Trends and Abrupt Shifts in Mean Temperature over North-East India: Insights from Gridded Datasets

Abstract

Addressing the critical issue of climate change over North-East India (NEI), this study investigates surface temperature trends during 1979–2020, primarily using IMDAA reanalysis data, supplemented by additional high resolution gridded datasets. Temperature trends were assessed on annual, seasonal and monthly scales across administrative divisions of NEI and the agro-climatic zones (ACZs) of the Eastern Himalayan Region (EHR). Mann–Kendall tests were employed to detect monotonic trends, while abrupt climatic shifts were identified using Cumulative Sum charts and homogeneity tests. Findings revealed a general warming pattern over the entire region with significant annual increment of 0.16 °C decade−1. Pronounced warming was observed during the monsoon, post-monsoon and winter seasons, whereas the pre-monsoon season exhibited a lack of statistically significant trends. Warming rates during post-monsoon and winter exceeded ~ 0.2 °C decade−1 across most regions suggesting a shift in seasonal duration and thermal regimes. Change points around 2005 marked 0.5 °C temperature shifts across both NEI and EHR. Temperature anomalies transitioned from negative to positive values around the early twenty-first century, suggesting a clear phase shift in the regional climate. Comparative assessment of gridded datasets (IMDAA, IMD, CRU, ERA5 and ERA5-Land) also revealed significant warming trends across NEI, with Arunachal Pradesh and Sikkim exhibiting the highest increases, giving an indication of Elevation Dependent Warming. This research emphasizes the need for region-specific strategies to mitigate climate change impacts on agricultural, water resources and sustainable development. It offers policy insights and recommends advanced methods for future work, while acknowledging the need to enhance data precision and analytical techniques.

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