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Transcript
Changing Climate
Changing Understanding
… a drama in six acts
Peter Mahaffy
Brian Martin
Alberta Environment
December 8, 2010

‘An understanding of chemistry is essential as
the basis for medicine and public health, in
addressing challenges such as global climate
change, in providing sustainable sources of
clean water, food and energy, and in
maintaining a wholesome environment for the
well-being of all people.
UN International Year of Chemistry (2011)
Visualizing and Understanding
the Science of Climate Change
IUPAC Project 2008-043-1-050
The Prologue…
Act One – Carbon Today
International Geophysical Year
1957
Scripps Institute of Oceanography
http://rammb.cira.colostate.edu/dev/hillger/IGY.htm
C02 (ppm)
Perhaps one of the most
important graphs in history!
Date
Where are you? Your grandchildren?
IGY 1957
IYC 2011
CDIAC, 2010
Go to NASA/Oak Ridge Video
Act Two – View From “Deep”
History
History shows quite clearly that climate
change is natural and inevitable – there
is nothing different about our current
observed change is there? – Doesn’t this
show that it is mostly “natural”?
IPCC 2007, Climate Change: The Physical Science Basis, Working Group 1,
4th Assessment Report
I don’t get it! We weren't around
100 000 years ago but there was
clearly big climate change
happening then – again isn’t this
arguing that’s it’s natural?
Act Three – Carbon Dioxide and How
to Live a Balanced Life
Learning to see our planet
in new ways
NASA radiometer images
Wavelength Distribution of Solar Radiation
C. Middlecamp et. al, Chemistry in Context, McGraw Hill
Not to scale - IR intensity is MUCH less than visible!
Greenhouse gases – A New Idea?

1827: Fourier – theorized that greenhouse

1896: Arrhenius - proposed that changes in


gases warm the planet
atmospheric CO2 concentrations due to volcanic eruptions
and the combustion of coal can cause climate change
1938: Callendar – first noted that human emissions of
CO2 may add significantly to natural concentrations in the
atmosphere
1957: Revelle et al. – first warned that human
emissions have started a global scale geophysical
experiment and initiated an atmospheric CO2 concentration
monitoring program
Environment Canada
Radiation balance
How can greenhouse gases heat
the atmosphere?
But isn’t the absorption of CO2
saturated in the atmosphere? How
can increasing the CO2 concentration
affect temperature? Besides – isn’t
water vapour more important
anyway?
How significant are small changes in
Earth’s radiation balance?
Act Four – Spectral Windows,
Methane Clathrate Hydrates and
Other Sleeping Giants
Key Players - A Closer Look
Carbon Dioxide
Methane
Nitrous Oxide
CFCs and HCFCs
Water !
Solar activity
Aerosols
CO2, CH4, N2O – over 2000 years
Mahaffy, et. al., Chemistry: Human Activity, Chemical Reactivity, 2010, Nelson, p 86
Adapted from IPCC, 2007, 4th Assessment Report
Greenhouse Gases to Focus on?


The effect of a ‘greenhouse’ gas on climate
depends on (a) its concentration, (b) how
strongly and where in the infrared region it
absorbs energy and (c) its atmospheric
lifetime.
Global warming potential, the ability of a gas
to cause changes to earth’s climate relative
to CO2, which is arbitrarily assigned a value
of 1.
Some Key Players
Gas
Global Warming Potential
Atmospheric
Lifetime
(years)
Time Horizon
20 years
100 years
500 years
Variable
1
1
1
Methane (CH4)
12
72
25
7.6
CFC-12 (CF2Cl2)
100
11,000
10,900
5200
Nitrous Oxide (N2O)
114
289
298
153
Perfluoropropane (C3F8)
2600
6,310
8,830
12,500
Carbon dioxide (CO2)
IR Spectroscopy helps us sort out which atmospheric
gases to pay the most attention to!
Clathrates (methane hydrates)
Ken Jordan, U Pittsburgh
Methane Clathrate Hydrates:
Positive Feedback of Unknown Impact
But History may Have Some Lessons
Northern regions of Russia/Canada contain
peatland-permfrost with huge stores of methane
(CH4), 25X the GWP of CO2 over 100 years.
Courtesy of Geoff Strong
32
N2(g) + 3H2(g)
2NH3(g)
As atmospheric concentrations of
CO2 have increased by 30%, the
deposition into the atmosphere of
reactive nitrogen species has gone
up by 300%.
Human activity is now responsible
for about one-half of the entire
global cycle of nitrogen
Reactive Nitrogen Production
Nitrogen atom
efficiency
N f ertilizer
produced
N f ertilizer
applied
100
94
-6
N f ertilizer
produced
47
- 47
N f ertilizer
applied
100
94
-6
N
in crop
- 47
N
harvested
31
26
-5
- 16
N
in crop
N
in f eed
47
31
- 16
N
in f ood
14
vegetarian
diet
- 12
N
in store
7
- 24
N
consumed
N
consumed
4
-3
J. N. Galloway & E. B. Cowling, 31, Ambio, March 2002
carnivorous
diet
Terraform Mars with Super
Greenhouse Gases?
Proceedings of Natl Academy of
Sciences, Feb 2001
IPCC 2007
Act Five – Terra Less Firma and Pteropods
Our Fragile Oceans
Positive feedback loops and
arctic ice changes
Hoegh-Guldberg, O., Bruno, J. Science, 328, p 1523, 18 June 2010



