Surface air temperature variability over India during 1901-2007, and its association with ENSO

Seasonal and annual trends in surface air temperature over India and 7 homogeneous regions (western Himalaya, northwest, north-central, northeast, east coast, west coast and interior peninsula) were assessed during 3 periods: 1901-2007, 1971-2007 and 1998-2007. Indian annual mean (average of maximum and minimum), maximum and minimum temperatures showed significant warming trends of 0.51, 0.72 and 0.27 degrees C 100 yr(-1), respectively, during the period 1901-2007. However, accelerated warming was observed in the recent period 1971-2007, mainly due to intense warming in the recent decade 1998-2007. Temperatures (mean, maximum and minimum) increased by about 0.2 degrees C per decade for the period 1971-2007, with a much steeper increase in minimum temperature than maximum temperature. In the most recent decade, maximum temperature was significantly higher compared to the long-term (1901-2007) mean, with a stagnated trend during this period, whereas minimum temperature showed an increasing trend, almost equal to that observed during 1971-2007. On a seasonal scale, pronounced warming trends in mean temperature were observed in winter and monsoon seasons, and a significant influence of El Nino Southern Oscillation events on temperature anomalies during certain seasons across India was observed. The composites of maximum and minimum temperatures of El Nino years showed positive anomalies during monsoon, post-monsoon and subsequent year winter and pre-monsoon seasons. However, statistically significant positive anomalies were observed only during monsoon and post-monsoon seasons over large areas of the country. The composite temperature anomalies of La Nina years were almost opposite to El Nino composites: the negative temperature anomalies associated with La Nina events persisted from the current monsoon season to the subsequent year pre-monsoon season.