GUWAHATI, April 28 - Northeast India has ‘warmed’ significantly during the last decade. The rise in surface air temperature in the region has been primarily due to rapid increase in both the maximum (day) as well as minimum (night) temperatures, with the minimum temperature increasing more rapidly.
This is the observation made by Dr Rahul Mahanta, Coordinator of the Interdisciplinary Climate Research Centre, Cotton University (ICRCCU). Dr Mahanta is a leading researcher on various aspects of climate change.
Talking to this newspaper, Dr Mahanta said in the entire northeastern region, a steady warming trend has been observed in the maximum temperature in the post-monsoon months (October to January) and monsoon months (June to September). An increase in the maximum temperature of around 0.4 degree Celsius (C) is notable over the region during the post-monsoon during the last decade with respect to the first decade, considering the normal value during the past century.
Again, he said, the trend in the minimum temperature anomaly is different from that in the maximum temperature. A well marked warming trend is observed in the minimum temperature in all the three seasons – monsoon, pre-monsoon and post-monsoon. The spatial pattern of minimum temperature trend shows an increase all over the region. Parts of Assam, Meghalaya, Arunachal Pradesh and Sikkim experience an increase in minimum temperature of 2 degree centigrade per 100 years over the South Assam meteorological subdivision, he said.
Moreover, he said, quartile-based index for rainfall extremes for the region shows that the probability of extreme monsoon deficiency is generally increasing in Northeast India. Rainfall recession was found occurring leading to an increase in deficient monsoon years in the region. The recession was relatively strong in South Assam, a region of usual maximum monsoon rainfall.
During monsoon months, the adverse impact of drought condition is minimal as the deficiency in monsoon season rainfall is never below 95 per cent of the normal rainfall. An analysis carried out to detect regional trends of the severity of meteorological droughts and floods in Northeast India over the period 1871-2005, showed that the probabilities of moderate droughts were frequent in almost all parts of the region. Drought probability was high particularly in North Assam subdivision, said Dr Mahanta.
Also, the percentile-based index for extreme rainfall events indicates that rainfall extremes are indeed changing in most stations in the region. However, the changes are irregular and location specific. Frequencies of intense rainfall were, however, lowest since the 1990s. ‘Intense’ events occurred in all the observation stations of the region, but very few of them occurred in stations like Guwahati, Imphal and Tezpur.