For more information
on changes in atmospheric concentrations of carbon dioxide, visit: EPA
Global Warming Site: Atmospheric Change
Sensing: Carbon Dioxide
Carbon dioxide (CO2) is a greenhouse gas. It plays a key role in Earth's climate. For this reason, research on
often closely linked with research on climate change.
One group that monitors climate change is the
Intergovernmental Panel on Climate Change
. This organization was established in 1988. It is made up of members from
the World Meteorological Organization (WMO) and the United Nations Environment Programme
(UNEP). The Panel itself does not carry out research on climate change or monitor climate data. Instead,
it examines scientific, technical, and social/economic information about the topic provided by other
scientists. The Panel then determines the risk of climate change that may result from human activities.
One such risk comes from the production of large amounts of CO2.
Currently, 7.4 gigatons
emitted to the
atmosphere each year. The resulting concentration of atmospheric CO2
parts per million (ppm). This is about 85 ppm greater than the
concentration of atmospheric CO2 before the Industrial Revolution
in the early 18th century. The
Industrial Revolution began in England around 1733. This is the period of history when many new
machines were invented and factories were created. The large increase in atmospheric
CO2 since the
Industrial Revolution began is most likely the result of the demands of a larger, more industrialized human
Increases in the world population have resulted in greater energy demands for daily activities. Economic
growth has resulted in increased business and industrial energy requirements. Because the cost of "clean"
nuclear power is high, many people choose to use fossil fuels such as coal and oil as energy sources.
These energy sources are cheaper than nuclear power, but they produce a lot of
The IPCC has developed several sets of scenarios to predict changes in atmospheric
These scenarios are based on many factors, including the world population, the economy, and the cost of
One IPCC scenario for CO2 emissions over the next 100 years assumes that the human population will
only increase by 4 million people. The world's economy will grow by 2.0% per year for the next 25 years,
then growth will slow. It also assumes the cost of nuclear power will go down by 0.4% per year. This
scenario is the most optimistic. If the assumptions of this scenario are met,
CO2 emissions will increase by
1.4 GT in the next twenty-five years. Then CO2 emissions would decrease by 4.2 GT over the following
seventy-five years. The emissions of CO2 in the year 2100 will be 4.6 GT. That is 2.8 GT lower than
they are today. Although the emissions of CO2 in the year 2100 may be lower than they are today, the
actual concentration of CO2 in the atmosphere will be higher. This is because once
CO2 is emitted to the
atmosphere, it stays there for a long time. Under this IPCC scenario, the concentration of atmospheric
CO2 in the year 2100 will be 450 ppm.
The most pessimistic IPCC scenario for CO2 emissions over the next 100 years assumes the human
population will increase by 5.3 billion people. The world's economy will grow by 3.0% per year. It also
assumes the cost of nuclear power will increase. Under these conditions,
CO2 emissions will increase by
7.7 GT in the next twenty-five years, and by another 20.7 GT over the following seventy-five years.
Based on these assumptions, the predicted CO2 emissions in the year 2100 will be 35.8 GT. That is
nearly five times greater than emissions are today. The concentration of atmospheric
CO2 will be 900
The most likely IPCC scenario for future CO2 emissions lies between these two extremes. This middle
scenario is called scenario "A" or the "business as usual" scenario. It is called the "business as usual"
scenario because it assumes that population and economic growth rates, as well as nuclear energy costs,
will not change significantly in the future. Based on the assumptions of scenario A, annual emissions of
CO2 will rise to 20.3 GT by the year 2100. The concentration of atmospheric
CO2 will be 700 ppm. This
is double today's concentration.
All of IPCC's scenarios suggest that concentrations of atmospheric CO2
will increase in the next century.
The question is by how much. The answer appears to lie in the expansion of human activities. Will the
population grow? Will industry grow? Will cleaner energy sources such as nuclear power become more
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