunn, op. cit. note 5, pp. 52-53.
10. Hansen, op. cit. note 2; Seth Dunn, "Global Temperature Steady,"
in Worldwatch Institute, op. cit. note 5, pp. 50-51.
11. Intergovernmental Panel on Climate Change (IPCC), "Climate Change
2001: Impacts, Adaptation, and Vulnerability (Summary for Policy
Makers)" (draft Feb 2001), www.ipcc.ch/pub/wg2SPMfinal.pdf ; Figure
2-3 based on Hansen, op. cit. note 2.
12. Cindy Schreuder and Sharman Stein, "Heat's Toll Worse Than Believed,
Study Says at Least 200 More Died," Chicago Tribune, 21 September
1995; corn harvest data from U.S. Department of Agriculture (USDA),
Production, Supply, and Distribution, electronic database, Washington,
DC, updated May 2001.
Copyright
© 2001 Earth Policy Institute
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