What will be the fallout of an India-Pakistan nuclear war?
While jets fall and shells fly across the border, the real cost of the India-Pakistan conflict is borne by regional development, diplomacy, and the long-silenced people of Kashmir
Amid current border tensions and diplomatic standoffs between India and Pakistan, what many people do not realise is how much the whole world would suffer if either country used its nuclear weapons. Behind all the talk of national security and defence, there is a serious and frightening reality: a regional nuclear war between these two countries could turn into a global humanitarian, environmental, and economic catastrophe.
The human crisis
According to a 2019 study published in Science Advances, a full-scale nuclear conflict between India and Pakistan could kill between 50 to 125 million people within just seven days—a death toll that would be even higher than that of the entire Second World War. The scale of destruction would be fuelled by each side's growing nuclear arsenal.
As of recent estimates, India and Pakistan collectively possess between 400 to 500 nuclear weapons, a number projected to increase by 2025. These weapons range from 12 to over 45 kilotons, with some potentially reaching into the hundreds of kilotons.
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Should India strike 100 urban centres with strategic nuclear weapons and Pakistan respond with 150, the immediate human toll would be unparalleled. Cities would be flattened, emergency infrastructure decimated, and millions left to die from blast injuries, radiation, and subsequent health crises.
A climate crisis beyond borders
The devastation would not stop at national borders. The same study highlights the climatic consequences of a regional nuclear war, particularly the phenomenon known as a nuclear winter. The explosion-induced firestorms would emit between 16 to 36 teragrams (Tg) of black carbon smoke, which would rise into the stratosphere and disperse across the globe within weeks.
This thick layer of soot would block 20% to 35% of sunlight, causing global surface temperatures to fall by 2°C to 5°C. Rainfall would decline by 15% to 30%, particularly disrupting the already delicate South Asian monsoon cycle. The cumulative impact would devastate agriculture, affect water availability, and intensify humanitarian crises across regions already vulnerable to climate shocks.
The aftershocks of this environmental catastrophe would persist for more than a decade, with global ecosystems taking years to recover. Net primary productivity—essentially the capacity of ecosystems to support plant and animal life—would decline by 15% to 30% on land and 5% to 15% in oceans, significantly weakening food chains and biodiversity.
Global food supply
The consequences for global agriculture are equally alarming. A 2022 study published in Nature Food found that a nuclear war between India and Pakistan would dramatically impact global food security. Staple crops such as maize and wheat could drop by up to 40% in some key agricultural regions due to reduced sunlight, lower temperatures, and disrupted rainfall patterns.
These agricultural disruptions would not remain localised. With global trade and supply chains tightly interconnected, such a collapse would trigger food shortages and famine far beyond South Asia. Countries with already fragile food systems could face starvation-level emergencies, while even food-secure nations might struggle with price spikes, inflation, and social unrest.
Strategic miscalculation and escalation
While the numbers reveal the physical and environmental cost, such a disaster could also be caused by political miscalculation. Declassified US intelligence reports, shared by the National Security Archive in April 2025, highlight the risk of misinterpretation or irrational decision-making escalating a conventional military skirmish into a nuclear exchange.
Unlike the Cold War-era systems of repression between the US and the Soviet Union, South Asia lacks the communication channels and confidence-building mechanisms. In the event of a high-pressure crisis, a breakdown in diplomacy could result in irreversible decisions being made within minutes.
Tensions over water resources have further complicated this fragile stability. India's recent suspension of the Indus Waters Treaty, a critical bilateral agreement, adds a new dimension to the conflict. With Pakistan heavily reliant on the Indus river system for both agriculture and hydropower, any attempt to restrict access could push Islamabad to respond defensively, potentially with military force.
