No Skill Required
it be helpful if we knew when another big El Niño was about to hit so we could
board up the windows, bring in the cat, and cancel our cable television
general circulation modelers seeking to predict future climate, climatologists
worldwide are working on complex predictive models that say when and where the
next El Niño might occur. One small problem: When you make a forecast for an
event that occurs within your lifetime, someone just might hold you accountable.
come Chris Landsea and John Knaff, who, in the Bulletin of the American Meteorological Society, decided to do just
that. They compared the 1997–1998 forecasts produced by 12 different El Niño
models, some dynamical (i.e., expensive) and some statistical (i.e., less
expensive). Their approach? CLImatology and PERsistence (CLIPER), a model that
uses past events (Climatology) and the recent history of the current event
(Persistence) and is commonly used to evaluate tropical cyclone predictions.
a sense, CLIPER is the simplest possible model. Given the data, it's the kind
of model that an undergraduate statistical climatology class could develop
between the end of the football game and the start of the fraternity mixer using
your average home computer.
not a criticism. In fact, Landsea and Knaff argue that if these more
sophisticated forecast models are to have any useful predictive ability (or
"skill") they should, at a minimum, be better than CLIPER.
1 compares what actually happened ("verification") with the 6- to 8-month
advance forecasts of a variety of models (with a few more simple statistical
forecasts thrown into the mix). Some forecast verifications differ since some
models make predictions for slightly different regions of the tropical Pacific.
Figure 1. A
comparison of 12 ENSO forecasts with observations reveals these models to be
did they fare? In a word, terrible, but with varying degrees of terrible-ness.
Note that CLIPER outperforms nearly all of the more "sophisticated"
dynamical models. As the authors point out, national meteorological centers may
do well to note that "the current best tools are the relatively cheap
statistical systems," not the expensive but ineffective dynamical models that
have yet to produce a reliable forecast."
the paper's conclusion, the authors offer a remarkably candid (for science)
is] disturbing that others are using the supposed success in dynamical El Niño
forecasting to support other agendas. As an example, an overview paper by Ledley
et al. (1999) to support the American Geophysical Union's "Position
Statement on Climate Change and Greenhouse Gases" said the following:
"Confidence in [comprehensive coupled] models [for anthropogenic global
warming scenarios] is also gained from their emerging predictive capability. An
example of this capability is the development of a hierarchy of models to study
the El Niño-Southern Oscillation (ENSO) phenomena....These models can predict
the lower frequency responses of the climate system, such as anomalies in
monthly and season averages of the sea surface temperatures in the tropical
the contrary," the authors state, their own results suggest we should have "less
confidence in anthropogenic global warming....The bottom line is that the
successes in ENSO forecasting have been overstated (sometimes drastically) and
misapplied in other arenas."
the end, they report, "There were no models that provided both useful and
skillful forecasts for the entirety of the 1997–98 El Niño. This is a
conclusion that remains unclear to the general meteorological and oceanographic
C.W., and J.A. Knaff., 2000, How much skill was there in forecasting the very
strong 1997-98 El Niño? Bulletin of the
American Meteorological Society, 81,
T.S., et al., 1999, Climate change and greenhouse gases, EOS, Transactions of the American Geophysical Union, 80,
Books: Satanic Praise
to WCR Chief Editor Patrick
J. Michaels, Ph.D., and co-author Robert
C. Balling Jr., Ph.D., a WCR contributing
editor, on a recent review in Nature
of their book, The Satanic Gases: Clearing
the Air About Global Warming.
the Sept. 28 review of the book, which was published May 1 by Cato Institute
Press, Hans von Storch calls the book "well written and easy to read."
he writes, "the authors should be applauded for their bold predictions for the
future, which will be proven right or wrong by the course of history."
is that degree of boldness that unnerves the paradigm-followers Thomas Kuhn
identified in his 1962 classic The
Structure of Scientific Revolutions (see "The
Way Science Works").
these pages for frequent updates of just what course history is taking. What
matters is not whether the authors are accurate to the last detail, but whether
their self-described "mainstream skeptic" viewpoint is in fact right.
climate models are, for the most part, neither.