Topic 8: Energy, power, climate change
8.6 Global warming
8.6.1 Describe some possible models of global
warming.
8.6.2 State what is meant by the enhanced
greenhouse effect.
Topic 8: Energy, power, climate change
8.6 Global warming
100
Describe some possible models of global warming.
The Sankey diagram
presented at the end
of Topic 8.5 The
340
greenhouse effect
75
195
30
showed that overall,
the intensity
165
entering each
520
70
interface balanced
350 40 325
precisely with the
GREENHOUSE ATMOSPHERE
intensity leaving
490
each interface.
GROUND
But if the input and output intensities are
balanced the temperature remains constant. We
show our first “model” for global warming here:
Iin – Iout = 0  ∆T = 0
1st model constraint for
temperature change
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
Our second model describes the temperature change
when Iin – Iout  0…
Recall the concept of surface heat capacity.
Cs = Q / (AT)
surface heat capacity
Cs = 4108 J K-1 m2
surface heat capacity
Recall that intensity I = P/A and P = Q/∆t. Then
Q = CsAT
(surface heat capacity)
Qin – Qout = CsAT
(net heat gain/loss)
(Pin – Pout)∆t = CsAT
(Q = P∆t)
(Pin – Pout)∆t/A = CsT
(Iin – Iout)∆t = CsT
(I = P/A)
T = (Iin – Iout)∆t/Cs
2nd model constraint for
temperature change
Note: The 1st is just a special case of the 2nd.
Topic 8: Energy, power, climate change
8.6 Global warming
110
Describe some possible models of global warming.
PRACTICE: Our equilibrium
model has been adjusted as
shown. Use the 2nd model
340
constraint to find the
75
195
30
change in temperature
over one year.
165
SOLUTION:
540
70
At the interface of
360 20 335
atmosphere and ground
GREENHOUSE ATMOSPHERE
we have:
500
GROUND
Iin = 165 + 335 = 500
Iout = 360 + 20 + 110 = 490
1 year is ∆t = 1(365)(24)(3600 s) = 3.15107 s.
Thus T = (Iin – Iout)∆t/Cs
T = (500-490)(3.15107)/(4108) = 0.79 K
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
Real global warming models are extremely complex,
simply because the earth and all of its energyexchanging and storing systems are extremely
complex. Supercomputers are used with some
success.
To gain some sort of insight into computer
modeling, consider the following simple model:
5 kg of water is added to an
aquarium once each second.
10% of the water is removed
from the aquarium once each
second.
FYI
The added water represents the
incoming energy and the removed
water is the outgoing energy.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
At first glance it might appear that the water
level will never stop increasing.
But consider the time when 5 kg is exactly 10% of
the total water in the aquarium.
From that time on, the water will be removed
exactly as fast as it is added.
Thus, at that time the “energy”
represented by the water mass
will have reached equilibrium.
FYI
The challenge is to find out
how long it takes to reach
equilibrium.
Hand calculations are tedious
but possible:
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
PRACTICE: For the water model just proposed,
complete the table:
time / s
in / kg pre-total / kg
out / kg
total/ kg
0
0
0.00
0.000
0.000
1
5
5.00
0.500
4.500
2
5
9.50
0.950
8.550
3
5
13.55
1.355
12.195
SOLUTION:
The next cell would be 8.55 + 5 = 13.55.
The next cell would be 0.10(13.55) = 1.355.
The next cell would be 13.55 – 1.355 = 12.195.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
EXAMPLE: Create a spreadsheet to determine what
the mass will be when the aquarium reaches
equilibrium and how many seconds it will take.
SOLUTION: Create a new spreadsheet with five
columns as shown here:
Highlight cell A3 and type in =A2+1 as shown.
This will increment the A cells by 1 second.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
EXAMPLE: Create a spreadsheet to determine what
the mass will be when the aquarium reaches
equilibrium and how many seconds it will take.
SOLUTION:
Highlight cell B2 and enter 5.
Highlight cell C3 and type in =B3+E2 as shown.
This will add the new input of 5 to the previous
total.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
EXAMPLE: Create a spreadsheet to determine what
the mass will be when the aquarium reaches
equilibrium and how many seconds it will take.
SOLUTION:
Highlight cell D3 and enter =0.1*C3.
Highlight cell E3 and enter =C3-D3.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
EXAMPLE: Create a spreadsheet to determine what
the mass will be when the aquarium reaches
equilibrium and how many seconds it will take.
