HR: 10:20h
AN: PP52A-01    [Abstracts]
TI: Historical Chronologies of El Nino Events: Comparison With Instrumental and Proxy Data
AU: * Kaplan, A
EM: alexeyk@ldeo.columbia.edu
AF: LDEO of Columbia University, P.O. Box 1000, Palisades, NY 10025, United States
AB: Historical chronologies of El Nino events (by W.Quinn with collaborators and their recent revisions by L.Ortlieb) are trustworthy and very useful for climate research. However, the way they are produced sometimes resembles art, rather than hard quantitative science. W.Quinn presented a general scheme of converting the evidence for synchronous sets of El Nino-suggesting factors into a chronology of events occurrence and intensity. He provided references for these factors, but in most cases did not demonstrate how the intensity was derived from the evidence. His evidence set represents mostly coastal ocean and land impacts, plus a few teleconnection factors. These indicators are quite different from the typical El Nino indices (e.g. NINO3 or SOI) used today for monitoring or prediction. Nevertheless, consistency between Quinn's rating and instrumental indices like NINO3 or SOI is statistically significant; the outliers are usually excused on the grounds that historical and instrumental indices "measure different things". This work attempts to bring Quinn's ratings, Ortlieb's revisions, and the evidence on which they are based, into the context of the instrumental and high-resolution proxy data. New analyses of sea surface temperature, sea level pressure and surface winds based on the marine data, and analyses of air temperature and precipitation from land stations for the last two centuries, along with proxy-based El Nino reconstructions are compared with five centuries of historical chronologies. The instrumental data indices show a remarkable cross-variable agreement, particularly good for strong events. The difference between their consensus and historical chronologies are explained in the context of local coastal versus large-scale climate variability. Connection with proxy-based reconstructions is in general more loose, but seems to be affected by the same factors.
DE: 4522 ENSO (4922)
DE: 4922 El Nino (4522)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly