North India getting hotter, drier, South wetter: A study of 70-year climate trends uncovers worrying climate shift

The study also found that India’s peninsular region (excluding the Central Deccan Plateau centred around Maharashtra’s Vidarbha and Marathwada regions), on the other hand, has shifted towards the wetter zone, from arid steppe hot to tropical savannah.

Marathwada and west Vidarbha, already ravaged by drought and farmer suicides, have moved into a hotter, drier climate zone.

The study had set out to investigate historical records of shifts in climate zone modulation across Indian meteorological subdivisions, aiming to uncover the underlying drivers and patterns that have shaped India's climate landscape by examining historical data, including meteorological observations, proxy records, and historical accounts.

“Two significant findings came out of this analysis -- over the historical period 1951–2020, the major change in the climate zone is the shift to the drier region, i.e. temperate to arid steppe and hot and tropical Savannah to temperate hot summer for the North West and North East homogeneous regions, respectively. The percentage area transformed to the drier region is nearly 7% in both homogeneous regions. This modulation is mainly associated with the increasing trend in temperature and decreasing trend in rainfall,” the study has noted.

“For the Peninsular India homogeneous region, the climate zones shift towards the wetter zone, from Arid steppe hot to Tropical savannah by 15% due to a mainly increasing trend of rainfall in recent epochs,” the study also noted.

“But interior Maharashtra, including Marathwada and west Vidarbha, which lay mostly in the tropical savannah zone, which is warm throughout the year with a long dry season, but by 1991–2020 they had moved into the hot semi-arid zone, which is hot with low rainfall, a change the authors attribute mainly to rising daytime and night-time temperatures,” lead study author Ananya Karmakar said.

Climate zones are defined by temperature and rainfall, and the researchers redrew India's climate map for successive 30-year periods (epochs), the standard span over which climate is measured, from 1951–1980 to 1991–2020, using IMD's own observations.

The study noted that between 1961–1990, along the coast, the tropical monsoon zone, the country's wettest, with heavy seasonal rain, has extended further across the Konkan, Goa, coastal Karnataka and Kerala.

The spread of the wettest zone along the coast is consistent with a broader pattern in the study, in which rainfall has increased over southern India even as it has declined over the northern plains, resulting in Maharashtra's interior and its coastline changing in opposite directions.

“The current shrinking and expected disappearance of the tropical savannah and temperate climate zone will cause numerous problems related to food safety and local population displacement. This is something that must be taken into account in future socioeconomic development plans for the country. Overall, the results suggest that the increasing influence of the negative phase of the Victoria Mode plays a pivotal role in modulating rainfall variability and driving the expansion of drier climate classes over Northern India. The continued contraction of tropical savannah and temperate climate zones poses serious risks to food security, water resources, and regional livelihoods. These findings underscore the importance of incorporating large-scale climate variability into long-term agricultural planning and climate adaptation strategies in India,” Karmakar noted.