01166nas a2200181   4500000000100000000000100001008004100002260002100043100001600064700001500080700001600095700001800111245009000129856006100219300001400280490000800294520068200302       2004                            d  cDecember 24, 2001 aP. Tzedakis1 aK. Roucoux1 aL. de Abreu1 aN. Shackleton00aThe Duration of Forest Stages in Southern Europe and Interglacial Climate Variability  uhttp://www.sciencemag.org/content/306/5705/2231.abstract  a2231-22350 v3063 aForaminiferal oxygen isotope and pollen analyses from a deep-sea sequence off southwest Portugal show that the duration of temperate stages on land over the past 350,000 years varied considerably. The record shows forest contractions during intervals of low ice volume, coeval with declines in atmospheric methane, after which tree populations did not always recover. What emerges is that, although the broad timing of interglacials is consistent with orbital theory, their specific duration may be dictated by millennial variability. This complicates the prediction of the natural duration of interglacials, at least until the origin of this climate variability is understood.