The assessment of change in temperature of the country is very much essential in the global warming context. The availibity of accurate and reliable long term temperature records becomes imperative for the purpose mentioned above. In the partial fulfillment of the need the area-weighted annual temperature time series for Pakistan is prepared for the period 1901 – 2007, by merging the Climate Research Unit (CRU) and Pakistan Meteorological Department (PMD) observed datasets. For this purpose, some statistical analysis has been done on both the datasets to evaluate the agreement between the two datasets. The datasets were found to have correlation of 0.86 for the period 1960 – 2000, besides other similarities of variance, mean, standard deviation etc. After the reconstruction of long term temperature time series spectral analysis has been carried out to identify the variations over the time span in terms of frequency. This analysis revealed that there are inter decadal oscillations of the period of 14 – 50 years and inter annual oscillations of the period 5 – 6 years in the time series. Linear trend analysis showed that there is a clear indication of warming in Pakistan. The increasing rate of temperature has been found to be 0.06°C per decade. Total change in temperature is calculated to be 0.64°C, with warming and cooling episodes in last 127 years.