Global warming throws monsoon patterns out of gear

WEATHER EXTREMES | UNPREDICTABLE RAIN

- Jayashree Nandi

India’s southwest monsoon, the economic lifeline for nearly half a billion people, is becoming increasingly unpredictable as global warming weakens traditional circulation patterns while the increased moisture due to a warming planet triggers more extreme weather events.

Recent monsoon disasters in Himachal Pradesh, Uttarakhand and Jammu and Kashmir have provided a glimpse of what India faces in coming decades, scientists warn.

The monsoon directly affects 51% of India’s farmed area, accounting for 40% of agricultural production, with 47% of the population dependent on agriculture for livelihood.

To understand how the monsoon has changed, it's essential first to grasp how this weather system normally operates: Following summer heating of the Indian landmass relative to the cooler Indian Ocean to its south, pressure gradients drive winds that carry ocean moisture across India. This system has been a stable feature of South Asian climate for millennia.

Weaker, but wetter

A report by M Rajeevan, former secretary of India’s ministry of earth sciences, and climate scientists Parthasarathi Mukhopadhyay and Arindam Chakraborty found that monsoon circulation has weakened.

But their research also reveals a climatological paradox is taking hold: Even as the monsoon winds weaken, rising temperatures are increasing atmospheric moisture, creating more frequent dry spells alternating with more intense wet spells.