The physics and chemistry of adding an acid to the
ocean are so well understood, so inexorable, that
there cannot be an iota of doubt—gigatons of acid
are lowering the pH of the world ocean, humans are
totally responsible, and the more carbon dioxide we
emit, the worse it’s going to get.
Ocean pH is lower than it’s been for 20 million years
Models predict drop from a pre-industrial pH of 8.2
to about 7.8 by the end of this century. That would
increase the surface ocean’s acidity by about 150% on
average.
Doney, S. Science, 328
18 June 2010
Predicted 2100 pH 7.8
Pre-industrial pH 8.2
Mahaffy, et. al., Chemistry: Human Activity, Chemical Reactivity,
2010, Nelson, p 552
Sea Surface pH change since
Industrial Revolution
Sea Surface CO32- change since
Industrial Revolution
Hoegh-Guldberg, O.,
Bruno, J. Science, 328, p
1523, 18 June 2010
Act Six – The Future?
http://www.gapminder.org/world/#;example=6
Fossil Fuel Emissions: Actual vs. IPCC Scenarios
10
International Energy Agency
-1
Fossil Fuel Emission (GtC y )
Carbon Dioxide Information Analysis Center
9
Averages
A1B
8
A1FI
A1T
A2
7
B1
B2
6
Full range of IPCC individual scenarios
5
1990
1995
2000
2005
2010
2015
Raupach et al. 2007, PNAS, updated; Le Quéré et al. 2009, Nature Geoscience; International Monetary Fund 2009
“What’s the use of
having developed a
science well enough
to make predictions
if, in the end, all
we’re willing to do is
stand around and
wait for them to
come true?”
F. Sherwood Roland
Nobel Laureate Chemistry
Ozone Depletion
Thank You!
Any Questions?
Mass of the Atmosphere
Basic Facts:
•Atmospheric pressure 100 kPa
•1 Pa = 1N/m2
•Radius of Earth 6.38 X 106m
Every square m of the Earth’s
surface supports 104 kg of air
SA  4 R 2
What mass of a
column of air 1m2
at the base will
exert a force of
100 kN ?
Mass  4 R 2 (104 kg / m 2 )
 4 (6.38  106 m )2 (10 4 kg / m 2 )
 5  1018 kg
Ans: mg = 100 000 N
m = 104 kg
How many molecules are there in the
atmosphere?
Basic Facts:
•Atmospheric is mostly N2 and O2
•“molar mass” approximately 30
g/mol
•Mass of atmosphere 5 X 1018 kg
Number of mols 
mass of atmosphere
molar mass
5  1021 g

 1.7  1020 mol
30 g / mol
How Much CO2 in ppm Does a Barrel
Basic Facts:
of Oil Produce?
1 barrel releases 425 kg of CO2; in moles this is
425 kg
 104 mol
0.044 kg / mol
•Carbon-based fuel releases 3.15
times its mass in CO2
•Mass of a barrel of oil is about
135 kg or
•1 barrel releases 425 kg CO2
•CO2 has a molar mass of 44g/mol
Since the atmosphere contains 1.7 X 1020 mol
one barrel will release
104
17

6

10
1.7  1020
This is the fraction of CO2 relative to the entire atmosphere – multiply by 1
million to get the parts-per-million or ppm. So, 1 barrel releases an additional
6  1011 ppm
Is the observed increase in CO2 “natural” or
Basic Facts:
…
(30  109 bbl/a)(6  1011 ppm/bbl )
 1.8 ppm/a
•1 barrel of oil releases 6 X 10-11
ppm of new CO2 into the
atmosphere
•30 billion barrels of oil are
consumed annually
Slope = 1.8 ppm/a
46 ppm
25 a
Basic Facts:
A Bit Closer to home…
what is the annual Carbon footprint of the
Alberta Oil Sands in ppm?

