Transcript here - University of Warwick

Facts, Lies, Myths and Opinions about the Greenhouse Effect:
[subtitle] are we doomed, or what are we going to do?
(RSC Roadshow, Warwick University, 13.11.14)
Professor Richard Tuckett (Chemistry, University of Birmingham)
 What is the greenhouse effect? Does it cause global warming?
 Is global warming the same as climate change?
 What is the relationship between ozone depletion and the
greenhouse effect? Should politics be involved?
 What are the physical properties of a greenhouse gas that
determines its effectiveness as a compound that causes climate
change and global warming?
 Why are we obsessed with CO2 as if it is the only greenhouse gas?
Is this backed up by the scientific evidence?
What are facts, myths, opinions or even lies in this most ‘political’ of
scientific subject ?
Four myths about atmospheric science




‘The Greenhouse Effect is all bad news ; detrimental to life on earth’
‘Its all about carbon dioxide’
‘No difference between the Greenhouse effect and Ozone depletion’
‘Weather and Climate are the same phenomenon’
Two very strong statements from scientists
‘Global warming is the most serious phenomenon
affecting the world’s security and prosperity,
more so than terrorism’
(David King, UK Government Chief Science Adviser, 200007)
‘Don’t undermine the science just because you don’t
like the economics. That’s a dangerous slope because
you are not just undermining [the issue], you’re also
undermining the basis of rational decision-making
in society’ (Brian Cox, Guardian, Sept 2014)
Statements from an influential non-scientist
‘Global warming is not occurring. Even if it is, it is
unrelated to man’s activities on earth’

'I have opinions of my own, strong opinions,
but I don't always agree with them’
(George Bush, 2000-2008, 2014?)
Regions of the earth’s atmosphere
 Vacuum-UV
(l < 200 nm)
 UV
(200 < l < 390
nm)
 Visible
(390 < l < 700
nm)
90% of earth’s atmosphere in troposphere, 10% in stratosphere
99% of earth’s atmosphere is N2 or O2
Simple Photochemistry
Vacuum-UV
UV
visible
IR
100 – 200 nm
200 – 400 nm
400 – 750 nm
750 - 20000 nm
E = hn = hc / l
(E  as l )
E, energy of photon
h, Planck’s Constant
n, frequency of photon
c, velocity of light
l, wavelength of photon
200 nm : 50000 cm-1, 598 kJ mol-1; 3000 nm or 3 mm : 3333 cm-1, 40 kJ mol-1 4
For a bond to break hn > bond energy. IR absorption only causes thermal effects
Education in
Chemistry
(RSC) (2008)
45, 17-21.
Chapter 1 : R P Tuckett
The role of atmospheric gases in
global warming
August 2009
DOI : 10.1016/B978-0-444-53301-2.00001-4
ISBN : 978-0-444-53301-2
2nd edition (2015) :
The causes of enhanced
concentrations of greenhouse
gases in the atmosphere :
possible solutions?
CO2 concentrations are rising : 280 ppmv to 394 ppmv in period 1750-2014.
I ppmv (at 1 bar and 298 K) is a number density of 2.5 x 1013 molecules cm-3
Year / AD
CO2 and Temperature change over ‘recent’ years : guilty ?
Is the correlation between CO2 concentration and global T ‘proven’ ? No
…….
(i) Middle ice age [1460 AD], (ii) first years after Ind Rev [1750-1920 AD]
The infamous ‘hockey stick’ graph.
UBC Canada Environ Agency. Accuracy of data, especially in 1000-1750 AD?
Development of Antarctic Ozone Hole, 1979-1997
Clear anti-correlation of ClO· and O3 concentrations in Spring in Antarctic
J G Anderson, J. Geophys. Res., (1989) 94, 11465
RESOLUTION in the data
O3
ClO
Black-Body curves of Sun (5780 K) and Earth (290 K)
Emitted energy
Emitted energy a T4
lmax a T-1
Sun
5780K
0.1
0.5
1
peak at
~10mm
peak at
~0.5mm
Earth
290K
5
10
wavelength / mm
50
100
Energy balance : UV + Visiblein (sun) = IRout (earth)
1/ 4
Tearth
 Fs (1 - A) 
= 
 4s 
Tearth should be 256 K (-17 oC)
Absorption of IR
radiation emitted by the
Fs solar flux, s Stefan’s Constant, A Earth’s albedo
earth by gases in the
troposphere.
Radiation (ca. 38%) is trapped,
like a greenhouse. Some
reflected back to earth.
Leads to an increase in
temperature of ca. 34 K : 30 K is
due to H2O, 3 K due to CO2, 1 K
to CH4, N2O, O3. These are the
‘primary’ GH gases, all good
news. H2O the most important.
Earth’s atmosphere is
78% N2, 21% O2 ;
neither absorb IR radiation.
Satellite data confirming trapping of IR radiation (Nimbus 4)
RP Wayne, Chemistry of atmospheres (1991)
CO2
O3
H2O (+ N2O, CH4)
- - - - - spectrum expected for a black body at temperature T.
 ‘Primary’ GH gases : n2 mode of CO2 (12-16 mm), O3 (9.6 mm), H2O (< 6.3 mm)
 ‘Secondary’ GH gases : (i) pollutants that absorb IR strongly in range 6-25 mm
where CO2 and H2O do not absorb (e.g. CH4, N2O, CFCs, HFCs, PFCs).
(ii) increasing concentrations of CO2 and O3 since Industrial Revolution.
The increase in GH concentrations since ca. 1750 causes the secondary GH effect …….
Molecule
Mole Fraction
ppmv (2014)
ppmv (1748)
% increase
________________________________________________________________________________________
N2
0.78 or 78 %
780 900
780 900
0
O2
0.21 or 21 %
209 400
209 400
0
H2O
H2O
0.03 (100% humidity, 298 K)
0.01 (50% humidity, 298 K)
31 000
16 000
31 000
16 000
0
0
Ar
0.01 or 1 %
9 300
9 300
0
CO2
3.8 x 10-4 or 0.038 %
393
279
41
Ne
1.8 x 10-5 or 0.002 %
18
18
0
CH4
1.77 x 10-6 or 0.0002 %
1.80
0.72
150
N2O
3.2 x 10-7 or 0.00003 %
0.32
0.27
18
O3 (troposphere)
3.4 x 10-8 or 0.000003 %
0.036
0.025
44
All CFCs
8.7 x 10-10 or 8.7 x 10-8 %
0.0009
0

