Nonlinearity of teleconnections in paleoclimatological data

Teleconnections in the climate system are a central element of internal variability, yet their degree of nonlinearity and long-term properties remain largely unexplored, especially in a paleoclimatological context. In our investigation, we perform a statistical analysis on data from the ModE-RA paleo-reanalysis to assess the spatial structure and nonlinear character of major atmospheric teleconnections over the last five centuries. We employ the mutual information measure, combined with surrogate data methods to detect statistically significant nonlinearities in the two-dimensional system formed by gridded temperature time series and indices of major modes of internal variability. This approach allows us to identify behaviour which may not be captured by linear correlation methods. Attention is also paid to the possibility of regime shifts or changes in large-scale forcings across different periods.