Changing trends of thermal extremes in Pakistan

Abstract

Extreme events have gained considerable scientific attention recently due to their potentially catastrophic impacts. Heat waves are thought to be more pronounced now in most parts of the world, and especially in South Asia, but doubts remain. The aim of this study is to calculate the frequency and intensity of heat waves in South Asia, focusing on Pakistan and identifying the regions within Pakistan that are most vulnerable to heat waves. Analyses have been performed both at provincial and country levels from 1961 to 2009. The provincial level analysis shows positive trends for heat waves of magnitudes ≥40°C and ≥45°C for 5 and 7 consecutive days. Events of magnitude ≥40°C and ≥45°C for 10 consecutive days also increased in frequency in Punjab, Sindh, and Balochistan. These regions are therefore considered to be the regions most vulnerable to heat wave events in Pakistan. The Balochistan region shows a consistently increasing trend throughout the study period, which may lead to more frequent drought in the future. The country level analysis indicates an increase in the frequency of 5 and 7 consecutive days heat waves at all defined temperature thresholds. The 10-days heat waves spells show a slight increase at ≥40°C and no significant change at ≥45°C. The Gilgit Baltistan and Azad Jammu & Kashmir areas reported no events at ≥45°C for 5, 7 and 10 continuous days. It is anticipated that with a long term rise in temperatures around the globe, heat waves will become more frequent and intense in all parts of the world, including Pakistan.

Contemporary Temperature Fluctuation in Urban Areas of Pakistan

“…The derived results in the present study are in accordance with Ambreen, Ahmad, Sultan, Sun and Nawaz [23], who specified an isothermal shift and temperature variability in mountainous areas compared with plain areas of Pakistan, as the stations in northern regions and Balochistan province showed a significant increasing temperature trend that depicted the regional warming trend in the northern areas and some hilly areas of Balochistan. Heat wave historical records for Pakistan presented by Zahid and Rasul [21] reported previous events and expected higher intensity heat waves for Sindh and Balochistan. Heat waves have been reported for being responsible for alteration in temperature trends in the Mediterranean region, according to Galdies [41].…”

“…Annual T max also showed a maximum significant trend for the southern part of the country including Balochistan province (Quetta and the surrounding regions such as Sibi and Kalat) Sindh province (Karachi, Badin, Hyderabad, Nawabshah, Khanpur and some regions of Jackobabad) as repeated severe heat wave events [21], desertification and productivity loss [20] have been reported in this part of the country. The Annual T max showed a moderate to increasing trend at Bahawalpur, Multan and Bahawalnagar; whereas other regions including the central part of the country (Lahore, Sialkot, Islamabad, Kotli, Skardu and Peshawar) showed minimum trends.…”

“…Highly significant and increasing trends for annual average and maximum temperature in the northern areas are worrisome for retreating glaciers that feed the Indus River. In the Balochistan province and extreme South, the coastal areas where droughts and severe heat waves are reported frequently, are threatened by further environmental degradation and desertification [21] and such climatic conditions require a great deal of attention [47].…”

“…The lower basin receives mean annual rainfall less than 200 mm, and annual mean temperature ranges between 17 and 28 • C [18]. The province of Balochistan, including regions of Sibi, Panjgur, Lasbela, Pasni, Quetta and Kalat, is characterised by an arid climate that receives the lowest rainfall and is prone to desertification [21].…”

“…These seasonal variations have implications for water resources and food security for the country, as Sultana et al [20] found drastically declined yields due to increasing temperature and CO 2 emissions in arid, semi-arid and sub-humid climatic zones. Concerning global warming and climate change, Zahid and Rasul [21] found a nationwide positive trend for a heat wave of magnitude ≥40 • C and ≥45 • C for 5 and 7 consecutive days, respectively; a heat wave frequency ≥40 • C and ≥45 • C for 10 consecutive days occurred in Punjab, Sindh, and an increasing trend throughout the period was observed in Balochistan. Heat waves prevailing for several days with 5 • C higher temperature than normal were also evident in the Eastern Mediterranean climate according to Kostopoulou and Jones [22].…”