In recent times, an analytical study has spotlighted that North East (NE) India is undergoing altering precipitation patterns due to climate change. This revelation underlines the significance of the National Action Plan on Climate Change (NAPCC), which was instituted in 2008 by the Prime Minister’s Council on Climate Change. The NAPCC features strategies that facilitate the developmental targets of India, while also providing ancillary benefits for effectively tackling climate change.
The Changing Rainfall Pattern in NE India
Typically, NE obtains heavy rainfall during the monsoon months, from June to September. However, alterations have been observed in this pattern in recent years. Heavy rainfall now comes in sudden deluges, causing floods, then followed by extended periods of dry spells, which closely resemble droughts.
In 2018, a research paper revealed that monsoon rainfall in NE had decreased by 355 mm between 1979 and 2014. This decrease, ranging between 30-50 mm, was attributed to a reduction in local moisture levels. Owning to its distinct topology featuring steep slopes transitioning abruptly to plains, NE is susceptible to changes in river courses.
Nestled primarily in hilly terrain and extending the Indo-Gangetic Plains, the region is highly sensitive to shifts in regional and global climatic conditions. The rainy seasons in NE India include the pre-monsoon and monsoon period. It has been noticed that the monsoon rainfall in most NE states has decreased in the past two decades below the Long Period Average (LPA). With the number of rainy days also declining in several districts north of the Brahmaputra, these changes result in heightened flood risks.
Factors Influencing Changes in Rainfall Patterns
Several factors are contributing to this fluctuation in rainfall. One primary element is the interplay between moisture levels and drought frequencies. Due to land warming, the land dries up, causing an increase in the frequency and intensity of dry spells and droughts. Concurrently, an increase in moisture levels also plays a role, both factors together formulating unpredictable rainfall patterns.
Another key determinant is the increased snowfall in the Eurasian region. The excessive snowfall cools the regional atmosphere, triggering events that eventually lead to a weaker summer monsoon season in NE India.
Changes in the Pacific Decadal Oscillation (PDO) also have impacts on the region’s rainfall. PDO is a cyclical variation in sea surface temperatures over the subtropical Pacific Ocean, with each phase lasting approximately a decade. The PDO peaks every 20 years and global warming influences it by reducing the temperature differences among ocean layers.
Significance is also attributed to Sunspot Epochs, which are alternating periods of increased and decreased solar activity impacting Earth’s climate, causing differential rainfall patterns.
Impact of Changing Rainfall Patterns
The shift in rainfall patterns, particularly during the monsoon season, has far-reaching effects on rivers’ flows, snow cover extent, and mountain springs’ health. These changes significantly influence livelihoods, primarily agriculture and fishing, forest flora growth, animal and bird habitats and behaviors, and various other ecosystem aspects. There’s also evidence of rivers like Subansiri, Dibang (tributaries of Brahmaputra) and Brahmaputra altering courses unexpectedly.
Global warming-induced extreme rainfall events lead to consequent occurrences such as accelerated soil erosion along hill slopes devoid of forest cover. This elevation in surface runoff of rivers alters their course drastically, impacting the region’s overall ecology.