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The Science of Climate Change:
Explaining why we need to act NOW
Prepared with material from NPL (UK), IPCC, BOM (Aus)
Australian Institute of Physics (Vic Branch) Education Committee
Why the
urgency?
Temperature
Now
389ppm
400
2
CO Concentration (PPM)
350
300
Carbon dioxide
250
200
150
100
50
0
1700
variation in the last
few million years
1750
1800
1850
1900
1950
Australian Institute of Physics (Vic Branch)
Year Education Committee
2000
The Science of Climate Change:
Explaining why we need to act NOW
1. The Earth’s atmosphere
2.
3.
4.
5.
6.
Radiation and Greenhouse Effect
What is a Climate Model?
How has the climate already changed?
What do the models predict? Cause for concern
Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
1. The Earth’s Atmosphere
The gases in the atmosphere took some time to reach
their current proportions.
 4.5 billion years ago rock fragments orbiting the sun
formed a rocky planet.
 Volcanoes produced the first atmosphere, nearly all
water vapour and some gases including sulfur dioxide
(SO2), carbon dioxide (CO2) and ammonia (NH3).
 The water condensed to form the oceans.
 Early aquatic life produced oxygen.
 Oxygen enabled more complex life forms to evolve
about 500 million years ago.
Australian Institute of Physics (Vic Branch) Education Committee
1. The Earth’s Atmosphere
In the last 500 million years the composition of the
atmosphere has been largely unchanged, but the climate
has swung between ‘Hothouse Earth’ and ‘Snowball
Earth.
Australian Institute of Physics (Vic Branch) Education Committee
1. The Earth’s Atmosphere
Causes of Climate Changes
 Variations in Earth’s orbit
 Changes in greenhouse gases
 Movement of continents
 Uplift of Tibetan plateau
 Variation in Sun’s output
 Volcanoes
Australian Institute of Physics (Vic Branch) Education Committee
The Science of Climate Change
Australian Institute
of Physics
(Vic Branch)
Education
Committee
Australian
Institute
of Physics
(Vic
branch) Education Committee
Bubbles in Antarctic Ice
Maximum Value
300 ppm
400
350
CO2 (ppmv)
300
250
200
150
100
50
0
400
Minimum Value
180 ppm
350
300
250
200
Ice Ages
150
100
Thousands of years before the present
Australian Institute of Physics (Vic Branch) Education Committee
50
0
Carbon Dioxide in
the atmosphere
Current value
389 ppm
400
2
CO Concentration (PPM)
350
300
250
200
150
100
50
0
1700
variation in the last
few million years
1750
1800
1850
1900
Year
Australian Institute of Physics (Vic Branch) Education Committee
1950
2000
The Science of Climate Change:
Explaining why we need to act NOW
1. The Earth’s atmosphere
2. Radiation and Greenhouse Effect
3.
4.
5.
6.
What is a Climate Model?
How has the climate already changed?
What do the models predict? Cause for concern
Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
Electromagnetic Radiation
It is radiation from the Sun that is our ultimate energy source, it underpins life on the planet.
This radiation comes
in many forms.
They differ from each
other in the same way
as the signals from
radio stations differ.
They differ only in the
frequency, and because
they are all waves, also
in their wavelength.
Australian Institute of Physics (Vic Branch) Education Committee
Electromagnetic radiation from a hot body
How does an object get hot when placed in front of a fire?
Australian Institute of Physics (Vic Branch) Education Committee
Electromagnetic radiation from a hot body
This radiation is called Blackbody radiation,
because it has nothing to do with the inherent colour of the object.
Hot objects give out much more radiation than warm objects,
Hotter objects give out shorter wavelengths.
Australian Institute of Physics (Vic Branch) Education Committee
Electromagnetic Radiation
The atmosphere absorbs some forms, scatters others and allows others to pass through.
UV is absorbed by Ozone in the upper atmosphere.
Blue light is scattered more than red, making the sky blue.
Some infra red is absorbed by water and CO2.
Australian Institute of Physics (Vic Branch) Education Committee
Radiation
The Earth also emits radiation,
but the Earth is much cooler and dimmer.
The earth
radiates in
the longer
wavelengths of
infrared,
and with
much less
intensity.
