ECON 318 Lecture 82: Econ 318_F2016_Chapter_082_The Kaya Identity
12 Nov 2016
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ECON 318: Canadian Economic Policy & Institutions 2016-2017
Notes for Lecture -- 082
THE KAYA IDENTITY
Greenhouse gases
An atmosphere (from Greek ατμός - atmos, 'vapor' + σφαίρα - sphaira, 'sphere') is a layer of gases
that may surround a material body of sufficient mass, by the gravity of the body, and are retained for
a longer duration if gravity is high and the atmosphere's temperature is low. Some planets consist mainly
of various gases, but only their outer layer is their atmosphere (see gas giants).
Earth's atmosphere, which contains oxygen used by most organisms for respiration and carbon
dioxide used by plants, algae and cyanobacteria for photosynthesis, also protects living organisms
from genetic damage by solar ultraviolet radiation. Its current composition is the product of billions of
years of biochemical modification of the paleoatmosphere by living organisms.
Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal
infrared range. This process is the fundamental cause of the greenhouse effect.
Greenhouse gases trap heat within the surface-troposphere system. This mechanism is fundamentally
different from that of an actual greenhouse, which works by isolating warm air inside the structure so that
heat is not lost by convection.
The greenhouse effect is the heating of the surface of a planet or moon due to the presence of an
atmosphere containing gases that absorb and emit infrared radiation.
What is Infrared Radiation?
The light we see with our eyes is really a very small portion of what is called the
"Electromagnetic Spectrum." The Electromagnetic Spectrum includes all types of radiation -
from the X-rays used at hospitals, to radio waves used for communication, and even the
microwaves you cook food with.
Radiation in the Electromagnetic Spectrum is often categorized by wavelength. Short
wavelength radiation is of the highest energy and can be very dangerous - Gamma, X-rays and
ultraviolet are examples of short wavelength radiation. Longer wavelength radiation is of
lower energy and is usually less harmful - examples include radio, microwaves and infrared. A
rainbow shows the optical (visible) part of the Electromagnetic Spectrum and infrared (if you
could see it) would be located just beyond the red side of the rainbow.
Although infrared radiation is not visible, humans can sense it as heat, similar to the heat
that one would experience if he put his hand next to a hot oven.
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The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on by
John Tyndall in 1858, and first reported quantitatively by Svante Arrhenius in 1896.
In the absence of the greenhouse effect and an atmosphere, the Earth's average surface temperature of 14
°C (57 °F) could be as low as −18 °C (−0.4 °F), the black body temperature of the Earth.
The main greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane,
nitrous oxide, and ozone.
The contribution to the greenhouse effect by a gas is affected by both the characteristics of the gas
and its abundance. For example, on a molecule-for-molecule basis methane is about eight times stronger
greenhouse gas than carbon dioxide, but it is present in much smaller concentrations so that its total
contribution is smaller.
When these gases are ranked by their contribution to the greenhouse effect, the most important are:
water vapor, which contributes 36–72%
carbon dioxide (CO2), which contributes 9–26%
methane (CH4), which contributes 4–9%
ozone(O3), which contributes 3–7%
Also, carbon monoxide (CO) that elevates concentrations of methane and ozone or oxidizes to carbon
dioxide, nitrous oxide (N2O) the main cause of ozone depletion, nitrogen oxyde (NOx), and sulfur dioxide
(SO2) which, in the presence of catalysts, produces acid rain.
The_green_house_effect.svg (SVG file, nominally 1,198 × 834 pixels, file size: 660 KB)
http://en.wikipedia.org/wiki/File:The_green_house_effect.svg
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The sun is ultimately responsible for virtually all energy that reaches the Earth's surface. If this were the
total heat received at the surface, then the Earth's surface would be expected to have an average
temperature of -18 °C. Instead, the Earth's atmosphere recycles heat coming from the surface, which
results in an average surface temperature of roughly +14 °C.
Of the surface heat captured by the atmosphere, more than 75% can be attributed to the action of
greenhouse gases that absorb thermal radiation emitted by the Earth's surface. The atmosphere in turn
transfers the energy it receives both into space (38%) and back to the Earth's surface (62%), where the
amount transferred in each direction depends on the thermal and density structure of the atmosphere.
This process by which energy is recycled in the atmosphere to warm the Earth's surface is known as
the greenhouse effect and is an essential piece of Earth's climate.
The mechanism is named after the effect of solar radiation passing through glass and warming a
greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing
airflow, isolating the warm air inside the structure so that heat is not lost.
Under stable conditions, the total amount of energy entering the system from solar radiation will exactly
balance the amount being radiated into space, thus allowing the Earth to maintain a constant average
temperature over time. However, recent measurements indicate that the Earth is presently absorbing
more than it emits into space. This increase, associated with global warming, is believed to have
been caused by the recent increase in greenhouse gas concentrations
Anthropogenic greenhouse effect
Anthropogenic global warming (AGW), a recent warming of the Earth's surface and lower
atmosphere is believed to be the result of an "enhanced greenhouse effect" mainly due to human-
produced increases in atmospheric greenhouse gases.
Human activities since the start of the industrial era around 1750 have increased the levels of
greenhouse gases in the atmosphere. The 2007 assessment report compiled by the IPCC noted that
"changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation
alter the energy balance of the climate system", and concluded that "increases in anthropogenic
greenhouse gas concentrations is very likely to have caused most of the increases in global average
temperatures since the mid-20th century".
Carbon dioxide is the human-produced greenhouse gas that contributes most of radiative forcing
from human activity. CO2 is produced by fossil fuel burning and other human activities such as cement
production and tropical deforestation. The current observed amount of CO2 exceeds the geological record
maxima (~300 ppm) from ice core data. The effect of combustion-produced carbon dioxide on the global
climate, a special case of the greenhouse effect first described in 1896 by Svante Arrhenius, has also been
called the Calendar effect.
The Keeling Curve
The Keeling Curve is a graph showing the variation in concentration of atmospheric carbon dioxide
since 1958. It is based on continuous measurements taken at the Mauna Loa Observatory in Hawaii under
the supervision of Charles David Keeling. Keeling's measurements showed the first significant
evidence of rapidly increasing carbon dioxide levels in the atmosphere. Many scientists credit
Keeling's graph with first bringing the world's attention to the effects that human activity were having on
the Earth's atmosphere and climate.
Document Summary
Econ 318: canadian economic policy & institutions 2016-2017. Some planets consist mainly of various gases, but only their outer layer is their atmosphere (see gas giants). Earth"s atmosphere, which contains oxygen used by most organisms for respiration and carbon dioxide used by plants, algae and cyanobacteria for photosynthesis, also protects living organisms from genetic damage by solar ultraviolet radiation. Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms. Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. Greenhouse gases trap heat within the surface-troposphere system. This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection.
