lecture 2 anthropogenic climate change - the current state of knowledge and skepticism
TRANSCRIPT
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LSGI1B022013-2014 (Semester 3)
Leung Wing-mo
Climate Change and Society
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Anthropogenic climate change: the current state
of knowledge and skepticism
Lecture 2
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More about greenhouse effect
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Climate as a system consisting of the atmo
Global warming and Climate change :
It’s all about energy and energy balance
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Energy transfer
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Energy in the form of Electromagnetic Wave
3G Earth
Sun
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Temperature and radiation
max
b/T
energy 0°C = 273.15K
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Stars inside the globular cluster Omega Centauri
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Lovejoy, Jan 2015
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Electromagnetic spectra : Sun vs Earth
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The Electromagnetic Spectrum Song - by Emerson & Wong Yann
song
Hyperlink:
http://www.youtube.com/watch?v=bjOGNVH
3D4Y
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Atmospheric influences on radiation
Reflection Scattering Absorption
(absorber
warms)
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Reflection
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Scattering – why the sky is blue
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Scattering – why sunset is beautiful
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Atmospheric absorption and scattering of main Greenhouse Gases (GHG)
Water vapour
windows
Water vapour is an
important GHG, but:
• a gap in
absorption
• very little high up
• a feedback rather
than driver
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Greenhouse effect
http://www.youtube.com/watch?feature=play
er_detailpage&v=ZzCA60WnoMk
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Earth’s energy budget (approximate, averaged
over the whole globe and over a long time)
At the top of the atmosphere:
Incoming shortwave = Reflected Shortwave + Emitted longwave
At the surface:Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming)
+ Latent heat flux + sensible heat flux
Sensible
heat 7%
Latent heat
23%
Net Longwave 21%
Yellow:
shortwaveRed:
longwave
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Energy budget of the Earth (accurate)
Trenberth et al, AMS, 2009
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Increasing GHG is
equivalent to reducing
the size of the drain in
the bathtub.
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Our Earth – resembling this car?
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Global
warming =
4 Hiroshima
bombs every
second !
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Where does the extra energy go to?
What is scary is that many of
us don’t even know about it!
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Key points
Shortwave radiation from the sun is the ultimate source of energy for
Earth’s climate system.
About 30% of incoming solar radiation gets reflected directly back to
space.
Earth absorbs energy from 2 sources: incoming solar energy and
energy re-emitted back toward Earth by GHG.
Earth therefore heats up to a temperature at which it can radiate
enough energy such that its energy outflow will balance its energy
inflow.
Earth is currently out of balance, with inflow exceeding outflow. It’s
temperature will rise until inflow and outflow are back in balance.
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Key points (cont)
GHG are those that absorb and re-emit IR in the wavelength range of
IR emitted by Earth.
The major components in our atmosphere, N2 and O2, are symmetrical
and are not GHG. CO2, H2O etc have many modes of vibration which
facilitate absorption of IR.
When GHG emit IR, they emit it in random direction:
Some goes back towards Earth and gets re-absorbed
Some goes toward space
Some goes to another GHG molecule which repeats absorption and re-emission
and sends the energy in another random direction.
GHG slow the passage of IR from Earth’s surface to space, warming
the planet.
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Changes associated with global warming
‘You don’t need people’s opinions on a fact’
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1.1 Temperature - annual global temperature anomaly (wrt 1979 – 2010)
(satellite)
(surface)
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1.2 Temperature – cold nights and days
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1.3 Temperature – warm nights and days
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1.4 Temperature – spatial variation
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2 Ocean - warming of the upper layers
Global ocean heat content 較深的海水攝取更多熱能
較淺的海水
1022J = 150,000,000 Hiroshima bomb
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4 Sea ice - the decrease in the last 30 years is unprecedented in the past 1450 years
1-3月
4-6月
10-12月
7-9月
Nov 1, 2011
Nov 1, 1980
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5 Ice sheet - accelerating loss
Greenland ice sheetAntarctica ice sheet
RED:loss of iceBLUE:increase of ice
2003-2012
南極冰蓋 格陵蘭冰蓋
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5 Melting ice sheet
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6 Snow cover in N. hemisphere -decreasing
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6 Vanishing glacier
vanishing glacier
http://www.bbc.co.uk/news/world-south-asia-15216875
2012
1983
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6 Melting glacier
阿拉斯 (Muir Glacier, Alaska's Glacier Bay)
13 August 1941 31 August 2004
The glacier retreated by more than 12 km and thinned out by more than 800 m
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7 Sea level – rising since mid 19th
century
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7 Rising sea level
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Source: WMO, http://www.wmo.int/pages/mediacentre/news/documents/400ppm.final.pdf
鑑古知今Current concentration
CO2 concentration now is the highest in the past 800,000 years
800,000 yr
8 Carbon dioxide concentration
https://www.youtube.com/watch?v=bak50U6HiRk
White elephants in the sky :
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9 Acidification of the ocean
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Independent analyses of many components of the climate system that would be expected to change in a warming world exhibit trends consistent with warming (AR5)
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Overwhelming evidence of climate change
John Oliver HBO show “Climate debate”:
‘You don’t need people’s opinions on a fact.’
http://www.washingtonpost.com/blogs/erik-wemple/wp/2014/05/12/john-
oliver-on-climate-change-skeptics-you-dont-need-peoples-opinions-on-a-fact/
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Skepticism
“I say the debate is over.
