Climate Crisis in North East India

Context 

• According to a recent analysis, the climate of North East India is changing and rainfall patterns over the region in the last century have considerably changed. 

About 

• North-East India normally receives heavy rainfall during the monsoon months (June-September) but its character has been changed now.
• During 18 of the last 19 years (2001-2019), North East India received monsoon rainfall less than normal with an exception of 2007 (110 per cent of normal), according to an IMD report from 2019.
• A research paper published in the journal JGR Atmospheres in 2018 found that the monsoon rainfall in northeast India decreased by 355 mm between 1979 and 2014. 
  • Out of this, 30-50 mm decrease was due to a reduction in local moisture levels.
•  The flood-drought cycle now has begun to happen within a year, especially during the monsoon. 
  • The rains come in quick bursts and flood the region, followed by elongated dry periods that border on drought.

Factor affecting rainfall pattern

• Moisture and Drought:
  • An increase in moisture and the drying up together change the rainfall patterns in unpredictable ways.
• Snowfall and Excessive snowfall in the Eurasian Region:
  • Other climatic factors such as the increased snowfall in the Eurasian region also impact monsoon rainfall in North East India. 
  • Excessive snowfall in Eurasia causes cooling of the atmosphere of the region, which triggers events eventually leading to a weak summer monsoon season there.
• Pacific Decadal Oscillation (PDO):
  • A study in JGR Atmospheres attributed the decrease in rainfall to sea surface temperatures over the subtropical Pacific Ocean, which vary in a cycle and each phase of which lasts a decade. 
    • The peak comes every 20 years and is known as the Pacific Decadal Oscillation (PDO).
  • A Journal of Climate research paper from 2016 also found that PDO is being influenced by global warming as it decreases the difference of temperatures among the layers of the ocean. 
  • The peak of PDO will change from 20 to 12 years, which may have an impact on the monsoon rainfall in North East India.
• Sunspot Epoch:
  • During the monsoon, rainfall patterns in North East India differed significantly from one sunspot epoch to another, suggesting a differential intensification of the seasonal trough of low pressure over the country.
  • Sunspot epochs are alternating periods of increased and decreased activity on the Sun’s surface that influence the climate of Earth.

Impact

• The changing rainfall pattern, especially during the monsoon season, affects the flow of rivers, extent of snow cover and health of mountain springs, which in turn have an impact on livelihoods, especially agriculture and fishing, forest flora growth, animal and bird habitat (and behaviour) and other ecosystem aspects.
  • There is some evidence of the changing course of rivers from several districts in Assam such as Lakhimpur and Dhemaji, where the Subansiri, Dibang (tributaries of Brahmaputra) and Brahmaputra rivers are changing courses in unexpected ways.
• Extreme rainfall events being caused by global warming trigger a cascade of events such as accelerated soil erosion along the hill slopes devoid of forest cover. This increases the surface run-off of rivers and changes their course.

Conclusion

• One cannot be sure about the exact impact of climate change on the rainfall in the region for the lack of data and credible long-term research on the same. 
  • This is because there is no data collection infrastructure. 
• The data that is collected is not of high quality, which means that no fool-proof analysis can be carried out.                 
• The exact impact of climate change in the region can only be known correctly once all other natural and human-made factors have been studied and accounted for. 
  • The residual impact can then be attributed to climate change.

Source: DTE