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Do We Face Dangerous Global Warming? A Presentation by J. Scott Armstrong and Kesten Green

June 7, 2019

This is the PowerPoint presentation at the Invited Lecture for the Class of 1959 Reunion at Lehigh University, Bethlehem, PA on June 7, 2019

Opening slide:

“I would rather have questions that can't be answered than answers that can't be questioned.”

- Richard Feynman

Second slide:

Warming alarmists do not forecast; they create “scenarios” to use in computer simulations

1.The scenarios (stories) are based on some scientists’ opinions. The scenario method has never been shown to provide valid forecasts (Gregory & Duran, 2001).
2.Expert judgments about what will happen in complex, uncertain situations are no better than non-experts’ opinions, and are often no better than chance:
a.Seer-sucker Theory. “No matter how much evidence exists that seers do not exist, suckers will pay for the existence of seers.”
b.Tetlock’s 20-year experiment on experts’ judgmental forecasts supports the Seer-Sucker theory.

Third slide:

The Global Warming Forecasts Violate Valid Forecasting Principles

1.The Principles of Forecasting Handbook (Armstrong 2001) was the product of research by 40 experts on forecasting methods, reviewed by 123 experts. The result was 139 “forecasting principles.” (available at
2.An audit by Green & Armstrong (2007) of procedures from the IPCC “business as usual” global mean temperature scenario revealed that the IPCC’s* global warming forecasts violated 72 out of 89 forecasting principles relevant to climate change. Consider an aviation engineer who would violate one principle
** Intergovernmental Panel on Climate Change (United Nations) established in 1988: ”Dedicated to providing the world with an objective scientific view of climate change.” Wikipedia

(“Scientific” was not defined.)

Tenth slide:

Armstrong’s 10-year bet with Mr. Gore:  Global climate is a complex situation with high uncertainty.

Eleventh slide:

The Climate Bet after 10 years

1.The cumulative absolute error of the “alarming” warming projection (Gore/IPCC) was 10% larger than the error of the no-change forecast.
2.The average signed error of the Gore-IPCC projection was 3.6 times larger (i.e. more biased) than no-change’s.
3.To give Mr. Gore (and the IPCC) a chance at redemption, we have extended the bet for another 10 years.
4.We are now 1 year and 4 months into the second 10 years.
5.We monitor the bet using the “Whole Earth Thermometer”
Download the whole PDF version of this presentation here, or the link above.
J. Scott Armstrong, professor at the Wharton School, University of Pennsylvania, is a founder of the Journal of Forecasting, International Journal of Forecasting, and International Symposium on Forecasting. He is the creator of forecastingprinciples.
Kesten C. Green is a senior research fellow at the Ehrenberg-Bass Institute at the University of South Australia Business School and a policy advisor to The Heartland Institute.