Paleoclimate Reconstructions
Proxy Signal of Past explosive Volcanism
Mid-High Latitudes
e.g. Briffa et al. 1998
Tropical
e.g. Crowley et al. 1997
Tree Ring series from high-latitudes
Vs
Series from the tropics.
What could be the problem? Large influence of ENSO combined with localized measures of a phenomenon that might be only showing up in large scale averages as is available from the models.