We know the science. We
see the threat. The time
for action is now.” – Arnold
Schwarzenegger, 2006
But is the debate over?
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A fundamental question:“How do we know our current science is not wrong?” We don’t! But …
Examples of science of consensus overturned:
Geocentric universe
Fixity of species
Absolute nature of time and space, pervaded by aether
Fixity of continents
Yes, we could be wrong, and if scientific research
continues, it is almost certain that some aspects
of the current understanding will be modified,
perhaps in significant ways. But …
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The robustness of climate science is thoroughly tested through:
(1) Induction (歸納法, generalizing from specific
examples): The more we know about a subject, the
more likely our conclusions about it are to be true.
Temperature records show a strong increase in temperature
when the amount of CO2 grew dramatically.
Instrumental records collaborated by independent evidence
from tree rings, ice cores, coral reefs etc.
Induction is not a sufficient condition. But the more
we know about a subject, the longer we’ve studied it,
the more likely our conclusions about it are true.
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The robustness of climate science is thoroughly tested through: (2) Deduction (演繹推理, drawing inferences/predictions from
hypothesis): The most famous historical example of successful
deduction is that of Ignaz Semmelweis (1840s) about prevention
spread of infection by washing hands.
Svante Arrhenius, G S Callendar, Han Suess – independently predicted the
consequences of increasing CO2, and the prediction has come true.
Suki Manabe predicted warming strongest in polar regions, is not an induction
from observation but deduction from theory (Polar amplification – ice-albedo
feedback)
But still, we could be right for the wrong reason. One can never prove
a theory true, but you can prove it false – falsificationism (testability).
Climate predictions could be wrong, but if such mistakes are found,
there is no guarantee that correcting them will lead to a more
optimistic scenario. In fact, climate predictions have so far been
conservative than not.
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The robustness of climate science is thoroughly tested through:
(3) Consilience of evidence
(independently derived data sets
coincide and explicable by the
same theory, coming together, like
a jigsaw puzzle.)
Instrumental records, tree rings, ice
cores, borehole … all point to the
same conclusion – things are getting
warmer.
Warming sea surface, melting glacier,
tree distribution… explicable only by
global warming.
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Evidential standards – the evidence has been
subject to replication, corroboration and
peer review.
On the contrary, the contrarians are those
that fail the peer review
Climate science satisfies any criterion we put forward to test it
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Merchants of doubts
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Internal inconsistency of climate deniers–a denier holding 3 inconsistent beliefs at the same time
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He was partly to be blamed
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Interestingly, Reagan’s bonded ally, Margaret Thatcher, was a climate hawk
• The enormous changes
concentrated in such a short
time, … we have begun a
massive experiment with the
systems of this planet .
• No generation has a freehold
on this earth. All we have is a life
tenancy – with a full repairing
lease.
•We are not the lords, we are the
Lord's creatures, the trustees of
this planet, charged today with
preserving life itself—preserving
life with all its mystery and all its
wonder. May we all be equal to
that task.
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Prominent scientists started the defamation campaign against climate scientists – motivated by politics/vested interest/ideology
William Nierenberg,
Director of Scripps
Institute of
Oceanography
Robert Jastrow
Head, Goddard
Institute for
Space Studies
Frederick Seitz
President, NAS,
Consultant to
Reynolds
Tobacco
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George C Marshall Institute Think Tank, 1980’s
Challenged the scientific evidence, insisting that it was highly uncertain,
and there is no consensus;
No evidence of warming, or if there is warming, it is due to the sun (not
GHG);
Even if there is warming, it doesn’t matter, because we’ll just adapt to it;
Climate change is a hoax;
All because they have been fighting an enemy (Soviet Union) all life
long, and when Soviet enemy was gone, they had to find a new
enemy – environmental “extremism”.
They applied the “tobacco strategy” – unsettled science, no consensus.
“Doubt is our product” – infamous memo written by one tobacco
industry executive in 1969 – since it is the best means of competing
with the “body of fact” that exists in the mind of the public.
