Unprecedented floods in Pakistan have displaced more than 20 million people by inundating more than 50,000 square miles in Khyber Pakhtunkha  and southern plains of Punjab and Sindh provinces. Many independent studies, including the UNDP report of 2009, cautioned that the majority of Pakistan’s 5,218 glaciers (covering an area of 15,000 square kilometres) are moving forward (surging) and producing various geo-hydrological instabilities.

In short, regional climate change is accelerating the melting of these glaciers’ ice and snow, and causing a dramatic increase in melt waters over a short period of time. The ablation zones of glaciers lie in deep and arid valleys of the Karakoram Himalayas and contribute a huge amount of melt water that forms sub-glacial lakes. The build-up of high water pressure causes surging in ice masses and sometimes collapses the ice portal or snout of the glaciers. Such collapses are know as Glacier Lake Outburst Floods (GLOF) and are charged with an enormous amount of debris material.

It appears that the present catastrophic and devastating flooding of the rivers, as in Kabul, Swat and Indus, is caused by the collapse of glacial portals and exceptionally heavy monsoon rains in the upper Indus basin.

The flooding of these regions of Pakistan have been further exacerbated by the silting of major reservoirs, such as Tarbela (on the Indus) and Mangla (on the Jhelum) and many small barrages and reservoirs. Himalayan water has been charged with huge suspended sediment loads over the years — indeed, even in normal times, Pakistan has had problems managing the heavily-silted water flowing in its rivers.

Another factor contributing to Pakistan’s flooding is the increasingly variable summer monsoon pattern. The summer monsoon now brings large rainfall variability, a reduction of the number of rainy days, and an increase in short and intense periods of rainfall. The overall result of the change is that while there is an overall decrease in the amount of rainfall, there is also an increase in both drought and flood conditions. In view of this climatic transformation, the regime of water resources — snow-fed, ice-fed, and rain-fed — in the Himalayas and the Karakoram, is likely to change rapidly in terms of discharge rates, volume and availability.

We now have a better understanding of the rate at which water availability in the ecosystem is changing. Remote sensing and real time data sets are revealing the relative proportions of the different sources of water (namely melting glaciers, snow, and rainfall). It is evident that the changing weather patterns in the northern ecosystem are strongly affected by the influences of climate change.

The observed erratic timing and intensity of the regional monsoon and westerly systems have created serious hazards for Pakistan. Policy makers in the region now have to begin effectively planning adaptation strategies for such extreme weather conditions.

The case is not hopeless. Decision makers can support better regional and global climate analyses and predictions. This requires more ground observation networks and detailed modelling that can help scientists and policy makers better predict extreme weather events. Quantitative projections of the impact of 21st century melt on the region’s future water resources should be established by combining climate model simulations (driven by future scenarios of green house gas and aerosol emissions) with numerical models capable of accurately simulating snow/ice melt and surface hydrology.

NASA’s satellite remote sensing products derive process models for glacier mass balance and surface hydrology and can be instrumental in helping to correctly understand the region’s hydrology. However, NASA’s satellite observations and in-situ forcing of snow/ ice melt modelling must be verified by using real-time data sets collected on benchmark glaciers by Pakistani, Indian, Afghan, and Chinese scientists. The cascading effects of changes in water availability necessitates trans-boundary scientific coordination amongst scientists and policy makers in Afghanistan, Pakistan, India and China.

Only through such coordination can policymakers obtain a holistic perspective of the ongoing changes in the region’s river systems. The critical mass sufficient to characterise the multiple impacts of climate change and communicate to decision makers is woefully lacking in South Asia. Capacity building is therefore a critical issue.

The writer is a senior visiting fellow, Stimson Center, Washington