Pacific ocean cycle is drying parts of north India, says new climate study

A distant Pacific Ocean phenomenon is driving rising temperatures and falling rainfall across several parts of India. Scientists at the India Meteorological Department and the Indian Institute of Tropical Meteorology published these findings in the journal MAUSAM this month.

Climate Shifts

In north-west India, the hot, semi-arid steppe zone grew from 25.7% of the region's area between 1951 and 1980 to 33.1% between 1991 and 2020. The milder temperate zone in the same area shrank from 25.8% to 18.7%, with the steppe zone's eastern edge moving from west Uttar Pradesh to the eastern part of the state. In the north-east, the warm tropical savannah zone fell from 18.4% to 11.8%, while the temperate zone rose from 74.8% to 82.5%. Gangetic West Bengal also shifted from savannah to temperate. Meanwhile, in peninsular India, the hot semi-arid steppe zone dropped from 30.3% to 16.4%, while tropical savannah rose from 61.6% to 75.7%. Konkan, Goa, coastal Karnataka, Kerala, and Mahe saw their tropical monsoon zones expand.

The Victoria Mode

Authors trace these regional changes to the Victoria Mode, a recurring pattern of warm and cool surface water in the North Pacific Ocean that is separate from the Pacific Decadal Oscillation. The negative phase of this pattern reduced moisture flow into northern India, affecting areas like west and east Uttar Pradesh, Bihar, and Gangetic West Bengal. Scientists warn that the continued shrinking of these climate zones can hurt food safety and displace local populations. While El Niño warms the central Pacific and shrinks the southwest monsoon, and the globe faces a strong El Niño that reduced India's monsoon rainfall by 12% this year, the MAUSAM study does not explicitly link the Victoria Mode to El Niño.

Context

Climate zones are classified based on long-term temperature and rainfall thresholds over multi-decade periods. Scientific studies use gridded historical records to track how these regional climate boundaries shift over time in response to changing oceanic and atmospheric conditions.