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Evidence-based forecasting for climate change

Archive for the ‘public policy’ Category

Complex models of climate at odds with forecasting principles predict temperatures will rocket… or plummet

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When the situation is complex and there is uncertainty about causal relationships, forecasting principle 6.6 dictates that forecasters should “Use few variables and simple relationships”. The opposite approach was used in the Intergovernmental Panel of Climate Change models, and there have been calls (1 , 2) for even more money to enable modelers to create models that are even more complex. Patrick Frank, in an article in Skeptic (2008, 14:1) titled “A climate of belief”, showed that a very simple model with CO2 as the only causal variable and using the IPCC assumptions about the direct and indirect effects of changes in atmospheric CO2 concentrations makes predictions of global average temperatures that are closer to the IPCC’s “ensemble average” of complex model forecasts than are those of any of the individual complex models. In other words, putting aside whether the forecasts are accurate or not, there is no need to have complex models in order to make those forecasts.

Frank’s simple model illustrates part of the purpose of principle 6.6; namely to aid understanding and reduce forecasting costs. We aren’t sure what the cost of the complex relative to the simple modeling efforts were but, given the number of people and computer time involved in the complex models, a ratio of 1 million to 1 is a conservative guess. Frank’s simple model is simple enough for anyone to understand. That’s a good thing, because the modeler’s assumption are clear and can be tested and disputed, and the disputation can be understood by others. This makes it easier to reject a false model and thereby to advance scientific understanding. Thus the use of simple models reduces mistakes, another purpose of the principle.

The primary purpose of many of the forecasting principles is naturally enough to improve accuracy; principle 6.6 is no exception. Frank demonstrates that the IPCC grossly under-reports the cumulative uncertainty of the model forecasts. The figure below from Frank’s article shows that, when proper allowance is made for uncertainty about the effects of clouds and greenhouse gases on global average temperatures, the complex IPCC models cannot legitimately tell us better than that the temperature change by the end of the century will be somewhere between +120-degrees-C and -120-degrees-C. It would be foolish indeed to base public policy on forecasts from such models.

Patrick Frank’s article is available from the Skeptic site.

Read this article and more at PublicPolicyForecasting.com.

Written by climatebet

June 6, 2008 at 7:53 pm

Secretary of the Interior ignores scientific evidence on forecasting, instead favoring experts’ opinions to list thriving polar bear population as threatened

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Secretary of the Interior Dirk Kempthorne announced on May 14, 2008 that he is accepting the recommendation of U.S. Fish and Wildlife Service Director Dale Hall to list the polar bear as a threatened species under the Endangered Species Act (ESA). The listing is based on the best available science, which shows that loss of sea ice threatens and will likely continue to threaten polar bear habitat. This loss of habitat puts polar bears at risk of becoming endangered in the foreseeable futures”. See the U.S. Department of the Interior website for the full announcement.

This extraordinary announcement is at odds with evidence that the polar bear population is currently thriving, and is based on false assumptions and unscientific forecasting procedures. The forthcoming Interfaces paper by Armstrong, Green, and Soon, provides evidence that the “best available science” does not support a listing.

Written by climatebet

May 17, 2008 at 10:26 pm

Polar bear fears groundless

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The U. S. government commissioned studies to support the listing of polar bears as a threatened or endangered species. Polar bear numbers are currently high and the population has been increasing rapidly in recent decades. Everyone likes polar bears, so this is good news. A decision to list would require forecasts that the current upward population trend will reverse. The government studies concluded that polar bear populations would decrease substantially.

Decision makers and the public should expect people who make forecasts to be familiar with the scientific principles of forecasting just as a patient expects his physician to be familiar with the procedures dictated by medical science. Three scientists, J. Scott Armstrong of the University of Pennsylvania, Kesten Green of Monash University, and Willie Soon of The Harvard-Smithsonian Center for Astrophysics, audited the government studies to assess whether they were consistent with forecasting principles. Their paper, “Polar Bear Population Forecasts: A Public-Policy Forecasting Audit,” has been accepted for publication in the management science journal Interfaces. It is the only peer-reviewed paper on polar bear population forecasting that has been accepted for publication in an academic journal.

