In recent decades there have been significant increases in the average global temperature. Scientists have become concerned about the potential problems associated with global warming. It is necessary to explore the various components of global warming: why does global warming occur? While some scientists equate the increasing temperatures with normal fluctuating patterns as seen throughout history, many scientists blame global warming on the "greenhouse effect"- an increase in the average global temperature as a result of the accumulation of manmade gases in the atmosphere.
Potential consequences of global warming are changes in land conditions,
changes in weather patterns, and a rise in the sea level. Governments around
the world are uniting in efforts to control the emissions of carbon dioxide
and other greenhouse gases; at the UN Conference on Environment and Development
in Rio de Janeiro in 1992, member countries signed contracts designed to
limit emissions of such gases. Among participating countries there was a
general consensus regarding the nature of greenhouse gases: significant
global warming will continue if countries do not limit their emissions of
greenhouse gases. By emissions of greenhouse gases, scientists are mostly
referring to the burning of fossil fuels. There are many different possibilities
for controlling emissions of greenhouse gases, but these scientific debates
are beyond the scope of the paper. The specific effects of global warming
are highly debatable; in the remainder of this paper, I will discuss how
population growth relates to certain environmental problems. The meat of
this paper will draw on three separate articles, three different perspectives
on the global warming debate.
In "Population Growth and Global Warming" (1992), John Bongaarts
identifies a simple "chain of causation" to characterize the nature
of global warming, and its future implications. Human production and consumption
activities lead to the emission of greenhouse gases; hence, there is an
increasing concentration of greenhouse gases in the atmosphere. The ultimate
result of this chain is global warming. Of course, there are extremely complex
functions and models that more clearly define the various steps in the chain
of causation, but this paper will focus on those factors associated with
population growth. One detail worth noting is that "annual emission
rates of carbon dioxide are expected to approximately double by the year
2025 and then double again by the year 2100." This influx of gases
certainly will boost the average global temperature significantly in the
next century: how much the temperature will rise is unclear, but somewhere
near 4°C, according to previous projections. So, what exactly are the
determinants of greenhouse gas emission rates? Bongaart identifies six factors
that contribute to emission rates: population size, gross domestic product
per capita, energy intensity of GDP, carbon intensity of energy consumption,
and tropical deforestation. As the population grows, obviously the demand
for energy increases; hence, population is an important determining factor
of the concentration of greenhouse gases in the atmosphere. Discounting
any possibilities of intervention, scientists predict that population size
will increase (1986 to 2100) from 3.6 to 9.0 billion in the developing countries
and from 1.2 to 1.5 billion in developed countries. Coupled with economic
development (a rise in GDP per capita), population growth will stimulate
the growth of emission rates.
There are many possible ways of controlling greenhouse gas emission rates,
but the most feasible option revolves around stabilizing future CO2 emissions.
But Bongaarts insists that the "effectiveness of any such policy would
of course depend on the level and timing of stabilization and on the degree
of participation of different countries." Of course, the process of
stabilization will much more difficult to execute in less developed countries
than in the more developed world. With lower education levels, less technology
and weaker organization among their leaders, less developed countries will
require assistance from more developed countries in order to achieve desired
emission levels. Global conferences and agreements regarding population
control and fossil fuel emissions will help to facilitate this stabilization
process. Bongaarts stresses that stabilization in developing countries will
be especially difficult, because efforts to limit emissions will contradict
efforts to stimulate economic growth; less developed countries will have
to sacrifice much more than developed countries. Although population is
not necessarily the most important determinant of harmful emissions, it
is extremely important to continue to implement population control policies
in order to reduce future global warming. Hence, the global community must
incorporate such "population policies" with supplemental measures
that help to control other determinants of emissions, of global warming.
All of the models regarding global warming and population are complicated,
and they are based on various projections of economic conditions and population
trends. How exactly do economists and scientists generate these projections?
In "World Population, Economic 1, and Energy Demand, 1990-2100"
(1995), Bernard Gilland evaluates the process by which the UN and World
Energy Council (WEC) determine projections of world population, economic
growth, energy consumption and CO2 emissions. These predictions serve as
the basis for policies implemented in the global community, regarding the
control of global warming and other potential problems of the future. In
order to generate these projections successfully, the various global organizations
have to place countries in various groupings: namely, less developed versus
more developed countries. These classifications are ambiguous, depending
on how the organizations make their distinctions among different countries.
For example, the UN has a broad classification, designating a small list
of more developed countries, and labeling the rest of the nations as less
developed countries. The more developed countries include the United States,
Europe, Commonwealth of Independent States, Canada, Japan, New Zealand and
Australia. The WEC alternatively has generated two classifications. The
first category places countries in three separate groupings: Developing
countries, Central and Eastern Europe and CIS, and the Organization for
Economic Cooperation and Development (OECD). The WEC secondary classification
applies to countries' location, grouping various countries together that
comprise distinctive regions of the world. While the further details of
UN and WEC classifications are not necessarily relevant to the topic of
this paper, it is important to realize that there are different ways of
characterizing and interpreting an individual country's relative status.