SOLUTION:
Highlight cells
A3 through D3
all the way down
to about row 100.
Then select
EditFillDown
(or Ctrl+D) to copy
down all of the
formulas to each cell
for all 100 rows.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
water / kg
EXAMPLE: Create a spreadsheet to determine what
the mass will be when the aquarium reaches
equilibrium and how many seconds it will take.
SOLUTION:
Water Vs. Time
Finally, make a
50.0000
equilibrium
graph or read the
45.0000
spreadsheet:
40.0000
35.0000
The graph shows
30.0000
that the mass of
25.0000
water will be 45 kg
20.0000
at equilibrium.
15.0000
10.0000
This will occur
5.0000
after about 45
0.0000
seconds.
0
20
40
60
80
100
time / kg
120
Topic 8: Energy, power, climate change
8.6 Global warming
Describe some possible models of global warming.
EXAMPLE: Compare the following two images showing the
world weather for July 1, 1998:
Actual
satellite
view
60 N
30 N
0
30 S
60 S
Hadley
Centre's
computer
simulation
60 N
30 N
0
30 S
60 S
0
90E
180
90W
Note the
minor
differences
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
Global warming (and cooling) are both natural
processes and fluctuate in a periodic manner. The
four causes of global warming and cooling are:
-The sun’s varying power output.
-The Milankovitch cycles.
-Greenhouse gas fluctuation.
-Radioactivity.
We will discuss each in turn on the following
slides.
The enhanced greenhouse effect is that portion of
the greenhouse effect that is caused by humans.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The sun’s varying power output
Because the sun is
fluid rather than
solid, different
latitudes rotate at
different rates in a
process called
differential rotation.
Differential rotation
causes an 11-year
sunspot and solar
flare variation (with
changing power
output) and magnetic
pole reversal.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The sun’s varying power output
The first animation shows
sunspots during a single rotation of the sun on its axis.
The next animations show how
far-reaching solar flares are.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The sun’s varying power output
There is also a centuries-long variation in
overall power output of the sun, with the 11-year
sunspot activity superimposed:
FYI
The Maunder Minimum was a mini ice-age.
Centuries
1645 - 1715
The Maunder Minimum
11 years
Present
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The Milankovitch cycles
These extraterrestrial factors were
enumerated in 1941 by Serbian Milutin
Milankovitch in his great work on ice ages.
Factor 1: The elliptical cycle.
-In a 100,000-year long cycle the earth's
elliptical orbit changes its shape.
-Currently, our orbit is nearly circular: The
fluctuation in the solar radiation reaching us
between January and July is only 6%.
-When the orbit is at its most eccentric
fluctuation can be as great as 30%.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The Milankovitch cycles
These extraterrestrial factors were
enumerated in 1941 by Serbian Milutin
Milankovitch in his great work on ice ages.
Factor 2: The tilt cycle.
-In a 42,000-year long cycle the earth's
rotational axis tilt varies between 21.8° and
24.4° (Currently, our tilt is 22.5°).
-Tilt determines at which latitude most of the
solar radiation falls.
22.5°
21.8°
24.4°
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The Milankovitch cycles
These extraterrestrial factors were
enumerated in 1941 by Serbian Milutin
Milankovitch in his great work on ice ages.
Factor 3: The wobble cycle.
-In a 22,000-year long cycle the earth's
rotational axis wobbles like a precessing top.
Polaris
-Currently, our north pole is Vega
aimed at Polaris, the Pole Star.
-The axis can also point to Vega,
and all points in between.
FYI
When Vega marks true north the intensity of the seasons is much more extreme.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The Milankovitch cycles
These extraterrestrial factors were
enumerated in 1941 by Serbian Milutin
Milankovitch in his great work on ice ages.
Milankovitch’s work was not recognized until the
late 1960s because it was in Serbian.
In the 60s just such cycles were being discovered
in sediment and ice-core studies.
FYI
At their most extreme, Milankovitch cycles bring
an annual variation of the sun’s power of less
then 1/10th of 1 percent.
Yet this seemingly trivial variation causes
Earth’s average temperature to rise or fall by
9°F!
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
Greenhouse gas fluctuation
Both solar fluctuation and the Milankovitch
cycles are extraterrestrial sources of global
warming and cooling.
One of the two terrestrial causes are the
greenhouse gases. (The other is the earth’s
interior heat.)
