Changes and patterns in biologically relevant temperatures in Europe 1941-2000

We took daily near-surface air temperature data from across Europe to calculate a series of 12 biologically relevant temperature summaries. Mean values for two 30 yr periods, 1941–1970 and 1971–2000, were compared and rates of change calculated for those meteorological stations with sufficient data. We generated contour maps for these temperature summaries for both 30 yr periods and for the difference between them; we believe these are the first such maps for over a century. Change was most pronounced and most consistent in those variables describing the onset of spring. Between 1971 and 2000, the thermal start of the growing season began on average 0.36 d yr–1 earlier and ended 0.10 d yr–1 later, suggesting an 11 d earlier beginning and 3 d later end of the growing season over the 30 yr period. For all but one of the temperature summaries, change has accelerated in recent time; however, change was not uniform across Europe.