Teleconnections are defined by the American Meteorological Society as:
“1. A linkage between weather changes occurring in widely separated regions of the globe. 2. A significant positive or negative correlation in the fluctuations of a field at widely separated points. Most commonly applied to variability on monthly and longer timescales, the name refers to the fact that such correlations suggest that information is propagating between the distant points through the atmosphere. “
This linkage can be accomplished by alterations of regional tropospheric temperatures which create changes in the large-scale pressure and wind fields, and/or by the advection of material from one region to another (such as from blowing dust or emissions of pollutants that are advected by the wind). The National Research Council report discusses teleconnections as related to radiative forcings.
Two recent papers provide examples of the teleconnection associated with alterations in regional tropospheric temperatures (see Lu, Riyu, and Buwen Dong, 2005. Impact of Atlantic sea surface temperature anomalies on the summer climate in the western North Pacific during 1997-1998. J. Geophys. Res. – Atm., 110, D16102, doi:10.1029/2004JD005676, August 19, 2005, and Wang, D., C. Wang, X. Yang, and J. Lu, 2005. Winter Northern Hemisphere surface air temperature variability associated with the Arctic Oscillation and North Atlantic Oscillation. Geophys. Res. Lett., 32, L16706, doi:10.1029/2005GL022952, August 20, 2005). This work further illustrates the importance of climate patterns in one region affecting the climate elsewhere through alterations in the large-scale pressure field. Work that Chris Castro of our research group has completed has also illustrated how sea surface temperature anomalies in the Pacific Ocean affect the summer rainfall patterns in western North America by teleconnections.
The acceptance of sea surface anomaly patterns as a surface climate forcing that affects the weather at large distances, of course, is an accepted teleconnection effect. Indeed, this teleconnection effect is why there are major global climate anomalies when an El Niño occurs.
The influence of spatially heterogeneous climate forcing by land-use/land-cover change and by aerosol clouds as they produce teleconnections, however, is less accepted by the climate community despite the clear parallel between climate forcing from sea surface temperature anomalies and these forms of climate forcing. Each of these climate forcings is spatially coherent, persist for long time periods, and significantly affect the fluxes of heat, moisture, and momentum into and out of the atmosphere. We discussed the role of spatially focused climate forcings in our July 28th blog “What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures”? The two new papers by Lu and Dong, and by Wang and colleagues clearly show that it is the regional variations of the climate system that exerts a major influence on the weather we experience. The focus of the climate community on global-averaged and zonally-averaged surface and tropospheric temperature changes is a distraction from what the dominant spatial scales of climate forcing are, as exemplified by these two new papers.