Mild winter and spring 2007 over western Europe led to a widespread early vegetation onset

Europe has experienced a wide scale warming over the past decades and climate simulations predict further warming and changes in precipitation patterns during the 21st century. The winter of 2006-2007 has been exceptionally mild with averaged temperatures that may become the norm during the second half of the 21st century. Here we report on satellite observations of the vegetation greening that occurred at the subcontinent scale almost 10 days earlier than the average over the past three decades. Even at the relatively coarse resolution of the satellite data, which mixes several vegetation types, there is a strong negative temporal correlation between the February-April mean temperature and the start of growth date. The western Europe mean vegetation onset sensitivity is -3.9 days per degree of temperature, and is mainly driven by crops and grasslands, with a biome-specific sensitivity of -4.7 days/degrees C. For forested biomes, onset anomalies are better correlated to the March-May mean temperature, with a sensitivity of -3.6 days/degrees C. Based upon the satellite data, there is no consistent indication that a lack of cold days in the winter 2006-2007 had any effect in delaying the vegetation onset.