EARTH FUTURES – LABORATORY 1: SCENARIOS OF FUTURE GREENHOUSE
GAS EMISSIONS
Future climate change is dependent on the amount of greenhouse gases that humans
produce. The emission of greenhouse gases over the next century is highly uncertain.
Consequently, social scientists develop scenarios to explore different plausible futures.
Emission scenarios are usually developed using variations of the so-called IPAT identity,
where I is the impact, P is the population, A is the affluence of the population, and T
incorporates technologic change. Obviously, many of these factors will be dependent on
the sum of the economic and social development of the diverse countries of the world – a
difficult job to predict at best. Many questions arise. Will developed countries maintain
their economic edge? Will developing countries adapt leading edge technologies? Will
population continue to explode? Consequently, the scientific community has chosen to
develop emission scenarios around a group of four “families.”
A1: A future world of very rapid economic growth, low population growth, and the
rapid introduction of new and more efficient technologies. The different regions of
the world converge reducing social and economic differences. Per capita income
becomes more uniform.
A2: A future world of self-reliance and preservation of local identities. Fertility
patterns across regions change only slowly and therefore high population growth
continues. Economic development is regionally oriented and so economic
development and technologic changes are fragmented.
B1: A world of global solutions to social, economic and environmental sustainability.
Population growth is low, and the world makes a transition away from material
production to a services and information economy with the introduction of clean
and resource-efficient technologies.
B2: A world of local solutions to social, economic, and environmental sustainability.
Population growth is moderate and there are intermediate levels of economic
development, with less rapid and more diverse modes of technologic change. There
is an emphasis on environmental protection and social equity, but it focuses on local
or regional levels.
Economists, demographers, and a host of other social scientists have used these four
families to develop plausible changes in population, Gross National Product (GNP),
primary sources of energy, cumulative CO2 emissions, land use change, and
anthropogenic (human source) emissions of a variety of greenhouse gases and aerosols.
Today about 40% of the greenhouse gas emissions are from industry, somewhat less from
buildings (heating, lights, etc), about 20% from transportation, and a small fraction from
agriculture. The amount of use by these different sectors changes with population
growth, technologic innovation and the affluence of the population.
Plausible future changes can be found in the following in the excel file given as part of
this lab.
Your task is to explore the information contained within these scenarios and to begin to
develop your portfolio of what the world may be like in your old age. I suggest that you
produce graphs to include in your portfolio and then add your interpretations. Team
work will allow you to produce many graphs quickly giving you time to debate the
meaning of the information. Here are my suggestions for a minimum set of analyses
divided into a Part A (first week) and Part B (second week).
PART 1: Explore the use of Excel in making graphs and then answer three preliminary
questions.
(1) How different are the population scenarios in A1, A2, B1 and B2?
(2) How does per capita income change as a function of population growth?
(3) Is per capita income connected to rate of emission?
PART 2: Continue to explore the relationships between technology, population,
agriculture and greenhouse gas emissions:
(4) How does the notion of “technologic change” in the four scenarios translate
into changes in the primary sources of energy? What is the earliest time in which
technologic change starts to impact CO2 emissions?
(5) Total CO2 emissions are an approximation of the radiative forcing from
increases in greenhouse gases. How do the different population, economic and
technologic scenarios influence the emissions of greenhouse gases?
(6) Methane production is closely tied to agriculture. How does population
influence land use patterns and methane emissions?
Units for the excel tables:
EJ – exajoules (1018 joules)
GtC – gigatonnes of carbon (a billion tons)
Mt – megatonnes (a million tons)
Ha - hectares
Even more scenarios can be found at http://sres.ciesin.org/ including summaries for the
different regions of the earth and variations in the A1, A2, B1 and B2 categories.