The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable are defined as climate extremes by Intergovernmental Panel on Climate Change (IPCC). The definition of climate extreme will vary from place to place in an absolute sense (e.g., a hot day in the tropics will be a different temperature than a hot day in the mid-latitudes), and possibly in time given some adaptation from society. By definition, it can be seen that climate extremes can be defined quantitatively in two ways: 1) Related to their probability of occurrence, which can either be expressed with respect to given percentiles of the distribution functions of the variables, and 2) Related to a specific (possibly impact-related) threshold or with respect to specific return frequencies (e.g., 100-year event) (IPCC 2012).
Sindh lies between latitude 23.5° N – 28.5° N and longitude 66.5°E - 71.1°E. It is bounded on the west by the Kirthar Mountains, to the north by the Punjab plains, to the east by the Thar desert and to the south by the Arabian Sea (Indian Ocean) and in the center fertile land around Indus river. The Indus river is the source of water for the agriculture lands. Cotton, wheat and sugar cane are grown on the left bank of the Indus and rice, wheat and gram on the right bank (Chaudhry and Rasul, 2004). Cotton is the cash crop of the country. The climate in Sindh is arid and subtropical with less than 250 mm annual rainfall. The temperature frequently exceeds 45°C in summer (May-September) and the minimum average temperature recorded during winter (December- January) is 2°C. Table 1 shows the mean monthly climatic characteristics of the region from 1980- 2010. Sindh is considered as one of the most vulnerable regions in Pakistan Sindh because of its exposure to the frequent and intense climate extremes in the recent decades (Zahid and Rasul, 2010, 2012; Rasul et al., 2012). This region is facing several challenges listed below due to climate change.
Table 1 Monthly mean climatic characteristics of all the nine stations from1980-2010
Chaudhry, Q.Z. and Rasul, G.: Agro-climmatic classification of Pakistan, Q. Sci. Vis., 9(12), 12 3–4, 2004.
IPCC: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, edited by C. B. Field, V. Barros, T. F. Stocker, and Q. Dahe, Cambridge University Press, Cambridge., 2012.
Pakistan Meteorological Department, Monthly Climatic Normal of Pakistan (1980-2010), Climate Data Processing Centre (CDPC), Karachi, 2013.
Rasul, G., Mahmood, A., Sadiq, A. and Khan, S. I.: Vulnerability of the Indus Delta to Climate Change in Pakistan, Pakistan J. Meteorol., 8(16), 2012.
Rasul, G., Afzal, M., Zahid, M., Ahsan, S. and Bukhari, A.: Climate Change in Pakistan Focused on Sindh Province., 2012.
Zahid, M. and Rasul, G.: Rise in Summer Heat Index over Pakistan, Pakistan J. Meteorol., 6(12), 2010.
Zahid, M. and Rasul, G.: Changing trends of thermal extremes in Pakistan, Climatic Change, doi:10.1007/s10584- 9 011-0390-4, 2012.