GPHY 314 Chapter 8: Predictions of Future Climate Change

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29 Dec 2020
CHAPTER 8: Predictions of Future Climate Change
The Factors that Control Emissions
At its simplest, amount of GHG released by society is determined by total amount of goods and
services consumed by that society
GDP -> Total value of goods and services produced by an economy
o Total emissions by society are basically set by that society’s GGPD
o If GDP doubles, expect emissions to double
o More useful to break into down into product of two factors: population + affluence
As people get richer, they consume more -> Wealth effect leads to enormous
disparities in emissions per person
US emissions ~5 tons of carbon per person, China 1.7 tons per person,
Nigeria 0.1 tons per person
I = P x A x T
o I = total emissions of GHGs into atmosphere
o P = population
o A = affluence
o T = GHG intensity
o P x A = GGP
o Decomposition of emissions into these factors often referred to as IPAT relation/Kaya
o T = EI x CI
EI = energy intensity (number of joules of energy to generate one dollar of goods
and services)
Primarily determined by mix of economic activities that make up
economy, and efficiency with which economies use energy
CI = carbon intensity (amount of GHG emitted per joule of energy generated)
Reflects mix of technologies used to generate energy i.e. coal, solar,
wind, gas, nuclear
Combustion of natural gas (methane) produces least carbon dioxide per
joule among fossil fuels, so it has lowest carbon intensity which is why
it’s considered one of the “greenest” of fossil fuels
How these factors have changed in the recent past and how they will change in the future
Population increased by 80% over past few decades, today increasing by ~200,000 people per
day (growth rate approx. 1%/year)
o Affluence strongly determines how many kids a woman has, with poorest countries
having highest fertility rates
o In extremely poor societies, children can work at young age and are therefore a source of
o High rates of childhood death in poor countries means parents must have many children
o Amount of education that women receive also a factor, with fertility rates declining as
women become better educated and good-paying jobs become available
o But some events that affect population impossible to predict i.e. societal changes, chance
o Lowest population scenarios predict will peak at around 9 billion in middle of 21st C,
decreasing after and reaching 7 billion by 2100
o Higher population scenarios predict population increasing more or less continuously,
reaching 16 billion by 2100
o Best estimate that world population will stabilize during 21st C around 10 or 11 billion
Affluence measured by 80% over past few decades of 20th C
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