[1] A comprehensive intercomparison of historical wind speed trends over the contiguous United States is presented based on two observational data sets, four reanalysis data sets, and output from two regional climate models (RCMs). This research thus contributes to detection, quantification, and attribution of temporal trends in wind speeds within the historical/contemporary climate and provides an evaluation of the RCMs being used to develop future wind speed scenarios. Under the assumption that changes in wind climates are partly driven by variability and evolution of the global climate system, such changes should be manifest in direct observations, reanalysis products, and RCMs. However, there are substantial differences in temporal trends derived from observational wind speed data, reanalysis products, and RCMs. The two observational data sets both exhibit an overwhelming dominance of trends toward declining values of the 50th and 90th percentile and annual mean wind speeds, which is also the case for simulations conducted using MM5 with NCEP-2 boundary conditions. However, converse trends are seen in output from the North American Regional Reanalysis, other global reanalyses (NCEP-1 and ERA-40), and the Regional Spectral Model. Equally, the relationship between changing annual mean wind speed and interannual variability is not consistent among the different data sets. NCEP-1 and NARR exhibit some tendency toward declining (increasing) annual mean wind speeds being associated with decreased (increased) interannual variability, but this is not the case for the other data sets considered. Possible causes of the differences in temporal trends from the eight data sources analyzed are provided. Motivation and Objectives[2] Wind speed time series have been subject to far fewer trend analyses than temperature and precipitation records [Gower, 2002;Keimig and Bradley, 2002;McAvaney et al., 2001;McVicar et al., 2008; Tomasin, 1999, 2003;Pryor and Barthelmie, 2003;Tuller, 2004;Brazdil et al., 2009], in part because of data homogeneity issues [Thomas et al., 2008;Tuller, 2004;DeGaetano, 1998]. However, understanding how evolution of the global climate system has been manifest as changes in near-surface wind regimes in the past and how near-surface wind speed regimes might alter in the future is of great relevance to the insurance industry [Changnon et al., 1999;Thornes, 1991], the construction and maritime industries [Ambrose and Vergun, 1997;Caires and Sterl, 2005;Caires et al., 2006], surface energy balance estimation [Rayner, 2007], the community charged with mitigating coastal erosion [Bijl, 1997;Viles and Goudie, 2003], the agricultural industry [O'Neal et al., 2005], forest and infrastructure protection communities [Jungo et al., 2002], and the burgeoning wind energy industry [Pryor et al., 2006b]. With respect to the latter, it is worth noting that during 2005-2008 over 18,000 MW of wind energy developments came online in the continental United States, increasing installed capacity to over 25 GW (AWEA wind ene...