By the turn of the century, global warming could radically alter the climatic anatomy of one of the world's most populated river basins — the Indus — thereby impacting millions of livelihoods, says a new study.

The 1.1 million sq. km basin, shared by India, Pakistan, Afghanistan and China, is projected to warm “significantly and progressively”, with average temperatures set to increase by around 4 degrees C by 2080, says a paper published recently in the journal Climate Dynamics.

Warmer winters in the plains, quicker snow melt in the basin's northern highlands (comprising parts of the Hindu Kush, Karakorum, and Himalayas) and more frequent flash floods at the foothills are predicted over the next seven decades, altering the basin’s hydrology, the paper warns.

Winter in the Indus basin on average could be warmer by 3.9 to 5.1 degrees C, and summers by 3.4 to 4.6 degrees C, the researchers found; they created three projections of climate change between 2020 and 2080.

Two simulations indicate a 4 to 8 degree C rise in maximum summer temperature. The summer monsoon is likely to be warmer too, with a rise in maximum mean temperature by 1.5 degrees C by the 2020s. 

By 2080, the number of rainy days over the basin will increase and the intensity of rainfall is likely to rise in the foothills of the Hindukush and other highlands — an area that is already prone to flash floods. Northern highlands could get hotter, and snow and glacier melt likely to hasten. “… The projected changes in extreme events are likely to exacerbate the flood and flash flood hazard,” says the paper.

However, changes in climate are not spatially uniform across the basin. For instance, a decrease in rainfall during winter is projected for 2020 in the southern plains of the basin, but an increase is expected in the upper highlands.

“Overall the projected regional rainfall changes are broadly consistent with the general observation predicted by IPCC in 2007” — “the wet getting wetter and the dry becoming drier.

“'The most affected will be people with least adaptation capacity. Farmers may be left with no choice but to change their cropping patterns, perhaps even their crops,” said Ashwini Kulkarni of the Indian Institute of Tropical Meteorology, and a co-author.