4.4 Climate change
The greenhouse effect is accepted scientific theory. There are certain gasses in the
atmosphere that cause the sun's heat to be trapped and allow the surface of the
planet to warm. Without it the surface of the planet would be too cold for life to exist.
To explain the images are quotes from NASA:
"Left: 1880-1889. Right: 2000-2009. These maps compare temperatures in each region
of the world to what they were from 1951 to 1980 ... Two-thirds of the warming has
occurred since 1975, at a rate of roughly 0.15 to 0.20 °C per decade”. These changes in
temperature correlate with changes in CO2 levels. CO2 is now at a record high of 400
ppm.
http://climate.nasa.gov/images/ImageLarge-61.jpg
4.4
• Essential idea: Concentrations of gases in the
atmosphere affect climates experienced at the
Earth’s surface.
4.4.U1 Carbon dioxide and water vapour are the most significant greenhouse gases.
4.4.U2 Other gases including methane and nitrogen oxides have less impact.
The Earth is kept much by gases in the atmosphere that retain heat.
These gases are referred to as greenhouses gases.
The greenhouse gases that have the largest
warming effect on the Earth are:
• carbon dioxide (below)
• water vapour (e.g. clouds)
Other gases, including methane and
nitrogen oxides, have less impact.
Nitrogen oxides are released naturally
by bacteria in some habitats and also
by agriculture and vehicle exhausts.
Greenhouse gases together make up
less than 1% of the atmosphere.
http://news.bbc.co.uk/2/shared/spl/hi/sci_nat/04/climate_change/html/greenhouse.stm
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U1 Carbon dioxide and water vapour are the most significant greenhouse gases.
4.4.U2 Other gases including methane and nitrogen oxides have less impact.
The Earth is kept much warmer by gases in the atmosphere that
retain heat. These gases are referred to as greenhouses gases.
Q – why is the surface of the Earth
warmer at night if there is cloud cover?
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U1 Carbon dioxide and water vapour are the most significant greenhouse gases.
4.4.U2 Other gases including methane and nitrogen oxides have less impact.
The Earth is kept much warmer by gases in the atmosphere that
retain heat. These gases are referred to as greenhouses gases.
Q – why is the surface of the Earth
warmer at night if there is cloud cover?
The water droplets in clouds retain
heat during the day and at night reradiate the heat back to the surface
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U1 Carbon dioxide and water vapour are the most significant greenhouse gases.
4.4.U2 Other gases including methane and nitrogen oxides have less impact.
The Earth is kept much warmer by gases in the atmosphere that
retain heat. These gases are referred to as greenhouses gases.
Q – why is the surface of the Earth
warmer at night if there is cloud cover?
The water droplets in clouds retain
heat during the day and at night reradiate the heat back to the surface
Q – why is the surface of the Earth
cooler when there is more cloud
coverage.
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U1 Carbon dioxide and water vapour are the most significant greenhouse gases.
4.4.U2 Other gases including methane and nitrogen oxides have less impact.
The Earth is kept much warmer by gases in the atmosphere that
retain heat. These gases are referred to as greenhouses gases.
Q – why is the surface of the Earth
warmer at night if there is cloud cover?
The water droplets in clouds retain
heat during the day and at night reradiate the heat back to the surface
Q – why is the surface of the Earth
cooler when there is more cloud
coverage.
The water droplets in clouds reflect a
range of different wavelengths of
*Although clouds make the surface of
radiation in both directions (including
the Earth cooler in the short term.
They do not stop the greenhouse
radiation coming inward that would
effect, it is just delayed or slowed
have been re-emitted as heat*).
down.
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U3 The impact of a gas depends on its ability to absorb long wave radiation as well as on its
concentration in the atmosphere.
impact of a greenhouse gas
Ability to absorb longwave radiation
(especially infrared/heat)
abundance in the
atmosphere
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U3 The impact of a gas depends on its ability to absorb long wave radiation as well as on its
concentration in the atmosphere.
impact of a greenhouse gas
Ability to absorb longwave radiation
(especially infrared/heat)
abundance in the
atmosphere
rate of release
persistence
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U3 The impact of a gas depends on its ability to absorb long wave radiation as well as on its
concentration in the atmosphere.
impact of a greenhouse gas
Ability to absorb longwave radiation
(especially infrared/heat)
abundance in the
atmosphere
Methane has 33 times the
effect of CO2 (but is not very
abundant)
rate of release
CO2 is very abundant
making up 400 ppm by
volume of the atmosphere
(0.04%)
persistence
Water vapour enters the
atmosphere very rapidly, but only
remains for days whereas CO2
persists for years.
http://commons.wikimedia.org/wiki/File:GoldenMedows.jpg
4.4.U4 The warmed Earth emits longer wavelength radiation (heat).