Carbon dioxide, water vapor, methane, and nitrous
oxide are all greenhouse gases
which are capable of absorbing a
portion of the IR energy emitted by
the earth.
FYI
The enhanced greenhouse effect is
caused by humans increasing their levels.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
Radioactivity
The interior of the earth itself is quite hot.
The two sources of internal heat are
-radioactive minerals within the mantle, which
provides about 80-90% of Earth’s internal heat,
-and accretion remnants, which is the energy left
over from the forming of the earth through
accretion.
FYI
These effects are quite minimal
in the global warming scenario.
Recall that volcanoes only add
about 1% of the CO2 added yearly
to the atmosphere as compared to human-added CO2.
Topic 8: Energy, power, climate change
8.6 Global warming
State what is meant by the enhanced greenhouse
effect.
The controversies
Global warming is really happening.
Global warming is not really happening.
Global warming is enhanced by man.
Global warming is not enhanced by man.
Enhanced greenhouse effect is a significant
portion of the overall global warming.
Enhanced greenhouse effect is not a significant portion of the overall global warming.
Data may or may not convince one of the first
controversy but probably Earth is warming.
Given that humans produce greenhouse gases we can
probably rule out the second controversy.
Extremely complex computer simulations are
integral to deciding the third controversy, which
helps to explain its divisiveness.
Topic 8: Energy, power, climate change
8.6 Global warming
8.6.3 Identify the increased combustion of fossil
fuels as the likely major cause of the
enhanced greenhouse effect.
8.6.4 Describe evidence that links global warming
to increased levels of greenhouse gases.
8.6.5 Outline some of the mechanisms that may
increase the rate of global warming.
-Increased Greenhouse gases caused by burning
fossil fuels.
-Decreased albedo caused by melting ice caps.
Topic 8: Energy, power, climate change
8.6 Global warming
Identify the increased combustion of fossil fuels
as the likely major cause of the enhanced
greenhouse effect.
Note that deforestation accounts for only
8.1 / (29.2 + 8.1 + 8.4 + 3.7 + 0.5) = 16% of
human-caused
Breakdown of world
greenhouse gas
greenhouse gas
production.
emissions in 2004 by
Thus fossil
gas (except ozone), in
fuels produce
billion tonnes CO2
84% of our
equivalent. From IPCC,
greenhouse
2007.
emissions.
Topic 8: Energy, power, climate change
8.6 Global warming
cooling
months
warming
months
Describe evidence that links global warming to
increased levels of greenhouse gases.
The graph shows the seasonal variation of
atmospheric CO2.
Note the
seasonal
fluctuations
showing an
increase in
cooling months
and a decrease
in warming
months.
Note the
overall
increase in
CO2 levels.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe evidence that links global warming to
increased levels of greenhouse gases.
PRACTICE: Explain why
the atmospheric
concentration of CO2
increases in winter
and decreases in summer.
SOLUTION:
It’s is all about
living carbon sinks
that store CO2 in the
summer and release it
in the winter: Namelyplants and their respiration and decomposition.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe evidence that links global warming to
increased levels of greenhouse gases.
The previous data shows a steady increase in
atmospheric CO2. But how does this correlate to
average temperature? And how do we determine the
geological correlations?
The answer is ice cores.
From the concentration
of the isotopes of
hydrogen in the water we
can determine the mean
global temperature.
From the trapped air we
can determine the
Ice core sections stored
greenhouse constituents
at the National Ice Core
of the atmosphere.
Laboratory in Colorado
Topic 8: Energy, power, climate change
8.6 Global warming
Analysis of the core
has been completed
to a depth of 3350
meters, representing
about 440,000 years
of climate history.
Vostok ice core
drilling site,
Antarctica
Topic 8: Energy, power, climate change
8.6 Global warming
Topic 8: Energy, power, climate change
8.6 Global warming
Describe evidence that links global warming to
increased levels of greenhouse gases.
The graph shows the results of the Vostok ice
core analyses, representing CO2 levels and
temperatures going back 425,000 years (before
present).
Note the very strong correlation between them.
Which Milankovitch cycle seems to be driving this
variation?
100000 y
The
elliptical
variation.
Topic 8: Energy, power, climate change
8.6 Global warming
Describe evidence that links global warming to
increased levels of greenhouse gases.
The temperature and CO2 overlays show
approximately that sometimes temperature change
leads, and sometimes it follows change in CO2
levels:
So which change causes the other to change?