•Fort Mac produces 1.5 million
barrels of oil per day
•Annual Carbon footprint is 40
million tonnes of carbon dioxide
•1 barrel of oil releases 6 X 10-11
ppm of new CO2 into the
atmosphere
40 Mt CO2
 9.4  107 bbl
425 kg / bbl
(9.4  107 bbl/a)(6  1011 ppm/bbl )
 0.006 ppm/a
…but – that’s not the end of the story!
Components of Fossil Fuel Emissions
Le Quéré et al. 2009, Nature Geoscience
How about Coal-Generated Power?
Basic Facts:
•The Sundance Coal-fired Power
Generation Plant on Lake
Wabamum produces 2126 MWH
•Annual Carbon footprint is 17.5
million tonnes of carbon dioxide
The Sundance plant produces roughly 7.5/40
times as much CO2 as The Alberta Oil Sands
In other words – Sundance adds
(17.5 / 40)(0.006 ppm/a)= 0.003 ppm/a
(or about “half-a-Fort Mac”)
Let’s Re-run the Numbers…
Basic Facts:
•CO2 sources by percent:
•Coal 40%
•Oil 36%
•Natural Gas 20%
•Other 4%
If the burning of oil accounts for
only 36% of the total CO2 loading
then the total (anthropogenic)
loading is …
1.8 ppm / a
 5 ppm / a
0.36
So – where is the rest going?
How much energy do we receive from
the Sun?
Basic Facts:
•Average Solar Constant is
1.366 kW/m²
Solar constant is “spread” over the
top of atmosphere of the Earth so
each square metre receives
 R2e (1.336 kW / m2 )

4 R 2e
 334 W / m2
Thank Goodness for Greenhouse Gases!
Basic Facts:
•Earth’s albedo is about 0.35
•Solar constant So is about 1366
W/m2
• = 5.67 X 10-8 Wm-2K-4
Energy Absorbed from Sun
Esun  So (1   ) R 2e
Teff 
Energy emitted by Earth
4
EEarth  4 R 2e  Teff
4
So (1   )
4
Earth’s effective surface temperature
should be – 15 C!
Watt – Does it Matter?
At 500 ppm CO2, Earth radiates
277.702 W/m2 back into space
At the current 380 ppm CO2,
Earth radiates 279.146 W/m2
back into space
This is “only” a difference of 1.44 W/m2
Ways to see the “difference”
Basic Facts:
W/m2 over
This is 1.44
the surface of the Earth so
multiplying by the surface area of the earth gives us a
better picture:
•Surface area of Earth is 5.1 X 1014
m2
•Mass of hydrosphere is 1.4 X 1021
kg
•This represents is 7.4 X 1014 W of “extra” power that
is being absorbed by the environment
•What if you “paid” the bill – in 1 hour this would be
2.7 X 1015 kWh; @ $0.05/kWh you are on the hook
for $1.3 X 1014 or 130 trillion dollars – per hour!
•Over 1 year this difference is 2.3 X 1022 Joules of
extra energy
•In one century this could heat the oceans by U thermal  mc T
2.3  1024 J
T 
(1.4  1021 kg)(4186
 0.4 C
J
kgC o
)
How Much Will a Change in CO2 Concentration
Affect Global Temperature
Basic Facts:
•CO2 has increased from 318 ppm
to 390 ppm in the last 50 years
•Temperature increase is 0.5 C
during this time
T2 x  T
ln(2)
ln( 
o
)
First-order Temp vs ρCO2 Relationship
ln( 
T  T2 x
T2 x  (0.5 C )
o
)
ln(2)
ln(2)
 1.70 C
390
ln(
)
318
The CO2 doubling temperature is 1.70 C (low if feedback effects are
considered)
How will this affect future temperature?
If CO2 concentration grows from 390 ppm to 500 ppm:
T  1.70 C
ln(500
)
390  0.61 C
ln(2)
(This is a gross estimate – much higher in polar regions)
Contrasting “Historical” Changes
with the Change we now observe
• Go to the climate trends applet and select two different data
regions:
– Past region showing significant change
– Last 100 years of data
• Compare both Temperature and CO2 trends
Why CO2 “Saturation” is a Red
Herring…
Shortly after Arrhenius suggested that increasing CO2 could raise
atmospheric temperature, Angstrom measured the absorption in
a gas cell as a function of increasing CO2 concentration and found no significant
Increase – Conclusion – CO2 was saturated and increasing CO2
cannot block more IR.
This is wrong for a number of fundamental reasons
Some Key Points…
• The atmosphere is NOT a gas cell!
• At low concentration photons can
escape to space from lower in
the atmosphere
• As CO2 concentration increases
the optical depth increases and
photon escape occurs at higher locations in the atmosphere
• Photon “absorption” is really a process of absorption –
scattering-emission - the Equation of Transfer describes this
process
• There is never a point at which adding more CO2 does not
decrease the outward IR flux
Some Simulations using MODTRAN3
R
Animation showing CO2 absorption as concentration increases from 1 ppm
to 1000 ppm in 50 ppm steps
Graphs show outward flux at 70 km in atmosphere
A Curve of Growth…
That’s all fine BUT isn’t Water Vapour more
important anyway?
Climate Forcings – The Milankovitch
Hypothesis
• Variations in:
– Orbital eccentricity
– Obliquity
These are very large
forcings acting over
“astronomical” time
scales – ie “deep time”
These forcings produce large
changes in insolation
•Graphic depicts variation
over 500 thousand years –
250 ka in the past; 250 ka in
the future
Global average RF estimates, 2005
IPCC 2007 4th AR