KARACHI: During the last century, the average temperature in Pakistan has increased by 0.6°C, which is in conformity with the increase in average global temperature. The temperature rise has affected water and agriculture sources. The mean annual temperature has increased over Pakistan in the recent past with a greater increase in Sindh and Balochistan, according to newly launched Economic Survey of Pakistan 2018-19.
The observed increase is higher in winter when compared with summer. The month wise analysis shows that the maximum increase has been observed in December and February. Similarly, mean annual precipitation has also shown an increase over most parts of the country. The increase is higher in summer as compared to winter with September and June showing the greatest increase. Future climate change projections based on all the four IPCC-AR5 RCPs scenarios show that the average rise in temperature over Pakistan by the end of the century will be about 1°C higher compared to the global average.
Within the country, the northern regions will experience relatively more warming than the south. This increase particularly in temperature is associated with a number of adverse impacts, including the increasing frequency of extreme events (floods, droughts, heat waves, and cyclonic activity), steady regression of most glaciers (except a small minority in the Karakorum Range) that supply the bulk of the country’s water supply and changes in the rainfall patterns.
Impacts of Climate Change on Water Resources The primary effect of climate change is the disruption of the water cycle and it is important to understand the impact that climate change is having on drinking water supplies, sanitation, and food.
In many regions around the world, the incidence of hydrological extreme events is rising day by day. However, in Pakistan it is in many different forms, especially flash flooding in mountainous streams in the north. Analysis of the available long-term record (1969-2014) of annual total flow volumes and annual maximum flows of the Indus River at Besham Qila (a flow gauging station upstream of Tarbela dam), shows no statistical evidence of a significant and sustained change in the aggregate average annual flows in the upper Indus Basin (UIB) upstream of Tarbela Dam.
However, there is a significant increase in the annual maximum flows. This has especially been found in the water availability analysis of the Kabul River Basin, a snowmelt-fed basin, where there is a sharper peak with a clear shift in the annual peak flow by a month.
Also, more increased frequency of larger magnitude annual maximum flow events has come out as a key finding of this Kabul River Basin study. Another modeling work focused on the Gilgit River Basin, a glacier-fed basin, revealed that faster melting of glaciers under increased temperatures would bring more flows a month earlier but with a flattened peak. More rigorous modeling analysis is currently going on to gain a more clear insight into the state and fate of Karakoram glaciers and associated impacts on the river flow regimes in Pakistan.
IMPACTS OF CLIMATE CHANGE ON AGRICULTURE:
Agriculture is one of the major sectors likely to be adversely affected by climate change. Climate change can disrupt food availability, reduce access to food, and affect food quality. Projected increases in temperatures, changes in precipitation patterns, changes in extreme weather events, and reductions in water availability may all result in reduced agricultural productivity.
Crop simulation models-based studies depicted significant reductions in wheat and rice yields in the arid, semi-arid and rain-fed areas of Pakistan under various IPCC climate change scenarios. In general, the increase in temperature leads to a shortening of the Growing Season Length (GSL) for wheat and rice crops in all regions of the country. The studies further report that the South Eastern side of Pakistan is more vulnerable to consecutive heat days stress during flowering and ripening stages of wheat.
This vulnerability is increasing both spatially and temporally to all the major wheat producing zones from Lower Sindh to Potohar till the end of the 21st century under both Representative Concentration Pathways (RCPs i.e. RCP 4.5 and RCP 8.5). In the absence of a change in management practices and technology, an overall reduction will be registered for all cereal crop yields.