4.4.U5 Longer wave radiation is absorbed by greenhouse gases that retain the heat in the
atmosphere.
How the greenhouse effect works
Approx. 25% of
solar radiation is
absorbed by the
1
atmosphere.
Approx. 75% of solar
radiation penetrates
the atmosphere and
reaches the Earth’s
surface.
2
4 Up to 85%* of re-emitted heat is
captured by greenhouse gases in
the atmosphere.
3
The surface of the Earth absorbs shortwave solar energy and re-emits at
longer wavelengths (as heat).
*This value, though variable, is known to be
rising; very likely the result of human activities.
5
Heat passes back to the
surface of the Earth,
causing warming
http://www.sumanasinc.com/webcontent/animations/content/globalcarboncycle.html
4.4.U4 The warmed Earth emits longer wavelength radiation (heat).
4.4.U5 Longer wave radiation is absorbed by greenhouse gases that retain the heat in the
atmosphere.
How the greenhouse effect works
Approx. 25% of
solar radiation is
absorbed by the
1
atmosphere.
Approx. 75% of solar
radiation penetrates
the atmosphere and
reaches the Earth’s
surface.
2
4 Up to 85%* of re-emitted heat is
captured by greenhouse gases in
the atmosphere.
3
The surface of the Earth absorbs shortwave solar energy and re-emits at
longer wavelengths (as heat).
*This value, though variable, is known to be
rising; very likely the result of human activities.
5
Heat passes back to the
surface of the Earth,
causing warming
http://www.sumanasinc.com/webcontent/animations/content/globalcarboncycle.html
4.4.U4 The warmed Earth emits longer wavelength radiation (heat).
4.4.U5 Longer wave radiation is absorbed by greenhouse gases that retain the heat in the
atmosphere.
How the greenhouse effect works
(this diagram quantifies the effect in Watts / m2)
http://commons.wikimedia.org/wiki/File:The_green_house_effect.svg
4.4.U4 The warmed Earth emits longer wavelength radiation (heat).
4.4.U5 Longer wave radiation is absorbed by greenhouse gases that retain the heat in the
atmosphere.
How the greenhouse effect works
http://www.damocleseu.org/education/Animation_about_the_greenhouse_eff
ect_182.shtml
Use the
animations/tutorials to
improve your
understanding and find
out more.
http://www.sumanasinc.com/webcontent/animations/content/globalca
rboncycle.html
http://www.sumanasinc.com/web
content/animations/content/green
house.html
http://news.bbc.co.uk/2/shared/spl/hi/sci_nat/
04/climate_change/html/greenhouse.stm
4.4.U7 There is a correlation between rising atmospheric concentrations of carbon dioxide since the
start of the industrial revolution 200 years ago and average global temperatures.
Evidence for a correlation between atmospheric carbon dioxide (CO2)
and average global temperatures
Key points
• global temperatures
show large variations
(for various reasons)
• (despite this) there is
strong support for
correlation between
atmospheric carbon
dioxide and global
temperatures
http://oceanworld.tamu.edu/resources/oceanography-book/co2problem.htm
4.4.A2 Correlations between global temperatures and carbon dioxide concentrations on Earth.
To deduce historic carbon dioxide concentrations and
temperatures ice cores are drilled in Antarctic ice sheets
Vostock ice core (pictured) drilled at a Russian monitoring
station in East Antarctica is an example of an ice core.
A cylinder of ice was collected by drilling to the
bottom of the Antarctic ice sheet. The total
length of the core was 2083 meters.
The core shows annual layers, which can be used
to date the air bubbles trapped in the ice.
Analysis of the gas content of the
bubbles gives both the
concentration of carbon dioxide in
the atmosphere and the air
temperature (from oxygen isotopes)
at the time ice was formed.
http://commons.wikimedia.org/wiki/File:GISP2_1855m_ice_core_layers.png http://en.wikipedia.org/wiki/File:GISP2_team_photo_core37.jpeg
4.4.A2 Correlations between global temperatures and carbon dioxide concentrations on Earth.