All HCFCs
1.9 x 10-10 or 1.9 x 10-8 %
0.0002
0

All PFCs
8.3 x 10-11 or 8.3 x 10-9 %
0.00008
0

All HFCs
6.1 x 10-11 or 6.1 x 10-9 %
0.00006
0

[Data from : IPCC 2013 5th Assessment Report]
Properties of greenhouse gases
(absorption of infra-red radiation into vibrational modes of the gas)
Vibration must change the dipole moment of the molecule, dm / dq ≠ 0.
N2 and O2 (99% of atmosphere) play no role. Atmosphere is very ‘fragile’.
 Molecule must absorb in the range 5-25 mm. Coincidentally, CO2 absorbs at 15
mm ; the spectroscopic properties of CO2 are being unkind to nature.
 Long lifetime in the earth’s atmosphere ; no reaction with OH and O*(1D), or
photodissociation in troposphere (300-700 nm) or stratosphere (200-300 nm).

IR spectroscopy, absolute absorption coefficients
Reaction kinetics of greenhouse gas with OH and O*(1D)
Photodissociation of greenhouse gas with UV / visible radiation (200-500 nm)
Global Warming Potential (GWP)
A molecule with a large GWP is one with strong IR absorption, long
lifetimes, and concentrations rising rapidly due to man’s activity
CO2 = 1, CH4 = 28, CF2Cl2 = 10200, SF6 = 23500 CF3SF5 = 17400
n2 mode of CO2
2.0 x 1013 vibrations per second (or 50 fs per vibn)
667 cm-1 or 15.0 mm
Infra-red active : causes all the problems
O
C
O
CO2
O3
CH4
N2O
CF2Cl2
[all CFCs]
SF6
SF5CF3
Concentration (2014)
/ ppmv
393
0.036
1.80
0.32
0.0005
[0.0009]
7.3 x 10-6
1.2 x 10-7
DConcentration
(1748 - 2014) / ppmv
114
0.011
1.08
0.05
0.0005
[0.0009]
7,3 x 10-6
1.2 x 10-7
Radiative efficiency, ao
/ W m-2 ppbv-1
1.4 × 10-5
3.3 × 10-2
4.6 × 10-4
3.4 × 10-3
0.32
[0.18 - 0.32]
0.57
Total radiative forcing
/ W m-2
1.82
0.17
[0.27]
4.1 × 10-
Contribution from
long-lived GH gases to
overall secondary
greenhouse effect / %
64
11
17
6
6
[9]
0.14
0.003
ca. 50200
ca. days
- weeks
12
121
100
[45 - 1020]
3200
800
1
-
28
265
10200
23500
17400
Greenhouse Gas
(IPCC 2013 data)
Lifetime, t / years
Global Warming Potential
(100-year projection)
ca. 0.35
0.48
0.17
[4660 -13900]
0.59
(world
record)
9.4 × 10-5
3
Ravishankara and Lovejoy, JCS Faraday Trans., (1994) 90, 2159
[written six years before the CF3SF5 story began]
‘When CFCs were invented and released into the
atmosphere, their deleterious effects were not known.
Fortunately, CFCs are relatively short-lived (ca. 100
years) compared to perfluorocarbons, CxFy (ca. 1000
years) ; it will take only about a century for CFCs to be
removed from the atmosphere once their emissions are
curtailed.
The release of any very long-lived species into the
atmosphere should be viewed with great concern. PFC
(and CF3SF5) lifetimes, though long on historical
timescales, are short compared to evolutionary
timescales. Life on Earth may not be able to adopt to
the changes these emissions may cause.’
‘Ravi’
‘Thus, it seems prudent to ask if a long-lived molecule should
be considered ‘guilty’, unless proven otherwise.’
or Don’t put a long-lived pollutant up into the atmosphere in the first
place. Attack problem at source. (Carbon trading is nonsense.)
Targets for carbon reduction
