Thule Research Seminar "Towards better understanding of Global Change", 12-14 October 2009, Oulanka, Finland

Unravelling long-term behaviour in historic geophysical data sets

Thomas Ulich1 and Tuomo Nygrén2

1Sodankylä Geophysical Observatory, Sodankylä, Finland,
2Space Physics Group, Dept of Physical Sciences, University of Oulu, Oulu, Finland


The change of our environment on long time scales, globally as well as locally, is arguably one of the most important factors in 21st-century politics and policy-making. Today we are looking back at an impressive collection of scientific data about our environment. Most of these data are presented to us as time series. These often historic records of geophysical parameters have been obtained under variable conditions, and often they are not continuous. Moreover, comprehension of these data is made difficult by underlying effects external to the variability to be investigated. For instance temperature records exhibit a seasonal cycle. Thus great care and special tools are required in order to draw valid conclusions from an investigation. Here we show examples of such data sets and discuss how to unravel their long-term behaviour.