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The Science of Climate Change
Explaining why we need to act NOWPrepared with material from NPL (UK), IPCC, BOM (Aus)
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
What is climate change?
Climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer).1
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
• Has Climate change occurred before?
YES!
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
How do we know Climate Change has occurred before?
Australian Institute of Physics (Vic branch) Education Committee
The Foot-print of Glaciers
•Geologists wondered why large boulders occurred in landscapes were they didn’t belong•The shapes of some valleys were U shaped rather than V shape. •Striations (scratches) on rocks
The Science of Climate Change
So why do Ice Ages Occur?
The ice ages are believed to be caused by a phenomena called ‘Orbital Forcing’.
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Why are Ice Ages important in this discussion?
The ice ages are part of a cycle where the Earth warms and then cools.
Ice ages and CO2 in the atmosphere follow each other
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Ice Ages
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
0
50
100
150
200
250
300
350
400
050100150200250300350400
CO
2 (
ppm
v)
Thousands of years before the present
Ice Ages
The Science of Climate Change
How do we know about the atmosphere 100,000 years ago?
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
0
50
100
150
200
250
300
350
400
050100150200250300350400
CO
2 (
ppm
v)
Thousands of years before the present
Minimum Value
180 ppm
Maximum Value
300 ppm
The Science of Climate Change
• So if this has been happening for ages why are we worried now?
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
0
50
100
150
200
250
300
350
400
1700 1750 1800 1850 1900 1950 2000
CO
2 Concentr
ation (
PP
M)
Year
YOU ARE HERE!
Current value 389 ppm
variation in the last 400,000 years
The Science of Climate Change
So what makes CO2 so important?CO2 is a greenhouse gas
And what is a greenhouse gas?Well I’m so glad you asked!
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
The Earth’s atmosphere keeps heat in like a green house.
To understand how a green house works we need to take a step back and look at the light energy that keeps us all alive……….
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
We use the wave model to help us explain light. Different colours are produced by different wavelengths of light.
The Science of Climate Change
Not all the light that comes from the sun is in the visible spectrum.
Australian Institute of Physics (Vic branch) Education Committee
How hot does an object get hot when placed in front of a fire?
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Light from the Sun
Light reflected from EarthAverage Value
100 watts per square metre
Light from the SunAverage Value
340 watts per square metre
The Science of Climate Change
Without an atmosphere what would be the average surface temperature?
-18 °C
Average Value 240 watts per square metre
Average Value240 watts
per square metre
The Science of Climate Change
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Light from the sun heats the Earth
Light from the Sun
Earth
The Earth then radiates heat away…
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Earth’s surface temperature is determined by energy in and energy out
Heat input from the Sun
Heat lost from the Earth by radiation
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The energy in and the energy out determines the Earth’s temperature. So why is the Earth warmer than -18oC
Energy gets trapped in our atmosphere and starts to heat the surface up
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
• The Atmosphere consists of
Illustration of atmospheric composition
About 100 molecules
O2
Ar
N2
Illustration of atmospheric composition About 1200 molecules
Water(H2O)
Increase in CO2 concentration Concentration in 19th century
Carbon dioxide (CO2)
Added in 20th Century
About 10000 molecules
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
What would happen if we only had Nitrogen N2 and O2 (which represents 99%) in our atmosphere?
With an atmosphere of only Nitrogen & Oxygen, what would be the surface temperature?
-18 °C
Average Value 240 watts per square metre
Average Value240 watts
per square metre
The Science of Climate Change
-18 °C
Average Surface
Temperature
33 °CGreenhouse
EffectTemperature for
atmosphere of O2 and N2
+15 °C
The Science of Climate Change
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Although they make-up less than 1% of our atmosphere the green house gases of water, H2O and carbon dioxide CO2 are able to contribute 33oC to our surface temperature.
So how can these gases have such an effect??
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Lets look at these gases as a chemist would..Hydrogen, H2 Oxygen, O2
Greenhouse gasses:
Water H2O
Carbon Dioxide CO2
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
What is special about H2O and CO2?
• Their molecules have three atoms• Their natural frequencies of vibration are in the
infra-red
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
It is this difference which has a huge effect on how they absorb and reflect light energy.
Nitrogen, N2 and Oxygen, O2 are able to absorb high spectrum light energy like UV. They protect us from these harmful rays, but they allow visible and infrared through
Greenhouse gases like Water, H2O and Carbon Dioxide CO2 are able to absorb lower spectrum light energy like infrared.
Infra RedUltra Violet Visible
What determines the Earth’s surface temperature?
Greenhouse Warming
33 °C
Others <1 °C
CO2 2 °C
H2O 31 °C
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
So greenhouse gasses drive our planet warming which is good because we’d all be pretty cold at -18oC.
But our 15oC average depends on our greenhouse gases level remaining constant, that is our energy in and energy out stabalises
• In balance at + 15 °C…On Average
240 W/m2
On Average 240 W/m2
150 W/m2
sent back to Earth
Average Value240 W/m2
The Science of Climate Change
On Average 280 W/m2
On Average 320 W/m2
On Average 390 W/m2
Light energysent back to Earth
Light Energysent back to Earth
Light Energysent back to Earth
On Average less than 240 W/m2
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Earth’s surface temperature is determined by energy in and energy out which in turn is determined by the greenhouse effect
Heat input from the Sun
Heat lost from the Earth by radiation
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
0
50
100
150
200
250
300
350
400
1700 1750 1800 1850 1900 1950 2000
CO
2 Concentr
ation (
PP
M)
Year
variation in the last 400,000 years
YOU ARE HERE!
Current value 389 ppm
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
CO2 is a particular problem because it hangs around, unlike water that cools in the atmosphere and then precipitates as rain and snow.
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
CO2 does get used up by green plants but the amount we are pumping in is more that the amount used.
300
320
340
360
380
400
1960 1970 1980 1990 2000 2010
CO
2 (p
pm
)
Year
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
CO2 does get absorbed into the oceans but this makes them more acidic which has implications for marine life.
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Looking to the future….Scientists use mathematical models of the climate to
try to work out where this might lead. These models are extremely complicated as small
changes have flow on effects.We test the accuracy of these models by applying them
to the past and seeing if they will give results that match known data.
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
But what about reports that say the average temperature has dropped since 2000…..
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1850 1870 1890 1910 1930 1950 1970 1990 2010
Year
Tem
pera
ture
Ano
mal
y (C
elsi
us)
Observed Temperature changes
http://www.cru.uea.ac.uk/cru/climon/data/themi/g17.dat
But its not just average temperature that matters
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
What happens if the model can’t keep up with reality….
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
“ It is a matter of social justice. If we care about injustice and inequality, we must care about climate change. Climate change exacerbates existing inequalities.”
Barbara Stocking — Chief Executive, Oxfam GB, Oxford, England
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
The human cost.....
Images: Human Impact Report Climate Change, Global Humanitarian Forum ,2009Words: Kofi A. Annan, President of the Global Humanitarian Forum
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
What can you do?Join a network:http://www.envict.org.au/http://www.350.org/Join an action:http://www.newscientist.com/embedded/mg20327271900-better-world-global-green-atlas
Express you concern• Find your federal members:
http://www.aph.gov.au/• Find your state members:
http://www.parliament.vic.gov.au/default.htm
The Science of Climate Change
Australian Institute of Physics (Vic branch) Education Committee
Thanks for Listening
Science Teachers for Climate Awareness
Jane [email protected]