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Abstract

1. Policy decisions require scientific long-term forecasts of temperature, the impacts of temperature changes, and effects of policies – No scientific forecasts exist 2. Climate data and knowledge are uncertain, and climate is complex – The situation calls for simple methods and conservative forecasts 3. The no-change benchmark performs well – IPCC projection errors are 12 times higher for long-term. 4. Causal policy models with CO2 have low credibility and poor validation. 5. AGW alarm analogous to many failed predictions.
Forecasting for climate policy:
CO2, global temperatures, and alarms
J. Scott Armstrong
The Wharton School, U. of Pennsylvania, USA
armstrong@wharton.upenn.edu
Kesten C. Green
Business and Economic Forecasting, Monash University, Australia.
kesten@me.com
Andreas Graefe
Karlsruhe Institute of Technology, Germany
graefe@kit.edu
Willie Soon
Harvard-Smithsonian Center for Astrophysics, USA
wsoon@cfa.harvard.edu
International Symposium on Forecasting, Hong Kong
June 2009
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What information would change your opinion
that we face “dangerous manmade
global warming”?
How many skeptical scientists would there
need to be to persuade you that “the science”
is not settled; that there is no “scientific
consensus”?
10 scientists? 100? 1,000? 10,000?
How long would a flat or cooling trend in
temperatures need to be to persuade you that
the globe is not warming dangerously?
1 year? 2? 5? 10? 20? 100?
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Your beliefs about recent history
Extent of warming in past decade?
[___] +2 Up substantially
[___] +1 Up slightly
[___] 0 Negligible change
[___] -1 Down slightly
[___] -2 Down substantially
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Change (per month) over: All satellite history 0.001
Last 10 years 0.001
Last 5 years -0.002
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Do#almost#all#scien-sts#believe#that#
manmade#global#warming#poses#a#threat?##
Climate scientists from a 27 country survey were
not confident that scientists can make reasonable
predictions of climate for10 years (68%) or 100
years (73%) (Bray & von Storch 2007)
U.S. Senator Inhofe’s 700+ list of dissenters
Manhattan Declaration: 1,000+ scientists skeptical
Robinson Petition: 31,000+ scientists dispute
dangerous AGW
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Are scientists’ opinions
based on studies?
The Claim: Published journal articles on climate
show that almost all climate scientists believe in
dangerous manmade global warming (Oreskes
2004 claimed none of 928 “global climate
change” abstracts rejected AGW).
Oreskes survey was found wanting by Peiser
(2005), and
Schulte (2008) found 6% of 539 papers rejected
AGW while 7% explicitly endorsed AGW.
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Does it matter what
scientists believe?
Research over nearly 80 years has
shown that scientists’ opinions
are irrelevant for forecasting in
situations such as this… high
uncertainty, complex situation,
poor feedback
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19
Can experts make useful
climate forecasts?
Armstrong (1978) summarized studies: people with
much expertise are no better at forecasting than
those with little expertise.
Tetlock (2005): evaluated
• 82,361 forecasts
• made over 20 years
• by 284 professional commentators and
advisors on politics and economics
and found that expertise did not lead to better
forecasts.
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Yet, global warming is
a forecasting problem
The climate has changed and will continue to
change.
The 20th Century went through two “ice-age”
scares and two “warming” scares.
Overall, some gradual warming over past 160
years.
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11 11
Hadley annual temperature 1850-2008
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The question is, can we forecast
what will happen over the 21st
Century?9
A trend is a trend is a trend
But the question is, will it bend?
Will it alter its course
Through some unforeseen force
And come to a premature end?
Cairncross (1969)
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13 13
Audit of IPCC forecasts
IPCC “projections” of global temperature
change used improper procedures.
Green & Armstrong (2007) audit showed:
1.IPCC authors violated 72 forecasting
principles.
2. Forecasts by scientists, not scientific
forecasts.
3. No proper evidence on predictive
validity
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No scientific forecasts to date
Climate is complex.
Much uncertainty:
causes of changes are disputed,
causal factors are difficult to forecast,
data are subject to error.
In such conditions, climate models, even if properly
developed as forecasting models, are likely to be
inferior to the simple naïve models, which assumes
complete ignorance about climate.
