Quantifying Sources of Uncertainty in Temperature and Precipitation Projections over Different Parts of Europe

Abstract

In this study, uncertainties emerging from natural climate variability, the description of physical processes in models and future anthropogenic activity are quantified for mean temperature and precipitation projections over various regions in Europe. Results of global climate models from CMIP3 dataset were used for 1951–2100 with SRES emission scenarios over the twenty-first century. We are concentrating on three main issues: (1) fractions of total uncertainty and its seasonal variation over the Carpathian Basin, Northern and Southern Europe; (2) limitations in theoretically reducible uncertainty through model development; (3) quantifying the ratio of projected change and total uncertainty (signal-to-noise ratio, when results are significant) and time horizons when changes exceed natural variability (time of emergence, when major impacts happen more likely). Internal variability is the dominant uncertainty factor for the Carpathian Basin, especially in winter due to the intensive circulation activity. Scenario uncertainty has lower impact for the Carpathian Basin than for Northern and Southern Europe, where it has importance for temperature results in the second half of the century. For precipitation, emission scenarios are less meaningful. Fraction of model uncertainty is continuously growing by 2100, especially for precipitation. The smaller the area, the later the mean temperature change surpasses total uncertainty. Signal-to-noise ratio is not significant for precipitation projections over Southern Europe and Carpathian Basin, and over Northern Europe it is only for winter and spring. Seasonal temperature changes exceed natural variability between 2020 and 2045 for the Carpathian Basin, and one-two decades earlier over Northern and Southern Europe. Precipitation projections do not emerge from natural variability over the Carpathian Basin; they do only in summer over Southern Europe, and all the other seasons over Northern Europe by the end of the century.