GUWAHATI, April 12 � The study � �State Level Climate Change Trends In India� � revealed that many Indian states have experienced significant changes in both maximum and minimum temperatures over the last six decades. However, the changes are not equal for all the states, spatially and temporally. Trends in temperatures showed a much higher degree of spatial coherence and statistically significant warming, reflecting increase in both maximum and minimum temperatures.
The study summarized the details of periodic trends during 1951-2010 as significant increasing trends in the mean maximum temperature over all the states in India, except those in the Indo-Gangetic plains wherein spatially coherent decreasing trends were observed in the annual mean maximum temperature. The maximum increase in annual mean maximum temperature was observed in Himachal Pradesh where the rate of change is +0.06 degree Celsius in a year.
Annual mean minimum temperatures have significantly increased in states of northwest, northeast and southeast India, while the extreme northern states have shown decreasing trends. The rate of increase in annual mean minimum temperature is highest in Sikkim (0.07 degree Celsius in a year), while the rate of decrease is highest in Uttarakhand (�0.03 degree Celsius in a year).
Mean temperatures show a significantly increasing trend over all the states, except Chhattisgarh, Haryana, Jammu and Kashmir, Meghalaya, Odisha, Punjab, Uttarakhand and West Bengal. Punjab (�0.01 degree Celsius in a year) has shown significant decreasing trends in mean temperature.
Seasonal climate change trends have shown significant coherent increasing trends in mean maximum temperature in the southern states for all seasons, while the northern states are having mixed trends, both spatially and temporally.
However, states in the Indo-Gangetic plains are having spatially coherent decrease in mean maximum temperature in winter and summer seasons with highest significant decrease in Haryana by �0.03 degree Celsius in year and in Bihar by �0.02 degree Celsius in a year respectively.
While many states have significant spatially coherent increasing trends in mean minimum temperature during winter and post-monsoon seasons, there is spatially coherent decrease in mean minimum temperature in monsoon season in many states in northern and central India.
State-wide monthly climate change trends in mean maximum temperature reveal significant increase in south Indian states in most of the months. Goa and Tamil Nadu in southern India are having highest increase in monthly mean maximum temperature in November (+0.05 degree Celsius in a year) and January (+0.04 degree Celsius in a year) respectively.
While the states in north India are exhibiting mixed trends in maximum temperature, states in the Indo-Gangetic plains are having decrease in mean maximum temperatures in January, February, March, May and June.
Compared to mean minimum temperature trends, a large number of states are exhibiting significantly increasing trends in monthly mean maximum temperature during the monsoon months of June to September.