Topic 8: Energy, power, climate change
8.6 Global warming
Describe evidence that links global warming to
increased levels of greenhouse gases.
A more detailed plot shows perhaps that CO2
change leads temperature in change. But the
overall percentages from the previous graph gives
the lead slightly to temperature…
Topic 8: Energy, power, climate change
8.6 Global warming
Outline some of the mechanisms that may increase
the rate of global warming.
Obviously, increased need for energy leads to
increased burning of fossil fuels (or biomass)
which leads to more greenhouse gases, which would
increase the rate of global warming.
FYI
This graph
is compiled
by the
wishful
thinkers
located at
http://www.
viaazul.eu/
Topic 8: Energy, power, climate change
8.6 Global warming
Outline some of the mechanisms that may increase
the rate of global warming.
Another mechanism would be the decreased albedo
caused by melting ice caps. Ice and snow have the
highest albedo (0.6) of any terrestrial
landscape. Less light would be reflected by snow
and ice and more would be absorbed.
Anecdotal
evidence Observations of
changes in the
environment in
our lifetimes...
Topic 8: Energy, power, climate change
8.6 Global warming
Outline some of the mechanisms that may increase
the rate of global warming.
Deforestation is
also a factor. Forests
are active carbon sinks,
removing CO2 from the
atmosphere during
respiration.
Topic 8: Energy, power, climate change
8.6 Global warming
8.6.6 Define coefficient of volume expansion.
8.6.7 State that one possible effect of the
enhanced greenhouse effect is a rise in mean
sea level.
8.6.8 Outline possible reasons for a predicted
rise in mean sea level.
Topic 8: Energy, power, climate change
8.6 Global warming
Define coefficient of volume expansion.
Substances E X P A N D as they are warmed up
according to the equation
expansion due to ∆T
V = V0T
where  is the coefficient of volume expansion.
The formula shows that the change in
volume of an object is proportional
to its original volume times the
temperature change.
This formula works for both solids
and liquids.
Topic 8: Energy, power, climate change
8.6 Global warming
State that one possible effect of the enhanced
greenhouse effect is a rise in mean sea level.
As the ocean warms up its seawater expands,
taking up more volume. Thus global warming will
cause the sea level to rise.
Furthermore as Earth warms up, landlocked
glaciers will melt, adding to the
rise in sea level.
FYI
During ice ages when the land ice is
enhanced by continental-sized
glaciers, the sea level can decrease
by 100 meters!
The ice melt we are most concerned
most with, in terms of present-day
sea level rise, is glaciers and the
Antarctic ice shield.
Topic 8: Energy, power, climate change
8.6 Global warming
8.6.9 Identify climate change as an outcome of
the enhanced greenhouse effect. Done!
8.6.10 Solve problems related to the enhanced
greenhouse effect. Problems could involve
volume expansion, specific heat capacity and
latent heat.
Topic 8: Energy, power, climate change
8.6 Global warming
Solve problems related to the enhanced greenhouse
effect.
expansion due to ∆T
V = V0T
From the formula we can solve for :
 = V / V0T = (V2-V1)/V1(T2-T1).
Topic 8: Energy, power, climate change
8.6 Global warming
Solve problems related to the enhanced greenhouse
effect.
PRACTICE: The land ice sheet consists of
landlocked glaciers (in mountains) and the
Antarctic ice shield. The north polar ice sheet
is over water (floating). Explain why melting the
north polar ice shield does not
change the sea level, whereas
melting the Antarctic ice shield
does.
SOLUTION:
A floating object displaces water
equal to its weight.
Thus when floating ice becomes
water, it just fills in the space
in the ocean it already took up
and doesn’t change its depth.
Topic 8: Energy, power, climate change
8.6 Global warming
Solve problems related to the enhanced greenhouse
effect.
Topic 8: Energy, power, climate change
8.6 Global warming
8.6.11 Identify some possible solutions to reduce
the enhanced greenhouse effect.
-Increase power production efficiency.
-Replace coal and oil with natural gas.
-Use combined heating and power systems (CHP).
-Use renewable energy and nuclear power.
-Use CO2 capture and storage.
-Use hybrid vehicles.
Topic 8: Energy, power, climate change
8.6 Global warming
8.6.12 Discuss international efforts to reduce
the enhanced greenhouse effect.
-Intergovernmental panel on climate change
(IPCC),
-Kyoto Protocol,
-Asia-Pacific Partnership on Clean Development
and Climate (APPCDC).