Evidence for a correlation between atmospheric carbon dioxide (CO2)
and average global temperatures
Key points
• The correlation is
supported by ice core
data over the last
400,000 years
• Temperature shows
greater variation than
CO2
• Most, but not all rises
and falls in CO2 have
correlated with
temperature rises and
falls
• The same trend has
been found in other ice
cores.
n.b. Vostock is a Russian monitoring station in East Antarctica
http://oceanworld.tamu.edu/resources/oceanography-book/co2problem.htm
4.4.A2 Correlations between global temperatures and carbon dioxide concentrations on Earth.
Evidence for a correlation between atmospheric carbon dioxide (CO2)
and average global temperatures
Key points
• The correlation is
supported by ice core
data over the last
400,000 years
• Temperature shows
greater variation than
CO2
• Most, but not all rises
and falls in CO2 have
correlated with
temperature rises and
falls
• The same trend has
been found in other ice
cores.
n.b. Vostock is a Russian monitoring station in East Antarctica
http://oceanworld.tamu.edu/resources/oceanography-book/co2problem.htm
4.4.U8 Recent increases in atmospheric carbon dioxide are largely due to increases in the
combustion of fossilized organic matter.
The link between human emissions and atmospheric levels of CO2
Key points
• There is a strong correlation
between human emissions
and atmospheric levels of
CO2
• As atmospheric CO2 levels
have increased, the amount
of CO2 absorbed by carbon
sinks has increased (only
about 40% of emissions
have remained in the
atmosphere)
Industrial revolution
has started
Large increases in
usage of fossil fuels
http://radioviceonline.com/wp-content/uploads/2009/11/knorr2009_co2_sequestration.pdf
4.4.U6 Global temperatures and climate patterns are influenced by concentrations of greenhouse
gases.
Global average temperatures are not directly
proportional to greenhouse gas concentrations.
Other factors, e.g. sun spot
activity, have an impact global
average temperatures
increases in greenhouse gas concentrations will likely cause:
• higher global average temperatures
• more frequent and intense heat waves
• some areas becoming more prone to droughts
• some areas more prone to intense periods of rainfall and flooding
• tropical storms to be more frequent and more powerful
• Changes to ocean currents, e.g. weakening of the Gulf Stream would
mean colder temperatures in north-west Europe
http://commons.wikimedia.org/wiki/File:Hurricane_Elena.jpg
4.4.A1 Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
Ocean acidification – the causes and effects
Research indicates that, by 2100 coral reefs
may erode faster than they can be rebuilt. This
could compromise the viability of these
ecosystems and the (estimated) one million
species that depend on coral reef habitat.
http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3
F
http://youtu.be/5cqCvcX7buo
http://www.sumanasinc.com/webcontent/anim
ations/content/acidification.html
http://youtu.be/GL7qJYKzcsk
http://youtu.be/Wo-bHt1bOsw
4.4.A1 Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
Ocean acidification – the causes and effects
The ocean absorbs about 25% of
the CO2 emitted into the
atmosphere. Therefore as
atmospheric CO2 increases so do
the levels in the ocean.
Since 1800 the pH of seawater* has
fallen by 0.1 pH units. Since the pH
scale is logarithmic, this represents
approx. a 30% increase in acidity.
Estimates of future CO2 levels,
indicate that by 2100 seawater
could be nearly 150% more acidic (a
further decrease of 0.5 pH) to a
level not seen for more than 20
million years.
*seawater refers to the surface of oceans which are affected more than the depths.
http://pmel.noaa.gov/co2/files/hitimeseries2.jpg
4.4.A1 Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
Ocean acidification – the causes and effects
When CO2 dissolves in water it
forms a variety of molecules:
• dissolved free CO2
• carbonic acid (H2CO3)
• bicarbonate (HCO−3)
• carbonate (CO32−)
It is not just the creation of carbonic acid that
affects pH; when bicarbonate and carbonate
ions are formed H+ ions are released thus
decreasing the pH of seawater
Carbonate ions are not very soluble, therefore the concentration in seawater is low.
Dissolved CO2 decreases the carbonate concentration further.
http://www.pmel.noaa.gov/co2/files/oareaction_med.jpg
4.4.A1 Threats to coral reefs from increasing concentrations of dissolved carbon dioxide.
