Is northern Europe turning green? An environmental audit of climate change

We combined a phenological model of budburst in birch in northern Europe with three empirically adjusted temperature scenarios for the 21st century and analyzed the resulting budburst projections along a gradient from oceanic to more continental climates. The temperature scenarios were generated by two global medium resolution circulation models (ECHAM4/OPYC3 and HadAM3H) providing the boundary forcing which was input to a regional climate model (HIRHAM), and for two IPCC emission scenarios (A2 and B2). The three scenarios generate surprisingly contrasting regional trends in the phenological response to climate warming. This is due to the scenarios predicting the greatest warming at different times during spring, and the phenological model predicting a lesser sensitivity of phenology to warming in continental climates, where temperatures rise more quickly from winter to spring. This is the first study that projects regional differences in the phenological responses to climate change, explains their causes and assesses the impact of different warming scenarios, raising questions about earlier conclusions based on simplified warming scenarios.