ASSOCIATIONS BETWEEN TEMPERATURE TRENDS∗

Abstract

ABSTRACT Trends in the average temperature for land surfaces in midlatitudes of the Northern Hemisphere (LMNH) are associated with geographical patterns of long-term temperature variations. Alternating areas with strong positive and negative associations for January suggest systematic changes in advection. The patterns for July and the year are more homogeneous; associations are positive for many of the areas for which data are available. While spatial patterns of long-term temperature trends are coherent, significant changes in associations can occur. Variations in atmospheric circulation patterns have, in some areas, led to changes in the sign of the connection between the LMNH curve and long-term trends in local temperature. Shifts in circulation also have caused parallel temperature trends in adjacent areas to suddenly diverge. Such changes in associations cannot be ignored considering their implications for climatic predictions and the search for teleconnections.