UK : Reduce GH gas emissions to less than 20% of 1990 levels
by the year 2050. Reduce CO2 emissions to less than
74% of 1990 levels by the year 2020.
EU : Reduce CO2 emissions to less than 60% of 1990 levels
by the year 2030. Produce at least 27% of energy from
renewable sources by 2030.
Enshrined in law (UK) and EU protocols, but what happens if ..
US : Less strict reduction targets, Obama is committed,
but will they survive a change in President in 2016?
China : Vague commitment that GH emissions will slow down after 2030.
India : Nothing
Africa : Nothing
Kyoto Protocol (1997) : so out of date that it is worthless
What do these numbers mean to you and me?
David MacKay : Sustainable Energy – without the hot air (2009) UIT Cambridge
(free from the internet)
Units are metric tons of CO2 emitted per person per year. Estimate of how little
CO2 we should be emitting if DT is to be limited to 2 oC by the year 2100.
Population / billion
(2014)
(2100)
----------------------------------------------------------------------------------------------Planet Earth
7.27
5.8
1.5
China
1.40
6.2
1.5
India
1.27
1.3
1.5
UK average
0.06
13.7
1.5
EU average
0.51
15.0
1.5
US average
0.32
23.0
1.5
MacKay again. Now different units of kWh energy usage per person per day
Currently, the average person in the UK uses 125 of these units
He suggests :
Approx saving
What we as individuals can do
Turn down thermostats and wear more clothes
20
Stop flying
35
Modify our means of short-distance transport
20
Become vegetarian
10
Change all lights to LED
4
Keep old gadgets such as computers
4
What we as individuals have less control over
Avoid packaging and buying clutter
20
But do not do ‘guilt’ : it is negative and not constructive
Policies cannot apply to the young, old, disabled or infirm
Concentrate on us in the UK.
(1) What would be easy to implement?
If I were Prime Minister ........
 Reduce the minimum working temperature from 16 oC to 15 oC
 Reform Sunday trading laws
 Price domestic air travel in the UK out of the market
 with Huge expansion of train travel within the UK
 with Huge expansion of safe cycling routes in the UK
 Reform 1988 Education Act so that everyone attends their local school
 Provide free double glazing and roof insulation to all domestic houses
 Reform Health & Safety legislation : is packaging on everything needed?
(2) What would be moderately difficult to implement?
if we are serious
... But still possible
Carbon tax via credit cards : ‘the polluter pays’
Complete re-think on our food policy : what we eat and where it comes from.
Vegetarian, Vegan ; Localism
Abolish all forms of Carbon trading within the EU and the world.
(3) What would be incredibly difficult to implement? ........ would any
Government stay in power a month if even suggested?
Population policy : limit access to the Welfare State for n > a certain value
(4) What about world population?
3.3 billion in 1964, 7.3 billion in 2014, possibly 11.0 billion in 2100. HELP!!!
Hugely enhanced role for the United Nations
The Catholic Church must be brought on board