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15 15
Conditions favor conservatism
Many opinions by experts, but no
evidence that the climate is different
now.
Thus, the naïve method would be the
preferred method based on the
conditions. We suggest this as the
benchmark model.
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16 16
Test of the benchmark
Used UK Hadley Centre’s “best estimate” of global
mean temperatures from 1850 to 2007
(HadCRUt3)
Forecast for up to 100 subsequent years on
rolling horizon
157 one-year-ahead forecasts…
58 hundred-year-ahead forecasts
10,750 forecasts across all horizons
Absolute errors calculated vs actual (HadCRUt3)
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Expecta-ons#about#the##
benchmark#model#
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Naïve (no-change) benchmark model forecast errors
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Validity of IPCC projection
1992 IPCC report’s 0.03oC/year linear
projection
Test vs benchmark for
1992 to 2008 pure ex ante
1851 to 1975 simulated ex ante*
* advantage to IPCC vs benchmark model
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20 20
Mean errors 1992-2008
Using UAH satellite data and rolling
forecasts,
Averaging the mean absolute errors
for all 17 horizons…
Benchmark 0.215 oC
IPCC projection 0.203 oC
Difference 0.012 oC
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21 21
IPCC performance 1851-1975
(long range; ex post warming trend)
CumRAE* of IPCC/Benchmark Ratio
Ratio n
From 1850 only 10.1 125
Rolling (1-100 years) 7.7 7,550
1-10 years 1.5 1,205
41-50 years 6.8 805
91-100 years 12.6 305
* CumRAE < 1 means forecast errors smaller than
benchmark errors
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;;9
The Global Warming Challenge
“The Climate Bet”
Predict global mean temp over 10 years.
- Al Gore (An Inconvenient Truth”) to select any current
climate model
-Scott Armstrong will forecast no change
Each deposits $10,000 in a trust fund in Dec. 2007. Value to
winners charity in 2018.
1.Proposed June 19, 2007 with Dec. 1, 2007 deadline
2.Mr. Gore replied -- too busy.
3.Armstrong simplified check one box & sign name -- &
extended deadline to March 26, 2008.
4.Mr. Gore replied he does not make financial bets.
5.Armstrong dropped the financial part and suggested that
the challenge be done simply in the interests of science.
Details at theclimatebet.com
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23 23
Armstrong-Gore bet expectations
Based on the Hadley data for 1850 through 2008*…
Assuming Gore followed IPCC forecast of 30C per
century, Armstrong has a probability of wining
bets against the 0.03oC/year trend of
0.54 for one-year-ahead forecasts; n=158
0.57 for three-year-ahead forecasts; n=156
0.68 for ten-year-ahead forecasts; n=149
* which, as we know, was a warming period
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Armstrong#leads#on#monthly(results#
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25 25
Alternatives to the benchmark
1.Causal model with atmospheric CO2*;
alternative variables?
2.Prediction markets
3.Predictions about global warming alarm
from outcomes of analogies
*CO2: concentration of carbon dioxide in the atmosphere in
parts per million (ppm); also referred to as the CO2 mixing
ratio.
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What#causes#temperature#change?#
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Hadley Temperature Series
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y = 0.0003x - 0.324
R2 = 0.72
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Hadley Temperature Series
Price Index
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R2 = 0.72
Hadley Temperature Series
Postal Rates
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y = 0.0082x - 2.72
R2 = 0.74
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Hadley Temperature Series
CO2
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Correla-ons#between#global#temperatures#
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Causal model testing procedures
Data: Global mean temperature: HadCRUt3 1850- 2008
CO2: Total global atmospheric concentration, NASA
Models: First differences*; levels**
Estimated initially using 1850-1899 data
Forecasts: Annual
Rolling forecasts for up to 100 years
Updated estimate of relationship each roll
Conditional on knowing CO2
*Temp t – Temp t-1 ~ CO2 t-1 – CO2 t-2
**Temp t ~ CO2 t
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CO2 policy implications? Or not?
Our tentative first round results, show little relationship
between CO2 and global mean temperature.
