Abstract
Annual temperature data from thirty meteorological stations in Pakistan’s major urban areas were selected to investigate trends in annual average and maximum temperature during 1970–2009. A combination of parametric and non-parametric tests including linear regression, the Mann-Kendall trend test and Sen’s slope estimator was used for the analysis. Annual average and maximum temperature series showed an overall increasing trend for 90% of the stations and a decreasing trend for 10% of the stations in the study area. The highest significant increment of annual average temperature was observed at Gilgit, Hyderabad, Quetta and Lasbela stations at the rate of 0.49 °C per decade. The highest increment of annual maximum temperature was obtained at Chitral, Gilgit, Nawabshah and Quetta at the rate of 0.31 °C per decade. According to simple linear regression and the Mann-Kendall test, the annual average temperature showed a significant increasing trend for 43% of the stations (at a 0.001 level of significance) and 23% of the stations (at the 0.05 level). Annual maximum temperature showed a significant increasing trend for 26% of the stations (at the 0.001 level of significance) and 23% of the stations (at the 0.05 level). In general, the results showed increasing trends for the considered parameters, although annual average temperature showed a higher increasing rate than annual maximum temperature during the study period.
Highlights
Since the 1950’s, a continuous increase in carbon dioxide, associated radioactive gases and related anthropogenic activities has been documented, and future changes in climate are anticipated [1,2].Climate change is the detection of persistent or extended variability of mean properties caused by natural variability or human activities [3]
Mann-Kendall statistic (Z) values for annual average and maximum temperature were plotted for observational analysis as shown in Figures 3 and 4; the significance of the temperature trend is represented by values with asterisks
The derived results of the present study indicated that warming in the urban areas was caused by increasing annual average temperature rather than annual maximum temperature
Summary
Since the 1950’s, a continuous increase in carbon dioxide, associated radioactive gases and related anthropogenic activities has been documented, and future changes in climate are anticipated [1,2]. Climate change is the detection of persistent or extended variability of mean properties caused by natural variability or human activities [3]. The global meteorological data show overall warming trends with different spatial and temporal variations depending on local climatic regimes [1,4]. According to the Fourth Assessment Report of the International Panel on Climate Change [5], the global average surface temperature rose by 0.74 ◦ C during the twentieth century. The global average surface temperature is predicted to rise by 1.8–4.0 ◦ C and expected to reach The recent five decade warming rate of 0.13 ± 0.03 ◦ C/decade is almost twice that of last ten decades (0.07 ± 0.02 ◦ C/decade).
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