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Global Climate Coalition, US, 1989 -2002 Amoco,
the American Forest & Paper Association,
American Petroleum Institute,
Chevron,
Chrysler,
Cyprus AMAX Minerals,
Exxon,
Ford,
General Motors,
Shell Oil,
Texaco,
United States Chamber of Commerce
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2003 internal memo from Republican Advisor Franck Luntz to Candidates
The Party has lost the environmental communication battle, and is vulnerable on
environmental issue including climate change because people care about
environment and believe the government should do something.
The scientific debate is closing (against us) but not yet closed. There is still a
window of opportunity to challenge the science.
In order to address the vulnerability, Frank Luntz advised that we (Republicans)
should:
Insist that we don’t know whether climate change is a problem – that the science is
uncertain and hence it is premature for the govt to act on something which is not certain.
Act only with all the facts in hand (a recipe for inaction)
The scientific debate remains open. Should the public believe that the scientific issues are
settled, their views about global warming will change accordingly.
Use phrases “climate change” rather than “global warming”, since “climate change” is a lot
less frightening than “global warming”
He added, “A compelling story, even if factually inaccurate, can be more
emotionally compelling than a dry recitation of the truth.”
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Doubt mongering strategies
Exploit complexity of issue
“Many unresolved questions”
Take details out of context
Confuse people with true but irrelevant information
Exploit scientific uncertainty – it isn’t proven
Create impression of scientific debate
Highlighting and exploiting real but minor dissent
Taking small disagreements about details out of context
Scientific Potemkin Village
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Famous examples of doubt of contrarian : You can’t be sure that smoking cause cancer!
Smoking is not the only environmental factor
(besides asbestos, radon, air pollution…), hence you
cannot single it out as the cause.
But the fact is, through epidemiological studies:
among people who smoke but not exposed to
asbestos etc., they get lung cancer at much higher
rates than non-smokers. This leaves smoking as the
best explanation.
Dose-response relationship: more smoking > more
cancers (for the population).
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A passage from the book “Merchants of Doubts” - Naomi Oreskes
"Imagine a gigantic, colossal banquet. Hundreds of millions of
people come to eat. They eat and drink to their hearts' content,
eating food that is better and more abundant than at the finest
tables in ancient Athens, or Rome or even in the palaces of
medieval Europe.
Then one day a man arrives wearing a white dinner jacket. He
is holding a bill."
"Not surprisingly the diners are in shock. Some begin to deny
that this is their bill. Others deny that there even is a bill. Still
others deny that they partook of the meal. One diner suggests
the man is not really a waiter, but is only trying to get attention
for himself or to raise money for his own projects. Finally the
group concludes that if they simply ignore the waiter, he will go
away.
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It is up to the deniers to say that the current level of carbon dioxide is not
bad
1. Anthropogenic carbon dioxide levels are less important in driving climate
change compared to the greenhouse effect of clouds and water vapour.
2. There is no correlation between carbon dioxide and temperature, let alone a
demonstrated causal relationship. This is supported by the fact that the
steadily rising level of carbon dioxide, …, does not correlate with temperature
trends. There has been no global warming for 17 years, despite ever-
increasing levels of carbon dioxide.
3. …
Wyss Yim, Pok Fu Lam, Hong Kong
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Anthropogenic carbon dioxide levels are less important in driving climate change compared to the greenhouse effect of clouds and water vapour - Yim
WarmingCooling
Aerosols partly
offset the warming
of GHG
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“There is no correlation between carbon dioxide and temperature, let alone a demonstrated causal relationship” - Wyss Yim
But the fact is : CO2 absorbs IR was settled science more than
100 years ago.
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“There is no correlation between carbon dioxide and temperature, let alone a demonstrated causal relationship” (cont.)
Svante Arrhenius, calculated in 1896 that cutting CO2 in half would suffice
to produce an ice age. He further calculated that a doubling of
atmospheric CO2 would give a total warming of 1.5-4.5 degrees Celsius.
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“There has been no global warming for 17 years, despite ever-increasing levels of carbon dioxide” – Wyss Yim
Deliberately choosing 1998,
the warmest year on record,
as the starting point
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“Global warming stopped 16 years ago !”Wyss Yim is not the first one to make this claim
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69
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January 2014, one of the
coldest in North America
A case of confusing
people with true but
irrelevant information
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Trump controversies:
• Racial
discrimination – full
page newspaper ads
calling for death
penalty of black
teenage suspects in a
rape case; alleging
Obama didn’t get good
enough grades to
Harvard; “laziness is a
trait in blacks”…
• Vaccines cause
autism
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Despite what Trump said, the Earth is still warming !
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IPCC AR5 (2014) : “It is extremely likely (>95% confidence) that human influence has been the dominant cause of the observed warming since the mid-20th century.”
Is 95% confidence good enough to call for action?
Should we wait and see?
Uncertainty is inherent in every scientific judgment, demanding
absolute proof on issues as complicated as climate change does not
make sense.
95 % certainty regarding climate change is most similar to the
confidence scientists have that cigarettes are deadly.