Abstract
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 influenced 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.
Highlights
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
Some of the physical processes attributed to the declining rates in diurnal temperature range (DTR) include the effect of clouds, along with the damping effect of precipitation and soil moisture, which can cause a 25–50% decrease in DTR compared to clear sky days [3]
We conducted all analyses by season and found little variability in the minimum temperature trends across the four seasons (Figure 2)
Summary
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. While a large literature has evolved over the past century showing that urbanization creates localized warming, especially at night, the extent to which this effect impacts longterm trends in temperature at regional, hemispheric, or even global scales is a matter of some debate In their most recent assessment, IPCC Working Group I scientists [7, page 37] report in the technical summary that “it is unlikely that any uncorrected urban heat island effects and land use change effects have raised the estimated centennial globally averaged land surface air temperature trends by more than 10% of the reported trend. Assessment of the IPCC reports along with the results of dozens of recent papers reinforces the conclusion that urbanization induces a warming signal with the effect being much greater on the minimum temperatures compared to maximum temperatures In this investigation, we focus on minimum and maximum daily temperatures collected throughout Iran over the period 1961–2010. Iran’s population has seen significant changes as a result of varying population policies during different political periods
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