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Light from the Sun heats the Earth…
Light from
the Sun
Earth
The Earth then radiates the heat away…
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
heat input from
the Sun
heat lost from the
Earth by radiation
When there is balance, the Earth’s average temperature
will be stable
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Light from the Sun heats the Earth…
•At the top of the atmosphere
•Above the Equator
•At midday
•About 1360 W/m2
Australian Institute of Physics (Vic Branch) Education Committee
Earth
What determines the Earth’s surface temperature?
Light from the Sun heats the Earth…
Earth
680
North Pole
1360 W/m2
Equator
Whole Earth Average 340 W/m2
Australian Institute of Physics (Vic Branch) Education Committee
South Pole
What determines the Earth’s surface temperature?
Light reflected from Earth
Average Value
100 watts per square metre
Light from the Sun
Average Value
340 watts
per square metre
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Light from the Sun heats the Earth…
Average Value
240 watts
per square metre
Average Value
240 watts per square
metre
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
How hot must the Earth be to radiate 240 W/m2 ?
Average Value
240 watts per square
metre
-18 °C
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Actual average +15 °C
surface
temperature
33 °C
Temperature
for radiation
balance
-18 °C
Australian Institute of Physics (Vic Branch) Education Committee
Greenhouse
Effect
What determines the Earth’s surface temperature?
The Earth’s surface is 33 °C warmer
than it would be if it had no atmosphere
So how does the atmosphere
warm the Earth’s surface?
Australian Institute of Physics (Vic Branch) Education Committee
Gases in the Atmosphere
O2
N2
About 100 molecules
Ar
Australian Institute of Physics (Vic Branch) Education Committee
Gases in the Atmosphere
About 1200 molecules
Water(H2O)
Australian Institute of Physics (Vic Branch) Education Committee
Gases in the Atmosphere
About 10000 molecules
Carbon dioxide (CO2)
Australian Institute of Physics (Vic Branch) Education Committee
Gases in the Atmosphere - Now
Concentration in 19th century
Added in 20th Century
Carbon dioxide (CO2)
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Nitrogen (N2), Oxygen (O2) & Argon (Ar)
• More than 99% of the atmosphere
• These molecules have one or two atoms
• They block some ultra-violet light, but
• Allow infra-red and visible radiation through.
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
With an atmosphere of Nitrogen
Oxygen & Argon, what would
be the surface temperature?
Average Value
240 watts
per square metre
Average Value
240 watts per square
metre
-18 °C
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
Greenhouse warming is caused by
Water (H2O)
Carbon Dioxide (CO2)
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
What is special about H2O and CO2?
• Their molecules have three atoms,
• Their natural frequencies of vibration are in the
infra-red,
• They are the earth’s blanket for reflecting certain
infra-red frequencies back down to earth.
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
What is special about H2O and CO2?
 Their molecules vibrate or jiggle in a variety of ways.
 So, many infrared frequencies can make them move.
 All these frequencies are absorbed.
Australian Institute of Physics (Vic Branch) Education Committee
Infrared Bands absorbed by Water and CO2
Ultra Violet
Visible
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Infra Red
What determines the Earth’s surface temperature?
• Out of balance…
Average:
240 W/m2
Average:
less than 240 W/m2
Some
sent back to
Earth
Average:
240 W/m2
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
• In balance at + 15 °C…
On Average:
240 W/m2
Average:
240 W/m2
150 W/m2
sent back to
Earth
On Average:
390 W/m2
Australian Institute of Physics (Vic Branch) Education Committee
What determines the Earth’s surface temperature?
+15oC
Greenhouse
Warming
33 °C
CO2
H2O
–18oC
Australian Institute of Physics (Vic Branch) Education Committee
Amount of CO2 in the air over time
1.4 ppm per
year
400
380
2
CO (ppm)
With increasing
CO2, more
radiation is
reflected back
to earth, raising
its temperature.
360
340
320
300
1960
1970
1980 1990
Year
Australian Institute of Physics (Vic Branch) Education Committee
2000
2010
The Science of Climate Change:
Explaining why we need to act NOW
1. The Earth’s atmosphere
2. Radiation and Greenhouse Effect
3. What is a Climate Model?
4. How has the climate already changed?
5. What do the models predict? Cause for concern
6. Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
Climate models are:
 Science-based tools for studying climate variability and
change.
 They use mathematical representations of physical laws,
including Newton's laws of motion, conservation of mass
and energy, heat flow, and gas laws.
