  Recent work has provided ample evidence that global climate dynamics at
time-scales between multiple weeks and several years can be severely affected
by the episodic occurrence of both, internal (climatic) and external
(non-climatic) perturbations. Here, we aim to improve our understanding on how
regional to local disruptions of the "normal" state of the global surface air
temperature field affect the corresponding global teleconnectivity structure.
Specifically, we present an approach to quantify teleconnectivity based on
different characteristics of functional climate network analysis. Subsequently,
we apply this framework to study the impacts of different phases of the El
Ni\~no-Southern Oscillation (ENSO) as well as the three largest volcanic
eruptions since the mid 20th century on the dominating spatiotemporal
co-variability patterns of daily surface air temperatures. Our results confirm
the existence of global effects of ENSO which result in episodic breakdowns of
the hierarchical organization of the global temperature field. This is
associated with the emergence of strong teleconnections. At more regional
scales, similar effects are found after major volcanic eruptions. Taken
together, the resulting time-dependent patterns of network connectivity allow a
tracing of the spatial extents of the dominating effects of both types of
climate disruptions. We discuss possible links between these observations and
general aspects of atmospheric circulation.
