Representing two centuries of past and future climate for assessing risks to biodiversity in Europe

Aim: Environmental changes may have important implications for biodiversity in Europe. This study aimed to provide quantification of changes in regional climate during the 20th century and provide scenarios of future changes in CO₂ concentration and climate for the 21 st century as an input to models used to study risks to biodiversity in the EU-funded ALARM project. Location: Europe. Methods: Monthly time series of eight climate variables (maximum, mean and minimum temperature, precidentation, cloudiness, humidity, growing degree days and evapotranspiration) interpolated a regular 10' grid, and of global atmo应pheric CO₂ concentration were constructed for the period 1901-2100. These combine observations from the 20th century with model projections for the 21st century. Projections were selected to capture a range of both climate model and SRES (Special Report on Emissions Scenarios) emissions uncertainties. Results: Averaged over Europe, the scenarios describe changes in mean annual temperature by the end of the 21st century relative to 1961-90 that range between 3.0 and 6.1 °C. Annual precipitation is projected to increase in nothern Europe (+5 to +13%) and decrease in southern Europe (-17 to -7%). An additional scenario describing the collapse of the North Atlantic thermohaline circulation exhibits a sharp cooling over much of Europe and a drying in most seasons. Main conclusions: The climate scenarios presented are consistent with socio-economic storylines developed in parallel, and include a high-emissions case, CO₂ stabilization and a high-impact 'surprise' scenario, involving the collapse of the North Atlantic thermohaline circulation. The embrace a number of key climate and related variables required for studying the impacts of climate change, offer continental coverage and capture a range of uncertainties in future European dimate that are also consistent with the most recent climate projections assessed by the Intergovernmental Panel on Climate Change. The scenarios have already been applied in numerous studues of the impacts of dimate change on biodiversity, some reported in this special issue.