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

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Summary

Introduction

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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