According to the study, northern India may be drying up a distant Pacific phenomenon
Residents of Latur in Maharashtra’s Marathawada region wait for water supply. File | Photo credit: The Hindu
Rising temperatures and falling rainfall caused by a lesser-known oceanic phenomenon are causing climate shifts in several parts of India, says a research study by scientists from the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) released this month.
Also read | A wild El Niño is brewing thanks to record heat in the Pacific
For the analysis, the team divided India into climate types based on temperature and rainfall thresholds.
The study found that in northwestern India, the hot, semi-arid steppe zone increased from 25.7% of the region’s land area in 1951–80 to 33.1% in 1991–2020, while the mild temperate zone shrank from 25.8% to 18.7%. The eastern edge of the steppe zone has moved from western Uttar Pradesh to the eastern part of the state.
In the Northeast, the (warm) tropical savanna zone decreased from 18.4% to 11.8%, while the “temperate” zone increased from 74.8% to 82.5%. Gangetic West Bengal also shifted from savanna to temperate zone.
The authors attribute the changes to a phenomenon in the Pacific Ocean called the “Victoria Mode” (VM). The VM is a recurring pattern of warm and cold surface water in the North Pacific, separate from the more familiar Pacific Decadal Oscillation.
Future concerns
The drying over north India, covering western and eastern Uttar Pradesh, Bihar and Gangetic West Bengal, is attributed to the negative phase of the VM, which they say has reduced the inflow of moisture. The continued shrinkage and eventual disappearance of tropical savanna and temperate zones “will cause numerous problems related to food security and displacement of local populations,” they note in the paper.
In Peninsular India, the hot semi-arid steppe zone has declined from 30.3% of the region’s area in 1951–80 to 16.4% in 1991–2020. Tropical savanna increased from 61.6% to 75.7%. Konkan and Goa, coastal Karnataka and Kerala and Mahe have seen expansion of their tropical monsoon zones, according to an article published in the latest issue of MAUSAM, IMD’s in-house magazine.
While the Indian subcontinent is accustomed to El Niño effects—a warming of the central Pacific and associated with a shrinking southwest monsoon—previous studies found that most VM events were followed by El Niño events. However, the MAUSAM study does not explicitly link VM to El Niño.
The Pacific Decadal Oscillation (PDO) is negatively correlated with Indian monsoon rainfall, such as the El Nino-La Nina cycle. Studies have shown that when the El Niño Southern Oscillation and CHOP are in phase, they reinforce the usual El Niño-monsoon coupling, and when they are out of phase, they offset each other. The globe is currently in the grip of one of the strongest El Niños on record, and this year’s monsoon rainfall in India has decreased by 12%.
The steppe zone is dry – but not a desert – with limited rainfall and an average annual temperature of 18°C or more. In addition to Uttar Pradesh, the paper places West Vidarbha and Marathwada in this class from 1991-2020, when it was previously mostly savannah. Western Saurashtra and Kutch, on the other hand, moved from completely arid to semi-arid. “Temperate” is the milder zone where the coldest month averages between 0°C and 18°C. The tropical savanna is a warm zone with a coldest month of 18 °C or higher and a clear dry season, with rain mainly in the monsoon months.
For this study, the researchers first classified India into climate types and applied them to gridded IMD records in 0.25-degree squares, roughly 25 km across. They repeated this for five 30-year windows, each starting ten years after the last, and watched how the map changed.
To look for the cause, they compared sea surface temperatures in the North Pacific with rainfall over the Northern Plains from 1981 to 2020 and examined how moisture moves in the region.
Published – 24 Oct 2026 22:29 IST