E.g. Forecast of the effect of stopping man-made CO2
emissions altogether for the next 100 years:
Model Effect on temp by end of 100 years
1st differences increase mean temperature by 0.40oC
Levels decrease mean temperature by 0.24oC
As noted, these are only a rough first go. Additional studies
are warranted, given the uncertainty.
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Related#predic-on#market##
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44 44
Forecas-ng#by#Structured#Analogies9
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45 45
Structured analogies procedures
1. Ask heterogeneous group* of experts to
individually describe as many analogies as they
can for the current AGW situation.
2. Experts then rate analogies for similarity to the
AGW situation.
3. Mechanical summary based on what happened in
the analogous situations: (Forecasts based on the
set of “most similar” analogies).
* Recruit warmers, skeptics, and others.
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Structured#analogies#exercise##
on#alarms#
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Rate#the#alarm#analogies#in#the#
ques-onnaire#
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Structured#analogies#process#
Please describe, below !
aSituations that are analogous to the current alarm over manmade global warming!
bThe source of your knowledge about them (e.g. academic research, general
knowledge, personal experience…)!
cSimilarities and differences between your analogies and the manmade global
warming alarm!
dHow similar to manmade global warming? (1 = Slight similarity… 10 = Great
similarity)!
eWas the warning justified? (0 = No, not at all… 10 = Yes, entirely)!
fWere recommended actions taken? (0 = No, not at all… 10 = Yes, entirely)!
gHow did the benefits of the actions that were taken compare with the costs of those
actions? !
!(-5 = Costs greatly exceeded benefits… 0 = Neutral, no net benefit or cost… +5 =
Benefits greatly exceeded costs)
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10 of the 40 analogies suggested to date
1. 1970s cooling and fear of consequences of a new Ice Age
2.Ehrlich’s “The Population Bomb” fear of resource shortages
3.Calls to avoid eating fish due to presence of mercury
4.2nd-hand tobacco smoke and lung-cancer and heart disease
5.Alarm over effects of alcohol and calls for abolition
6.Recreational drug taking concerns and resulting criminalization
7.Cancer from breast implants
8.Fear that “acid rain” would destroy the World’s forests
9.Concern about economy and Roosevelt’s New Deal response
10.Natural radon in homes and lung cancer
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First#impression#from#analogies#
Another story for “Extraordinary popular
delusions and the Madness of Crowds”?
[Charles MacKay 1841]
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A Forecaster’s Summary
1. Policy decisions require scientific long-term
forecasts of temperature, the impacts of
temperature changes, and effects of policies
No scientific forecasts exist
2. Climate data and knowledge are uncertain, and
climate is complex
The situation calls for simple methods and conservative
forecasts
3. The no-change benchmark performs well
IPCC projection errors are 12 times higher for long-term.
4. Causal policy models with CO2 have low credibility
and poor validation.
5. AGW alarm analogous to many failed predictions.
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Forecasters#can#make#contribu-ons#
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When#beliefs#are#strong,#only#self
persuasion#is#possible#
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References#
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?4N7Q9
3=.T_3T]//9P<1H1RQ$f(&,&4"(9!&'$()*+,->9F4*0*%64$?*&-0.,9$GH>9D1D6I<;Q$
3=efTfT>93Q9P<11IRQ93),9=**$59e)'M$5*9a$9e),"BJ#)5$LX9=9!"$#L9f^B$'"4$,59O"5K9T)($5')(M9a$u,->9?*&-0.,$*7$I*,6/4.,$F4*0*%D>9
JKL>9FGD6FI;Q99
?]Tf>9=Q9P;00HRQ9;0$604*0M#06#0($(-&(2C$:2#$+,.0#(.-D$#%#-1#04D$*7$1,*E.,$N.-%601$.05$N2.($N#$4.0$5*$.E*&($6(Q9f44)J*>9[=%9
T&L)#$9['$**)$9
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JO>9_&Q9DvI>911G6<0<1Q9
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T7]mf>9[Q9WQ9A9/VTUe[!>98Q9/Q9P;00FRQ97"*5&'"()#9['$*"L$,+)#9a$u,-9e)'M$5*>9?*&-0.,$*7$F4*0*%64$I#-'+#4/M#'9$JO>9<;D6<F<Q999
/37UwVf98Q9eQ9P;00IRQ9/("$,+l(9(&,*$,*J*9&,9(#"4)5$9(K),-$X9F0#-1D$T$F0M6-*0%#0(9$JH>9;I<6;IHQ9
VfVw]38>9[Q9fQ9P;00GRQ9FW+#-($+*,6/4.,$3&51%#0(C$X*N$1**5$6'$6(Y$X*N$4.0$N#$Z0*NY9['",($5&,>9_p%9['",($5&,Q99
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“The Precautionary Principle”
It is a political principle. . . if the government is persuaded
that there is a risk with a high possible cost, there is no
need for a rational analysis.
