J5.1
Write-up of Debate
D. Enfield, R. Livezey, J. Knaff,
Debate Moderator: David B. Enfield, NOAA/AOML, Miami, FL
Skillful Forecasts Case: Robert E. Livezey, NOAA/NWS, Washington, DC
No-Skill in Forecasts Case: John Knaff, CIRA, Colorado State Univ., Fort Collins, CO
The question of whether ENSO forecasts have become useful to our society has not been adequately probed. One may encounter opinions as varied as the backgrounds and approaches of the scientists in the climate research community and the stakeholders who use the predictions. Approaching the subject is made difficult by several aspects of the problem: (1) Both the scientific community and the general public (through the lens of the media) with their uniquely different perspectives are involved in the discussion. (2) A climate forecast that ultimately reaches stakeholders is comprised of several tiers, from the coupled model prediction of future SST in the equatorial Pacific to a value-added statistical forecast of the expected land-climate anomalies, to the activity-oriented impacts for society. And (3) the reference by which forecast skill (or success) is measured is a moving target that varies from one investigator to another and from one prediction tier to another.
Let us take the 1997-98 El Nino event as an example. A perusal of media coverage will likely yield the conclusion that the National Weather Service's June 1997 climate outlook bulletin, which urgently warned of a severe winter on the U.S. west coast and southern states, was subsequently proven accurate and that societal benefits ensued as a result. But, to what extent was that outlook, and the decision to make it public with that particular tone, the result of coupled model predictions of equatorial Pacific SST? Alternatively, to what extent was it due to the fact that real-time satellite and in situ observations had already detected a sharp warming off Peru and Ecuador with alarming intensity and geographical scope? In the eyes of many, the question of whether coupled models successfully predicted the El Nino event in the Pacific has become confused with the question of whether the public was provided with an accurate and useful climate outlook for the United States. Here, we have the opportunity to discriminate between these separate questions and focus on the one more appropriate to the conference:
are the numerical and statistical models used to redict equatorial Pacific SST months to seasons in advance skillful?
This debate will start with two successive expositions, for and against, by our designated proponents. Following a short introduction by the moderator, each speaker will have 20 minutes to make his case on this more narrowly defined issue, followed by 20 minutes for a moderated exchange of points and counterpoints, plus an additional 30 minutes including questions and commentary from the audience. The proponents are encouraged to show visuals to illustrate their points. They should take care to define their basis, or reference for measuring skill (e.g., persistence, climatology, etc.) and if possible, specify how the skill changes from one basis to another. In addition, they may wish to argue in favor of one skill reference over another, a related aspect that the community should perhaps consider. In the later stages of general discussion, the moderator may wish to explore some of the wider questions, such as whether the model forecasts have been useful for the anticipation of societal impacts.
Joint Session 5, Debate: "Is There Skill in Forecasting El Nino and La Nina Events?" (Joint with the 24th Conference on Hurricanes and Tropical Meteorology and the 10th Conference on Interaction of the Sea and Atmosphere)
Thursday, 25 May 2000, 8:00 AM-8:15 AM