They concluded that the government forecasts were based on false assumptions and their polar bear population forecasts contravened many principles for scientific forecasting. Indeed, the reports followed fewer than one-sixth of the relevant principles. Given the importance of the forecasts, all principles should be properly applied. In short, the government reports do not provide relevant information for this decision.

Research shows that for issues such as the population of polar bears—situations that are complex and where there is much uncertainty—the best forecast is that things will follow a “random walk;” in effect, this model states that the most recent value is the best forecast for all periods in the future. Because the polar bear population has been increasing over recent decades, however, a continuation of that trend over the short term is possible.

Copies of Armstrong, Green and Soon’s forthcoming paper are available at http://publicpolicyforecasting.com.

Written by climatebet

March 31, 2008 at 6:25 pm

Q&A With Senator Boxer

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Below are excerpts from the Q&A session between Armstrong and Senator Boxer. Full Text of Examining Threats and Protections For the Polar Bear.

Senator Boxer. Now, Dr. Scott, you are a Ph.D. in what? Dr. Armstrong.

Mr. Armstrong. I went to MIT, so I basically had three areas, one was economics, the other was social psychology and the other was marketing.

Senator Boxer. Economics, social psychology and marketing. Are you a biologist?

Mr. Armstrong. No.

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Written by climatebet

February 8, 2008 at 4:32 am

Q&A With Senator Inhofe

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Below are excerpts from the Q&A session between Armstrong and Senator Inhofe. Full Text of Examining Threats and Protections For the Polar Bear.

Dr. Armstrong, when you were talking, this chart up here, first of all, did you say that you had a paper that you wrote in 1978?

Mr. Armstrong. I was writing books on long range forecasting then.

Senator Inhofe. You were writing books in 1978?

Mr. Armstrong. Well, I have been in this field for 48 years now.

Senator Inhofe. Wow. I thought maybe I heard wrong. You are the forecasting expert, I recognize that.

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Written by climatebet

February 6, 2008 at 1:10 pm

Armstrong presents testimony at the US Senate Committee on Environment and Public Works

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On January 30, 2008, Scott Armstrong gave a talk presenting his findings to the US Senate Committee on Environment and Public Works’ “Examining Threats and Protections for the Polar Bear”. Click here for full text of the talk. The following are selected excerpts. Full text is available of the paper “Polar Bear Population Forecasts: A Public Policy Forecasting Audit” by Armstrong, Green, and Soon.

We conducted forecasting audits of two of the nine administrative reports that were prepared in 2007 to “…Support U.S. Fish and Wildlife Service Polar Bear Listing Decision.” We selected the reports Amstrup et al. and Hunter et al. as they appeared to be the primary forecasting documents. Our concern was to establish whether the reports’ forecasts of the polar bear population over the balance of the 21st Century were the product of scientific procedures.
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Written by climatebet

January 31, 2008 at 3:53 pm

Anchorage Daily News: Lacking studies, state still disputes polar bear ‘doom’

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Ken Taylor has had easier jobs than this one. It’s not like the good old days chasing rhinos, climbing into bear dens and wrestling beluga whales in shallow water.

Click to enlarge

These days, sitting at a desk as deputy commissioner of fish and game, the veteran wildlife biologist has to muster the best science he can find to argue that Alaska’s polar bears are in good shape and need no special protection from hypothetical doomsday scenarios.

This requires Taylor to stand up to the prevailing wisdom about global warming in most of the world’s scientific community and the public — not to mention some pretty strong opinions in his own department.

But Taylor, the Palin administration’s point man on polar bears, argues that the scientific justification simply isn’t there — at least not yet — to declare the polar bear “threatened” and touch off a cascade of effects under the Endangered Species Act. A decision on the bears is expected from the U.S. Department of the Interior in the next few weeks.

“From my perspective, it’s very difficult to put a population on the list that’s healthy, based on a projection 45 years into the future,” Taylor says. “That’s really stretching scientific credibility.”

The state also pokes at studies used to predict the future of polar ice, quoting at length from the climate scientists’ own demurrals about margins of error. The chain of predicted problems following from those studies are based on “unsupported conjecture,” the state says.

The state’s critique was based on the work of a consultant, J. Scott Armstrong, a University of Pennsylvania expert on mathematical forecasting who has elsewhere challenged former vice president Al Gore to a $10,000 bet on whether the globe is truly warming.

Written by climatebet

January 27, 2008 at 5:16 pm