Global warming? It’s a forecasting problem J. Scott Armstrong The Wharton School, U. of Pennsylvania, PA [email protected]Kesten C. Green University of South Australia, Adelaide Presented at the ICCC Ten, Washington, D.C. June 11, 2015 Available at http://www.kestencgreen.com/A&G-ICCC-10.pdf (R-25)
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Global warming? It’s a forecasting problem J. Scott Armstrong The Wharton School, U. of Pennsylvania, PA [email protected] Kesten C. Green University.
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Global warming?It’s a forecasting problem
J. Scott ArmstrongThe Wharton School, U. of Pennsylvania, PA
What is evidence-based (scientific) forecasting?1. The Forecasting Principles Project was undertaken in the late
1990s to summarize experimental findings; it involved contributions by…
40 experts in various disciplines120 independent reviewers.
• The project gave rise to 140 principles (condition-action statements) that are available online for free as a checklist to guide forecasters. See Principles of Forecasting and the Forecasting Audit. Do forecasters comply with the principles?
• The validated (scientific) principles apply to all areas of forecasting—no forecasting task is exempt.
• To our knowledge, there are no other summaries of scientific forecasting principles.
Rational climate policy requires scientific forecasts of:1. substantive long-term trend in global mean temperatures2. major net harmful effects from changing temperatures3. net benefit from proposed policies relative to no action.
Failure of any leg means policy action is unsupported.
IPCC makes no claim to use scientific forecasts. They state that “long-term prediction of future climate states is not possible”.
There are no scientific forecasts to support any leg.
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Warming alarmists do not forecast, they create “scenarios” via computer simulations
1. Scenarios are:a. Stories… about “what happened in the future”b. Biased… so do not provide valid forecasts
(Gregory & Duran, 2001).
2. The stories are based on expert judgments. According to prior research, expert judgments about what will happen in complex, uncertain situations are useless:a. Seer-sucker Theoryb. Tetlock’s 20-year experiment
“Forecast unto others as you would have them forecast unto you.”
Be conservative by adhering to cumulative knowledge about:1.the situation, and2.evidence-based forecasting methodsThe “Golden Rule of Forecasting” was published in June 2015.
Golden Rule applied to IPCC scenarioGolden Rule of Forecasting Checklist was used to evaluate IPCC “business as usual” global warming scenario and no-change model forecasts.
Consensus ratings by Armstrong and Green indicated that of 20 relevant Golden Rule Checklist guidelines:• the IPCC scenarios followed none• the no-change model followed 95%
Don’t believe us? Rate them yourself and send us your ratings and reasons!
Tests of forecast accuracy over the 1851-1975 forecasting period yielded 58 forecasts for horizons of 91 to 100 years.
Average error (MAE) of no-change forecast for 50-year horizon was 0.24°C.
Errors from the IPCC scenario of .03°C warming-per-year were 12.6 times larger than those from the no-change model forecasts.
Simple Forecasting Checklist ratings:IPCC projections vs. no-change forecasts
Our Average Compliance Ratings (% of perfect score) IPCC No Change
19 96 Ratings can be done by novices in forecasting.Do you own and send us your ratings and reasons!Recall that…
Tests of forecasts over the 1851-1975 forecasting period yielded 58 forecasts for horizons of 91 to 100 years. The errors of these IPCC forecasts were 12.6 times larger than those from the easily understood no-change model.
Why are complex methods used by global warming alarmists?
Complex methods impress people when they are used by people who appear to be experts (e.g., doctors, academics, lobbyists, politicians).
Complex methods allow clients to obtain the forecast they prefer.
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Analysis of previous environmental alarmsWe obtained 71 proposed analogies. 26 met our criteria that the alarm be:
(1) based on forecasts of human catastrophe arising from effects of human activity on the physical environment,
(2) endorsed by experts, politicians, and the media, and (3) accompanied by calls for strong action.
None of the 26 alarms were based on scientific forecasting procedures.
None of the alarming forecasts were accurate.
Governments took action in 23 of the analogous situations
The government actions were harmful in 20 situations (3 were uncertain).
Thus, we predict that the Global warming alarmist movement will eventually
fail, but will cause ongoing harm via entrenched public policy responses.
The global warming alarm: Forecasts from the structured analogies method
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Policies should be based on scientific forecasts: To date, none are
No one has challenged our finding of the invalidity of the IPCC alarming warming scenario. Nor has anyone challenged the scientific forecasts of long-term global mean temperatures by Green, Armstrong, & Soon (2009) other than via ad hominem attacks (e.g., the Willie Soon Affair).
The IPCC’s single hypothesis approach is inconsistent with the scientific method. It is a strong source of bias.
We urge other researchers to test our findings by replication or by extensions using alternative plausible hypotheses of long-term global climate—namely, cooling, no change, and warming.
For ongoing research on forecasting aspects of the global warming alarm, see theclimatebet.com and publicpolicyforecasting.com.