 They represent important processes in atmosphere,
ocean, land surface and ice, as well as the coupling
between them.
 There are more than twenty different models developed
independently around the world.
Australian Institute of Physics (Vic Branch) Education Committee
Climate models: Specific factors
 Energy balance
 Water cycle
 Flow of air and water
Australian Institute of Physics (Vic Branch) Education Committee
Key components/processes of the climate system
 Energy balance
–
–
–
–
–
Incoming solar radiation
Planetary movements
Cloud reflection
Aerosol/dust reflection
Surface reflection and absorption
 Water cycle
 Flow of air and water
Australian Institute of Physics (Vic Branch) Education Committee
Key components/processes of the climate system
 Energy balance
 Water cycle
–
–
–
–
–
Evaporation
Cloud formation
Precipitation
Interception by leaves and branches
Runoff
 Flow of air and water
Australian Institute of Physics (Vic Branch) Education Committee
Key components/processes of the climate system
 Energy balance
 Water cycle
 Flow of air and water
–
–
–
–
Air Pressure
Circulation of air up and around - winds
Circulation of water down and around - currents
Effect of a rotating earth
Australian Institute of Physics (Vic Branch) Education Committee
IPCC AR4 WGI FAQ1.2 Fig 1
Australian Institute of Physics (Vic Branch) Education Committee
FAQ 1.2, F
Climate Models
How do they work?
The air and the oceans are broken up into cells.
© Australian Bureau of Meteorology
Australian Institute of Physics (Vic Branch) Education Committee
Climate Models
• The equations are applied to the
cells of air and water to see how
much air/heat flows between
each pair of cells.
• This is repeated all around the
Earth.
• The models have improved by
making the cells smaller.
• They are now about 110 km
square by 1 km high.
Australian Institute of Physics (Vic Branch) Education Committee
Annual average
rainfall
Observations:
1980-99
Multi-model
average: 1980-99
Australian Institute of Physics (Vic Branch) Education Committee
What do models show?
Black: Temperature
measurements
Red:
Predictions by
models assuming
human factors such
as CO2 emissions as
well as natural ones
such as sun cycles
and volcanic
eruptions.
Australian Institute of Physics (Vic Branch) Education Committee
What do models show?
Black: Temperature
measurements
Blue: Predictions by
models assuming
only natural
factors.
WGI Fig TS.23
Australian Institute of Physics (Vic Branch) Education Committee
Observed Temperature changes
1
Temperature Anomaly (Celsius)
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
1850
1870
1890
1910
1930
1950
Year
Australian Institute of Physics (Vic Branch) Education Committee
1970
1990
2010
The Science of Climate Change:
Explaining why we need to act NOW
1. The Earth’s atmosphere
2. Radiation and Greenhouse Effect
3. What is a Climate Model?
4. How has the climate already changed?
5. What do the models predict? Cause for concern
6. Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
Germany
Australian Institute of Physics (Vic Branch) Education Committee
Muir Glacier,
Alaska
Other
observations
Photo credit:
Global Warming Art
Australian Institute of Physics (Vic Branch) Education Committee
Argentina
Australian Institute of Physics (Vic Branch) Education Committee
Climate change impacts
Greenland ice sheet
The
Greenland
summer ice
melt is getting
larger at a
worrying rate.
Australian Institute of Physics (Vic Branch) Education Committee
Human induced changes
 The Arctic Ice is melting at a much faster rate than
predicted
Australian Institute of Physics (Vic Branch) Education Committee
Impact on the oceans
CO2 is absorbed by the oceans, making them more acidic.
This weakens marine skeletons.
8.3
8.2
8.1
pH
8
7.9
7.8
10 million 1 million
years ago years ago
Time
1850 1950 2050
1900 2000 2100
A change of 0.1 in pH is a 26% change in the acidity of the water.
Australian Institute of Physics (Vic Branch) Education Committee
The Science of Climate Change:
Explaining why we need to act NOW
1.
2.
3.
4.
The Earth’s atmosphere
Radiation and Greenhouse Effect
What is a Climate Model?
How has the climate already changed?
5. What do the models predict? Cause for
concern
6. Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
Annual warming for 2080-2099
17-model average
Watterson and Arblaster (2005)
Australian Institute of Physics (Vic Branch) Education Committee
Australia
Annual
(b)
Average of the change in
temperature* by 2070
predicted by 15-models.
