Research Article A Significant Population Signal in Iranian Temperature Records Shouraseni Sen Roy, 1 Mohammad Sadegh Keikhosravi Kiany, 2 and Robert C. Balling 3 1 Department of Geography and Regional Studies, University of Miami, Coral Gables, FL, USA 2 Faculty of Geographical Sciences and Planning, University of Isfahan, Isfahan, Iran 3 School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ, USA Correspondence should be addressed to Shouraseni Sen Roy; ssr@miami.edu Received 28 March 2016; Accepted 11 August 2016 Academic Editor: Panagiotis Nastos Copyright © 2016 Shouraseni Sen Roy et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We assembled daily maximum and minimum temperature records for 31 stations throughout Iran over the period 1961–2010. As with many other areas of the world, we found that both the maximum and minimum temperatures were increasing overall with the minimum temperatures increasing twice as fast as the maximum temperatures. We gathered population data for the stations near the beginning and end of the temperature records and found in all seasons and for both the maximum and minimum temperatures the magnitude of population growth positively infuenced the temperature trends. However, unlike so many other studies, we found the strongest population growth signal in the winter for the maximum temperatures. We found evidence that this winter-season population-temperature signal is related snow cover. Our results illustrate that any number of processes are involved in explaining trends in historical maximum and minimum temperature records. 1. Introduction According to the latest report of the Intergovernmental Panel on Climate Change (IPCC), it has been widely validated that the lower troposphere has experienced warming over the past 50 to 100 years, with substantial decadal and interannual variability. Specifcally, the average global linear trends for combined land and ocean surface temperatures have increased by 0.85 [0.65 to 1.06] ∘ C between 1880 and 2012. In one of the frst and most comprehensive studies at the global scale focusing on the spatial patterns of maximum, minimum, and diurnal temperature range (DTR), Vose et al. [1] showed a declining trend in DTR. Tis declining trend in DTR was attributed to the more rapid rate of increase in minimum temperatures when compared to maximum temperatures. Tis was further validated by a recent study by Donat et al. [2] involving the analysis of HADEX2 dataset, who found signifcant decreasing trends in DTR in more than half of the land areas; only 10% of the land area showed signifcant increases in DTR since 1951. Some of the physical processes attributed to the declining rates in DTR include the efect of clouds, along with the damping efect of precipitation and soil moisture, which can cause a 25–50% decrease in DTR compared to clear sky days [3]. Furthermore, the results of empirical analyses suggest the intensifcation of the hydrologic cycle, such as the increase in trends in frequency and intensity of tropical storms, foods, and droughts. Tis has also resulted in the amplifcation of the warming efect of water vapor in the atmosphere [4]. However, snow cover during winter season diminished the infuence of changes in solar radiation and soil moisture in the mid latitudes [5]. Furthermore, a recent study by Revadekar et al. [6] showed an increasing trend in DTR for high altitude stations located in South Asia, while a decreasing trend was observed in the low altitude stations. Te increasing trends in DTR in high altitude locations were mainly attributed to local level processes. In this context, one of the main driving forces for the increasing trends in land surface temperatures is the function of land use land cover change (LULCC) and urban heat island (UHI) related processes. Te role of urbanization, with more than half of global population living in urban areas, has been identifed as one of the most important factors for higher temperatures. It is important to take into consideration the Hindawi Publishing Corporation International Journal of Atmospheric Sciences Volume 2016, Article ID 1603693, 7 pages http://dx.doi.org/10.1155/2016/1603693