Global warming?It’s a forecasting problem

J. Scott ArmstrongThe Wharton School, U. of Pennsylvania, PA

armstrong@wharton.upenn.edu

Kesten C. GreenUniversity 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)

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.

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The three-legged stool for climate policy

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

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Application of the Forecasting Audit to global mean temperatures

The Forecasting Audit requires knowledge of evidence-based forecasting methods and of the situation.

Audit by Green & Armstrong of procedures used for the IPCC “business as usual” global mean temperature scenario revealed:

72 of the 89 relevant forecasting principles were violated (e.g., “Compare reasonable methods,” “Full disclosure of data and methods”).

Would violations of evidence-based principles be acceptable in medicine or engineering?

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Application of the Forecasting Audit to polar bear policy

Averaging across two government-sponsored papers that forecasted polar bear populations:

46% of the principles were clearly violated 23% were apparently violated

Example: The project was titled “USGS Science Strategy to Support US Fish and Wildlife Service Polar Bear Listing Decision.”

Make sure forecasts are independent of politics

Starting with a growth trend in the polar bear population, they forecasted a sharp and rapid fall. We forecasted a slow growth.

Armstrong, Green & Soon (2008) Armstrong’s Senate Testimony

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Golden Rule of Forecasting: “Be Conservative” or

“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.

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When to be conservative

All forecasting problems…

especially when the situation is:1. Complex2. Uncertain3. Prone to bias, such as for:– public mass transit proposals– climate change

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Golden Rule of Forecasting Checklist

Procedure: By logic, we developed 28 guidelines for being conservative.

Tested validity by analyzing prior comparative studies.

1. Directional effects were consistent with the GR in all of the 109 papers with comparative tests of accuracy.

1. The use of a typical guideline reduced forecast error by an average of 31% in 70 papers that tested effect sizes.

The “Golden Rule of Forecasting” was published in 2015

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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.

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Simple ForecastingSimplicity in forecasting requires that reasonably intelligent clients

understand the1. method,

2. representation of cumulative knowledge,

3. relationships in models,

4. relationships among models, forecasts, and decisions

We reviewed effects of complexity on accuracy in published research from all areas of forecasting (32 papers with 97 comparisons):

a) None of the papers found that complexity helped accuracy

b) Complexity increased error by 27% on average across papers“Simple versus complex forecasting: The evidence” was published June 2015.

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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.

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Validation over different time-periods: Similar results

From Forecasting Global Climate Change (2014)13

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.

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