The Anthropogenic
Greenhouse Effect
Lesson 3
December 9th, 2010
History in a Tree Trunk
• Recording growth is one way to document change.
The growth of a tree is documented in the widths of
its rings.
• One tree ring is formed every year,
during the summer when the tree
grows.
• Thicker rings mean the tree grew in
better conditions; enough
precipitation and appropriate
temperatures.
• Thin rings mean poorer conditions:
drought, or higher or lower
temperatures than usual.
History in a Tree Trunk
• By comparing the rings, scientists can determine
the weather conditions over the life of the tree.
Since some trees live for hundreds of years, the
rings provide long-term climate data.
Greenhouse Gases
• The natural greenhouse effect is due mainly to the
presence in our atmosphere of water vapour, with
other naturally occurring greenhouse gases, such as
carbon dioxide, methane, and nitrous oxide, also
playing a role. However, these gases are also
produced by human activities, such as industry,
electricity generation, transportation, and agriculture.
• The four main
greenhouse gases are
water vapour, carbon
dioxide, methane, and
nitrous oxide.
Greenhouse Gases
• Persistence is the length of time the gas
remains in the atmosphere.
• Gases that persist longer can absorb thermal
energy over a longer period of time.
Persistence of carbon dioxide is not defined
because it depends on the amount emitted
and carbon dioxide has a variety of sinks
(places of storage).
• Oceans, Forests
Greenhouse Gases
Gas
Carbon Dioxide
CO2
Methane CH4
Nitrous Oxide
N2O
Global Warming
Potential over 100
years
1
Persistence
(Years)
-
25
12
298
114
History of Greenhouse
Gas Research
• The discovery that different gases
absorbed infrared radiation differently
dates back to the work of the Irish
scientist John Tyndall in 1861.
• Climatologists discovered that a good
source of data was in the continental
glacier in Greenland, a glacier that
had been there for hundreds of
thousands of years.
Greenland Ice Core
Project (GRIP)
• Each year’s snowfall is recorded as a distinct
layer. From 1989 to 1992, a 3029-m-long ice
core was drilled vertically and removed from
the continental glacier.
At its deepest, the ice layer is
thought to be 200 000 years old,
while the ice layer at the surface
was formed the previous winter.
The pieces of the ice core were
dated, labelled, and stored
frozen.
Greenland Ice Core
Project (GRIP)
• Ancient ice can be studied, air at the
time of freezing is trapped in the ice
can be analyzed for CO2
concentrations. CO2 remained stable
for 10,000 years at 280 ppm, then
around 1750 (Industrial Revolution)
CO2 began to rise rapidly to its
current state of 385 ppm.
• Ancient ice can be studied, air at the time
of freezing is trapped in the ice can be
analyzed for CO2 concentrations.
CO2 remained stable for
10,000 years at 280 ppm,
then around 1750 (Industrial
Revolution) CO2 began to rise
rapidly to its current state of
385 ppm.
Greenhouse Gas Concentrations
• During the Industrial Revolution, the focus
shifted rapidly to coal-fired steam engines
and the mass production of goods. Human
society became more and more dependent
on the consumption of fossil fuels.
Increased greenhouse gas
concentrations mean that less
thermal energy is released
back into space, and as a
result, the average
temperature at Earth’s surface
increases.
Greenhouse Gas Concentrations
• The additional greenhouse gas
emissions are causing the
anthropogenic greenhouse effect,
which is the enhancement of the
natural greenhouse effect due to
human activities.
Sources of Greenhouse Gases
• The most significant greenhouse gas is
carbon dioxide. Any process that releases
carbon dioxide to the atmosphere is called a
carbon source. Example: Burning fossil
fuels and the cellular respiration.
Sources of Greenhouse Gases
• Fossil fuels - coal, oil, and natural gas —
formed underground from the remains of
once-living organisms.
As a carbon source, very little
CO2 and CH4 is released. When
it is burned, large amounts of
CO2 and N2O are produced.
For every litter of gasoline
burned, 2.3kg of CO2 is
produced.
Greenhouse Gases
Greenhouse
Sources
Gases
Carbon
- Burning coal, oil,
dioxide CO2
gasoline, and natural gas
- Cement making
Methane CH4 - Production of petroleum
products
- Rice paddies, landfills,
cattle
Nitrous
- Burning coal, oil,
Oxide N2O
gasoline, and natural gas
- Deforestation
- Natural gas
leaks
- Coal mining
- Fertilizer
Increasing Greenhouse Gas
Emissions
• Forests play an important role in removing
carbon dioxide from the air through the
process of photosynthesis. Photosynthesis is
a carbon sink
Any process that takes
carbon dioxide from the
atmosphere and stores it.
Example: As the ocean
warms CO2 stored in the
cold water is released in the
air.
Increasing Greenhouse Gas
Emissions
• Deforestation has decreased the
size of Earth’s Carbon sink. The
amount of CO2 being added to
the atmosphere is more than
carbon sinks can remove, there
is a net increase in atmospheric
CO2.
– CO2 has increased by 38% in
the last 200 years.
Increasing Greenhouse Gas
Emissions
Greenhouse Gases, Global
Warming, and Climate Change
• Climate scientists have concluded that the
increased emissions of greenhouse gases by
human activity have influenced the global
climate.
The anthropogenic
greenhouse effect is a
change in Earth’s net
radiation budget caused by
the increase in humangenerated greenhouse
gases.
Greenhouse Gases, Global
Warming, and Climate Change
• Temperatures from 1880 to 2008 indicate
that the 8 warmest years have all occurred
since 1998.
• The warming trend is known as global
warming,
The observed increase
in Earth’s average
annual temperature.
Greenhouse Gases, Global
Warming, and Climate Change
• Global warming is leading to climate
change,
– The significant long-term change in
expected climate patterns.
• Climate change means that more than just
temperature is changing; so are the number
and severity of storms, the strength of
winds, and the amounts of precipitation,
contributing to both floods and droughts. In
general, the world is experiencing more
extreme conditions
A Global
Problem
• An important international
organization that has noted the
change is the
Intergovernmental Panel on
Climate Change (IPCC), a
group of the world’s leading
climate scientists from many
countries brought together by
the World Meteorological
Organization (WMO) and the
United Nations Environment
Program (UNEP).
A Global Problem
• The IPCC has linked global warming
to the increase in the amount of
greenhouse gases in the atmosphere.
• If we continue living like we are
now, global warming will happen
even faster.
Human Activities Contribute to
Climate Change
• Both natural processes and human
activities can affect carbon
sources, carbon sinks, and the
anthropogenic greenhouse effect.
• Example: Forest fires remove the
forest carbon sink and add carbon to
the air.
Human Activities Contribute to
Climate Change
• The generation of electricity, transportation
and industry also produces large amounts of
CO2, but lifestyle also contributes to the
greenhouse gas.
We live in a disposable society
where everything is thrown out.
Landfills compress the garbage;
bacteria break down the garbage
and produce methane gas. By
reducing consumption we can help
to reduce our carbon footprint.
Human Activities Contribute to
Climate Change
Questions
• 1. What do thicker tree rings mean? K (1)
• 2. Name three greenhouse gases and give one human activity
that produces each one. K (2)
• 3. Where do scientists find the gas samples to analyze in
ancient ice? K (1)
• 4. Define “carbon source” and “carbon sink.”Give two
examples of each. C (2)
• 5. Define the term “anthropogenic greenhouse effect.” Why is
it important to distinguish it from the term “natural greenhouse
effect”? C (2)
• 6. List three human activities that contribute to climate
change. K (1)