Science Source

Trends in U.S. Surface Humidity, 1930–2010

Examines US hourly surface observations at 145 stations to identify annual and seasonal changes in temperature, dewpoint, relative humidity, and specific humidity since 1930
Finds that average long-term trends (1930–2010) indicate that temperature has warmed but that little change has occurred in dewpoint and specific humidity
Finds that trends since 1947 indicate that the warming of temperatures has coincided with increases in dewpoints and a moistening of specific humidity
Finds that this moistening is especially pronounced during the summer in the Midwest
Finds that for the nation, trends in relative humidity show little change for the period 1947–2010, during which these data are more homogeneous
States that moistening has occurred throughout the central United States while other regions have experienced drying