Sound information on future climate change is the key scientific basis for climate risk assessment, development of mitigation/adaptation strategies and, ultimately, for planning and decision making at local to global scales. It became evident only recently that uncertainties of future climate projections can be substantially reduced if the climate models are constrained by high-quality paleoclimate data. Long and annually-resolved proxy time series are the only robust means to assess the direction, magnitude and rates of change for forced and unforced climate variability.

Studying the last 1000 years is critical. These years mark the boundary conditions for our modern climate system, social organisation, biodiversity and economic structure. Reconstructing spatial variations in the climate over the last millennium holds the key for understanding the natural variability of European climate. This information is essential if models predicting the consequences of future climate change are to be realistic. The need for unprecedented quality standards for paleoclimate data was fully recognized by IGBP-PAGES (Science Plan 2008-2011): "further scientific advancement is impeded by the lack of robust, well-calibrated and validated quantitative paleoclimate time series at regional scale and seasonal resolution".

One of the best locations for investigating European climate is north-eastern Poland which explains up to 86% of the variance of winter temperature in Eastern Europe and shows high teleconnectivity to the dominant North Atlantic - European circulation patterns. Thus data from Poland are of first-order significance and of general scientific as well as public interest.

Standardized winter mean temperatures of Poland (black line) and European land areas (excluding Poland, red line) for the last 500 years (Luterbacher et al. 2004). The thick lines denote the 30-yr running means.		Spatial correlation map between winter temperature averaged over Poland and European land areas over the last 500 years (Luterbacher et al. 2004).

Luterbacher J., Dietrich D., Xoplaki E., Grosjean M., .Wanner H., 2004. European seasonal and annual temperature variability, trends, and extremes since 1500. Science 303: 1499-1503.