In the event ofIn the event of an attack of mutant bananas In
the event of
Slide 4
Global Warming Can we collect your facts please
Slide 5
What do we mean by Climate? What is the Climate? Its the
average weather in a particular area What is the Climate? Its the
average weather Over a period a time (30 years usually) Averages of
temperatures and rain occurrence Calculated scientifically Things
like that determine what we call the Climate Determine what the
climate of a place will be.
Slide 6
One problem Do you have any personal evidence that the global
climate is changing?
Slide 7
This Evening 1.Why is the Earths surface the temperature it is?
2.The Earths Atmosphere 3.Increasing Carbon Dioxide 4.Should we be
concerned? 5.Whats going to happen? 6.What should we do?
Slide 8
Energy Balance
Slide 9
How hot does an object get when placed in front of a fire?
Slide 10
Light from the Sun heats the Earth The Sun Earth 5400 C
Slide 11
Light from the Sun heats the Earth Drawn to Scale The Sun Earth
(drawn 100 times too big) (drawn to scale)
Slide 12
Light from the Sun heats the Earth The Earth then radiates heat
away Light from the Sun Earth
Slide 13
Energy Balance heat input from the Sun heat lost from the Earth
by radiation When there is balance, the Earths average temperature
will be stable Earth Warms Earth Cools
Slide 14
The Energy Balance of the Earth
Slide 15
Earth Warms Earth Cools Energy Balance: to scale World Energy
Production heat input from the Sun heat lost from the Earth
Slide 16
Some more details
Slide 17
How much light reaches the Earth? Earth At the top of the
atmosphere Above the Equator At midday About 1360 W/m 2
Slide 18
How much light reaches the Earth? Earth North Pole South Pole
Equator 1360 W/m 2 680 Whole Earth Average 340 W/m 2
Slide 19
How much light reaches the Earths Surface Light reflected from
Earth Average Value 100 watts per square metre Light from the Sun
Average Value 340 watts per square metre
Slide 20
Hold on a moment! What about all the heat rising up from the
Earths hot centre?
Slide 21
Earth 6400 km radius 5500 C Heat flow is less than 0.1 Watt per
square metre Temperature increases by ~20 C for each kilometre
below the Earths surface Heat flow to and from surface from the Sun
240 Watt per Square metre
Slide 22
A remarkable fact Heat flow from the centre of the Earth can be
completely ignored when considering what determines the surface
temperature of the Earth!
Slide 23
What determines the surface temperature of the Earth? Infra Red
Radiation cools the Earth Light from the Sun heats the Earth
Slide 24
Radiation Balance Light from the Sun heats the Earth Average
Value 240 watts per square metre Average Value 240 watts per square
metre
Slide 25
Radiation Balance How hot must the Earth be to radiate 240 W/m
2 ? Average Value 240 watts per square metre -18 C
Slide 26
A Question What is the average temperature of the Earth? 1
metre above the surface and averaged over: day and night, all
latitudes and longitudes. all seasons (a) 15 C (b) 5 C (c) + 5 C
(d) + 15 C
Slide 27
Summary -18 C Average Surface Temperature 33 C Temperature for
radiation balance +15 C Greenhouse Effect
Slide 28
The Earths surface is 33 C warmer than it would be if had no
atmosphere
Slide 29
This Evening 1.Why is the Earths surface the temperature it is?
2.The Earths Atmosphere 3.Increasing Carbon Dioxide 4.Should we be
concerned? 5.Whats going to happen? 6.What should we do?
Slide 30
The composition of the atmosphere? Gas% Nitrogen (N 2 )78.1
Oxygen (O 2 )20.1 Argon (Ar)0.93 Water (H 2 O)0.1 to 1 Carbon
Dioxide (CO 2 )0.035
Slide 31
Illustration of atmospheric composition About 100 molecules
O2O2 Ar N2N2
Slide 32
Illustration of atmospheric composition About 1200 molecules
Water(H 2 O)
Slide 33
Illustration of atmospheric composition About 10000 molecules
Carbon dioxide (CO 2 )
Slide 34
Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) Suppose the
atmosphere contained no carbon dioxide or water N 2, O 2 and Ar is
more than 99% of the atmosphere Molecules have one or two atoms
Natural frequency of vibration in the ultra-violet Make atmosphere
opaque to ultra-violet light Transparent to infra-red and visible
radiation
Slide 35
Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) With an
atmosphere of only 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
Slide 36
Greenhouse warming is caused by Water (H 2 O) Carbon Dioxide
(CO 2 )
Slide 37
What is special about H 2 O and CO 2 Molecules have three atoms
Natural frequencies of vibration in the infra-red They make the
atmosphere opaque to certain infra- red frequencies
Slide 38
Vibrations of CO 2 and H 2 0 Different types of molecular
jiggling occur at different frequencies Water H 2 0 Carbon dioxide
C0 2
Slide 39
Absorption demo Frequency
Slide 40
The Transparency of the Atmosphere
Slide 41
Warning! Complicated diagram !
Slide 42
Infra RedUltra VioletVisible Absorption bands
Slide 43
Infra Red Radiation cools the Earth
Slide 44
Radiation Balance in the 20 th Century On Average 240 W/m 2 On
Average 390 W/m 2 150 W/m 2 sent back to Earth Average Value 240
W/m 2 On Average + 15 C