Of course it is difficult to determine which classification most appropriately
categorizes various countries, given their economic, demographic and political
characteristics. Given the different classifications, there are some ambiguous
projections for population, economic growth, energy consumption and CO2
emissions. Often the organizations project low, medium and high projections,
in order to account for ambiguity and uncertainty. Gilland provides a summary
of the different methods of calculating the individual figures-of course
there are subcategories for each of the general economic and demographic
indicators. For example there many different forms of energy, and they each
have much different effects on the environment; each source merits an individual
projection. In the end, it is very difficult to determine which set of results
best predicts the future economic and demographic levels. Some projections
more plausible than others, scientists, economists and politicians can use
such figures as a rough guide for policies.
These projections are useful in assessments of and responses to environmental
problems, such as global warming. In "Population, Households, and CO2
Emissions" (1995), Landis MacKeller et al explore different ways of
defining and assessing environmental impacts. There are two general equations
that express the factors contributing to environmental impacts:
I = PAT (I = environmental impact, P = population, A = affluence, and T=
technical efficiency)
I = HAT (I = environmental impact, H = households, A = affluence, and T
= technical efficiency)
The important distinction between the equations is use of households (H)
in the second equation, as opposed to population (P) in the first equation.
MacKeller et al are especially interested in the household as a demographic
unit, more specifically in patterns of household structure in the last half-century.
In other words, perhaps the household is a better starting point for studying
changes in consumption of energy throughout the world; of course, households
in different countries have much different dynamics, given various cultural
and economic identities. Using the I = PAT identity, about one-third of
the growth of energy consumptions was a byproduct of demographic change;
whereas, using the I = HAT identity, about "three-quarters of the rate
of growth of energy consumption is accounted for by demographic increase
as measured by the rate of growth of the number of households."
From 1950 to 1990, average household sizes in developed countries decreased
significantly. [These changes are much more modest in developing countries.]
According to MacKeller et al, "this was due more-or-less equally to
changes in population age structure (mostly aging) and to increases in age-specific
household headship rates." Children were beginning to move away from
home earlier than in past years, and the aged population was living more
independently. Hence, accompanying this decrease in the size of households
was an increase in the numbers of households. Of course, there are many
reasons behind these changes in the structure household: both economic and
psychological factors. A chief marker of these changes is "modernization,"
which has changed the individual's role in the household, as well as in
society.
So, how will such changes in households and fertility rates apply to environmental
problems? The implications are ambiguous. While the decrease in fertility
rates potentially will cause a decrease in future energy consumption, the
aging population will translate to more households. More households will
increase energy demands. It is clear in this example that both impact identities
(I = PAT and I = HAT) have their shortcomings as expressions of environmental
stress. However, MacKeller et al have demonstrated how important it is to
consider different demographic units when trying to determine factors that
contribute to environmental problems, namely global warming. In the future,
"the proportion of the population aged under 15 is expected to decline
and the proportion of the population aged over 60 is expected to rise."
Furthermore, the number of households will continue to grow rapidly; the
household growth rate will exceed the individual growth rate. MacKeller
et al highlighted some important considerations about population growth
and environmental problems. Population can mean three different things:
individual, household, and community.
As we can see, environmental problems are extremely complicated, as it is
difficult to determine their causes and as well as their effects. Furthermore,
it is difficult to come up with solutions to these problems, given their
ambiguous nature. Certainly, global warming will continue to threat the
natural environment, and it is in the best interest of the global community
to consider specific measures to control this environmental problem. This
paper focused primarily on population growth as a large factor of global
warming. It is important to realize that there are many other important
factors that contribute to global warming, and that population as a demographic
unit is ambiguous. Certainly scientists and economists will have to continue
researching and analyzing environmental, demographic and economic conditions
around the world. They have demonstrated much progress in the last fifty
years but will need to continue exploring new perspectives on environmental
impacts. The best policies in the future will incorporate measures monitoring
as many of the factors contributing to global warming as possible: greenhouse
gas emissions, population growth, and GDP per capita to new a few.
John Bongaarts, "Population Growth and Global Warming" in Population
and Development Review, Vol. 18, No. 2, June 1992, pp. 299-319.
Bernard Gilland, "World Population, Economic Growth and Energy Demand,
1900-2100" in Population and Development Review, Vol. 21, No. 3, September
1995, pp. 507-540.
MacKellar, F. Landis, W. Lutz, C. Prinz and A. Goujon, "Population
and Households, and CO2 Emissions", Population and Development Review,
Vol. 21, 1995, pp. 849-865.