The report’s authors examined over 9,000 excavated and dated wooden artefacts from the past 2,500 years. They discovered a correlation between extended periods of warm, wet summers and the prosperity of societies. Extended periods of climatic instability coincided with periods of political turmoil and social unrest.

The report presents tree ring–based reconstructions of Central European summer precipitation and temperature variability over the past 2500 years.

The full survey, '2500 Years of European Climate Variability and Human Susceptibility' was published this month by the online journal, Science.