Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING LIMITED IRRIGATION AND RAINFALL FOR CROP PRODUCTION IN SEMI-ARID ENVIRONMENTS

Location: Wind Erosion and Water Conservation Research

Title: The identification of distinct patterns in California temperature trends

Authors
item Codero, Eugene -
item Kessomkiat, Wittaya -
item Abatzoglou, John -
item Mauget, Steven

Submitted to: Climatic Change
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2010
Publication Date: September 1, 2011
Citation: Codero, E.C., Kessomkiat, W., Abatzoglou, J., Mauget, S.A. 2011. The identification of distinct patterns in California temperature trends. Climatic Change. 108:357-382.

Interpretive Summary: Regional changes in California surface temperatures during 1918-2006 are studied here using weather station data from the US Historical Climate Network and the National Weather Service Cooperative Network. Statistical analyses using annual and seasonal temperature data over the last 80 years show noticeably different patterns in trends derived only from maximum daily temperatures (Tmax) compared to trends derived from minimum temperatures (Tmin). These differences are apparent over various regions of California, and are also evident during different periods of 1918-2006. For trends in average annual temperature computed since 1918, minimum temperatures are warming much faster than maximum temperatures. Since 1970 the overall warming has not only accelerated, but the increases in Tmin and Tmax have also been of similar magnitude. This is especially true in the southern deserts, where warming trends during the spring seasons (March-May) are exceptionally large. While observations show coherent statewide positive trends in Tmin, trends in Tmax tend to vary from region to region, and are also less uniform over time. Although there is a warming trend in mean annual temperatures recent in Southern California, over smaller areas cooling trends are evident during winter and summer. Together, this evidence of varying regional temperature change suggests that more than one climate forcing mechanism must be present to produce these responses.

Technical Abstract: Regional changes in California surface temperatures over the last 80 years are analyzed using station data from the US Historical Climate Network and the National Weather Service Cooperative Network. Statistical analyses using annual and seasonal temperature data over the last 80 years show distinctly different spatial and temporal patterns in trends of maximum temperature (Tmax) compared to trends of minimum temperature (Tmin). For annual trends computed since 1918, Tmin is warming much faster than Tmax. However, since 1970 the warming has not only accelerated, but also the increases in Tmin and Tmax have been of similar magnitude. This is especially true in the southern deserts, where warming trends during spring (March-May) are exceptionally large. While observations show coherent statewide positive trends in Tmin, trends in Tmax tend to vary on finer spatial and temporal scales. Accompanying recent Tmax warming trends in Southern California are regional and local level cooling trends during winter and summer. These signatures of regional temperature change suggest that a collection of different forcing mechanisms or feedback processes must be present to produce these responses.

Last Modified: 9/10/2014
Footer Content Back to Top of Page