Ocean acidification – the causes and effects
At risk
Benefit
Marine calcifying species, including oysters,
clams, sea urchins, shallow water corals,
deep sea corals, and calcareous plankton.*
Photosynthetic algae and sea grasses
Need to absorb carbonate ions from
seawater to make the calcium carbonate in
their skeletons.
Low CO2 is a limiting factor for
photosynthesis
The pteropod is a tiny sea creature about the size of a small pea. Pteropods are a major food source for
many animals including North Pacific juvenile salmon. The photos below show what happens to a
pteropod’s shell when placed in sea water with pH and carbonate levels projected for the year 2100.
*Shelled organisms are often keystone species and therefore the entire food web
may also be at risk.
http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F
• More consequences of global warming:
– Sea levels will rise as polar ice caps and glaciers melt –
flood coastal cities and wetlands (breeding grounds for
many species of bird, fish, shrimp, crabs – may become
extinct)
– Shift in global distribution of temps and rainfall – possibly
leading to disruption of agriculture
– May have profound affect on distribution of tree species
– may wipe out hardwood forests of eastern US
– May increase tropical disease-carrying organisms like
mosquitoes
• Should we act???
• The Precautionary principle:
– Says that preventative action should be taken
now to reduce carbon emissions and
greenhouse gas production before it is too
late (Better safe than sorry!)
– Those who wish to continue producing excess
greenhouse gases should prove that there are
no harmful effects before continuing
• Some people argue against measures to combat
global warming because there is no absolute
proof that the greenhouse effect is harmful
• Counter argument is that by the time there is
proof, there will have already been catastrophic
consequences to the environment
4.4.A3 Evaluating claims that human activities are not causing climate change.
Many claims that human activities are
not causing climate change have been
made in the media, whether it be in
newspapers, on television or on the
internet.
It is important to realize that not all
sources are trustworthy and it is
important to know the motivation of
those publishing claims on either side of
the debate.
Last Week Tonight with John Oliver: Climate
Change Debate
http://youtu.be/cjuGCJJUGsg
http://www.skepticalscience.com/
• Other ways humans are impacting ecosystems:
– Biological magnification: process by which toxic
substances accumulate in increasingly high
concentrations in progressively higher trophic
levels – ex. DDT
– DDT was one of the first
pesticides and was
thought to be harmless.
However:
– DDT is harmful because:
• Decomposers cannot
readily break it down into
harmless substances (not
biodegradable)
• It is fat soluble (not water
soluble) and tends to
accumulate in the fatty
tissues of animals
– Because of inefficient energy transfer between trophic
levels, herbivores eat large quantities of plant material,
carnivores eat larger amounts of herbivores, etc.
leading to biological magnification
– Higher trophic levels (top carnivores)have highest
concentrations in their tissues
– DDT continues to accumulate in predator’s body
throughout it’s life
Pollution
Magnification of
DDT Concentration
Pollution
Magnification of
DDT Concentration
Pollution
Magnification of
DDT Concentration
Pollution
Magnification of
DDT Concentration
Pollution
Magnification of
DDT Concentration
Pollution
Magnification of
DDT Concentration
• The widespread use of DDT threatened
populations of many animals—especially fisheating birds like the bald eagle—with extinction.
• Their eggs were so fragile they did not survive.
• By the early 1970s, DDT was banned in the U.S.
and in most other industrialized countries; as a
result, affected bird populations have
recovered.
–Acid rain
• As humans have moved toward using fossil fuels
for energy, acid rain has become a major global
issue (in addition to global warming)
• The US discharges 30 million tons of sulfur dioxide
into the atmosphere each year
– 90% of sulfur dioxide in atmosphere comes from
human industrial activities
– Nitrogen oxide is also released from vehicles, power
plants and industry
• Sulfur dioxide and nitrogen oxide combines with
water vapor in the atmosphere to form sulfuric
acid and nitric acid
• Acid often falls hundreds or thousands of miles
away (pollutants carried by the wind) dissolved in
rain (snow, fog) or as microscopic dry particles
http://www.dec.ny.gov/chemical/8418.html
• Acid eats away statues, buildings, damages trees
and crops, kills life in lakes
• Lakes become too acid to support life
• Acid rain washes away essential nutrients and kills
microbes that recycle nutrients
• Toxic metals (aluminum, lead, mercury, cadmium)
dissolve easier in acid rain and run into lakes and
streams – accumulates in fish leading to biological
magnification