%X We evaluate the contribution of natural variability to the modern decrease in foraminiferal ?18O by relying on a 2200-yr-long, high-resolution record of oxygen isotopic ratio from a Central Mediterranean sediment core. Pre-industrial values are used to train and test two sets of algorithms that are able to forecast the natural variability in ?18O over the last 150 yr. These algorithms are based on autoregressive models and neural networks, respectively; they are applied separately to each of the ?18O series' significant variability components, rather than to the complete series. The separate components are extracted by singular-spectrum analysis and have narrow-band spectral content, which reduces the forecast error. By comparing the sum of the predicted low-frequency components to its actual values during the Industrial Era, we deduce that the natural contribution to these components of the modern ?18O variation decreased gradually, until it reached roughly 40%, as early as the end of the 1970s.
%D 2012
%L eprints2362
%A Silvia Alessio
%A Gianna Vivaldo
%A Carla Taricco
%A Michael Ghil
%N 2
%J Climate of the Past 
%R doi:10.5194/cp-8-831-2012
%P 831-839
%T Natural variability and anthropogenic effects in a Central Mediterranean core
%V 8
%I European Geosciences Union