Contrary to scientific analyses of costs and benefits.
Brings to mind the slogan on the Ministry of Truth building
in George Orwell’s 1984: “Ignorance is Strength.
Scientific forecasting suggests appropriate policy decision is
“don’t just do something, stand there!”
For more see “Evidence-based forecasting for climate
change: Uncertainty, the Precautionary Principle, and
Climate Change” on theclimatebet.com Sept 1, 2008
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ResearchGate has not been able to resolve any citations for this publication.
Article
The intelligence failures surrounding the invasion of Iraq dramatically illustrate the necessity of developing standards for evaluating expert opinion. This book fills that need. Here, Philip E. Tetlock explores what constitutes good judgment in predicting future events, and looks at why experts are often wrong in their forecasts. Tetlock first discusses arguments about whether the world is too complex for people to find the tools to understand political phenomena, let alone predict the future. He evaluates predictions from experts in different fields, comparing them to predictions by well-informed laity or those based on simple extrapolation from current trends. He goes on to analyze which styles of thinking are more successful in forecasting. Classifying thinking styles using Isaiah Berlin's prototypes of the fox and the hedgehog, Tetlock contends that the fox--the thinker who knows many little things, draws from an eclectic array of traditions, and is better able to improvise in response to changing events--is more successful in predicting the future than the hedgehog, who knows one big thing, toils devotedly within one tradition, and imposes formulaic solutions on ill-defined problems. He notes a perversely inverse relationship between the best scientific indicators of good judgement and the qualities that the media most prizes in pundits--the single-minded determination required to prevail in ideological combat. Clearly written and impeccably researched, the book fills a huge void in the literature on evaluating expert opinion. It will appeal across many academic disciplines as well as to corporations seeking to develop standards for judging expert decision-making.
Article
Review of J. Scott Armstrong's 1978 book on forecasting. Click on the DOI link above to read the review
Article
This book is published to tie in with a documentary film of the same name. Both the book and film were inspired by a series of multimedia presentations on global warming that the author created and delivers to groups around the world. With this book, Gore, brings together leading-edge research from top scientists around the world; photographs, charts, and other illustrations; and personal anecdotes and observations to document the fast pace and wide scope of global warming. He presents, with alarming clarity and conclusiveness, and with humor, too, that the fact of global warming is not in question and that its consequences for the world we live in will be disastrous if left unchecked.
The Population Bomb" fear of resource shortages story for "Extraordinary popular delusions and the Madness of Crowds
  • Ehrlich
Ehrlich's "The Population Bomb" fear of resource shortages story for "Extraordinary popular delusions and the Madness of Crowds"? [Charles MacKay 1841] 50
CanAssetMarketsBeManipulated?AFieldExperimentwithRacetrackBeung
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CAMERER,C.(1998).CanAssetMarketsBeManipulated?AFieldExperimentwithRacetrackBeung, Journal of Poli/cal Economy, 106,457-482.
The assault on reason
  • A Gore
GORE,A.(2007).The assault on reason.NewYork:Penguin.
  • M Schultek
SCHULTEK.M.(2008).Scien+ficconsensusonclimatechange? Energy & Environment, 19,281-286.
Scientific forecasting suggests appropriate policy decision is "don't just do something, stand there!" For more see "Evidence-based forecasting for climate change: Uncertainty, the Precautionary Principle, and Climate Change
  • George Orwell
George Orwell's 1984: "Ignorance is Strength." Scientific forecasting suggests appropriate policy decision is "don't just do something, stand there!" For more see "Evidence-based forecasting for climate change: Uncertainty, the Precautionary Principle, and Climate Change" on theclimatebet.com Sept 1, 2008