Summer
Autumn
Winter
Spring
*relative to 1990.
Temperature change oC
Australian Institute of Physics (Vic Branch) Education Committee
Emission scenarios
Australian Institute of Physics (Vic Branch) Education Committee
Emission scenarios
A1FI An emphasis on
Fossil-fuels
(Intensive).
A1B A Balanced
emphasis on all
energy sources.
A1T Emphasis on
non-fossil energy
sources.
Australian Institute of Physics (Vic Branch) Education Committee
Scientists say that ‘2 degrees of warming is locked in’, but that
is only the most likely outcome, …
Tipping points
0.6
Greenland ice sheet
Tibetan
glaciers
0.5
Amazon rainforest
Probability
0.4
El Nino Southern Oscillation
0.3
Thermohaline circulation
0.2
Arctic
summer
ice
0.1
West Antarctic ice sheet
0
0
1
2
3
4
5
6
Committed warming as of 2005 due to GHGs (degrees C)
Australian Institute of Physics (Vic Branch) Education Committee
7
8
What the models show: Early and late 21st C
Australian Institute of Physics (Vic Branch) Education Committee
Australian Institute of Physics (Vic Branch) Education Committee
Potentially vulnerable systems in Australia
Vulnerable
Drivers of
change
Impacts
Economy
Eastern
Australian
Alps
Reduced precipitation
& snow cover
Shortened winter season. Loss of
plant species, increased shrubs,
less herbs
Threats to built environment,
biodiversity, ski industry
viability/costs and tourism
Eastern
Queensland
Coastal impacts of sea
level rise, storm
intensity
Losses to infrastructure and
coastal amenity
Tourism implications. Infrastructure
costs and insurance risk
Kakadu
Salt water intrusions
Displacement of freshwater
wetlands with mangroves
Biodiversity and tourism
implications
Murray
Darling
Basin
Reduced river flow
Enhanced water competition for
natural flows, irrigation and
town water supplies
Higher cost of water. Loss of
agricultural production and
biodiversity
Queensland
wet tropics
Coastal impacts of sealevel rise & storm
Intensity
Species extinction, loss of coral
reefs, coastal flooding and
infrastructure damage
Tourism implications. Infrastructure
costs & insurance risk
SW Western
Australia
Drying
Water shortages, fragmentation of
ecosystems
Loss of agriculture production or
enforced changes. Loss of
biodiversity
Sub
Antarctica
islands
Warming & deglaciation
Loss of key species and rapid
changes to ecosystem assemblages
Loss of biodiversity
Australian Institute of Physics (Vic Branch) Education Committee
Who’s vulnerable to climate change?
Australian Institute of Physics (Vic Branch) Education Committee
“This is not just an
environmental problem. It is
a defence problem. It is a
problem for those who deal
with economics and
development, conflict
prevention, agriculture,
finance, housing, transport
… trade and health”.
UK Foreign Secretary, Margaret Beckett,
Australian Institute of Physics (Vic Branch) Education Committee
The Science of Climate Change:
Explaining why we need to act NOW
1.
2.
3.
4.
5.
The Earth’s atmosphere
Radiation and Greenhouse Effect
What is a Climate Model?
How has the climate already changed?
What do the models predict? Cause for concern
6. Expressing concern
Australian Institute of Physics (Vic Branch) Education Committee
Expressing concern
Political
Write and phone and fax and email and talk to your local
members (State and Federal, upper and lower house).
Advocate one or more of the following:
• A maximum global CO2 level by 2020 (2050), e.g. 350 parts per
million.
• Zero emissions by Australia by, for example, 2050
• Carbon emissions tax with a tax rebate for low income earners
• Subsidy of alternative fuels: including Geothermal, Solar
Thermal, Wind, PV, Nuclear and Biomass from a carbon
emissions tax .
• Feed in tariffs for solar panels.
Australian Institute of Physics (Vic Branch) Education Committee
Expressing concern
Personal
Possible actions that you can do include:
• Retrofit double glazing,
• Adjust temperature settings of heating and cooling,
• Put up pelmets,
• Install compact fluorescents,
• Use public transport,
• Use throw rugs,
• Install solar panels and a solar water heater.
Australian Institute of Physics (Vic Branch) Education Committee
Acknowledgements
Australian Institute of Physics (Vic Branch) Education Committee