A1461
Title: Climate normals and anomalies
Authors: Tommaso Proietti - University of Roma Tor Vergata (Italy) [presenting]
Alessandro Giovannelli - University of L'Aquila (Italy)
Abstract: Studies of interannual climate variability rely on time series of temperatures, sea level, pressure, and rainfall anomalies. Anomalies are what residues after adjusting raw measurements for climate trends and seasonality. The adjustment is made by subtracting the decadal monthly or seasonal averages of the series computed over past reference periods consisting of three decades. Are the methods currently in use suitable? Are they able to capture climate warming trends and changing seasonality? Are traces of unadjusted trends seen in the anomaly series? Are the parametric and nonparametric methods adopted in other areas for similar tasks (seasonal adjustment) in econometrics a realistic alternative for climate time series? Alternative methods based on local polynomial and trigonometric regression can be devised to overcome some of the shortcomings of the methodology currently in use. The relevance of these alternative methods is discussed and evaluated with reference to the ENSO phenomenon.
