The analysis on surface air temperatures is made using gridded monthly temperature data for the period 1901-2010.
1. Annual mean, maximum and minimum temperatures averaged over the country as a whole showed significant warming trend of 0.60, 1.0 and 0.18 °C per 100
years respectively. The rate of warming trend in the annual mean temperatures since 1980s is much sharper, 0.2 °C per decade.
- 2. On the seasonal scale, the highest increasing trend is observed in the post-monsoon and winter seasons. Monsoon season shows the lowest increasing trend.
- 3. The warming is mostly confined to the northern, central and eastern/northeastern parts of the country. Peninsular India experienced the least warming.
- 4. The warming trend is observed in upper air temperatures also with significant warming trends at the lower tropospheric levels, viz. 850 hPa (1.5 km) and 700 hPa (3.1 km) levels.
Extreme Rainfall and Rainstorms
The analysis on extreme rainfall is made using daily gridded rainfall data for the
period 1901-2010 and rainstorms based on daily gridded data for the period 19512015.
- 1. Frequency of very light rain and light to moderate rain events during the monsoon season has decreased over most of the country.
- 2. However, frequency of very heavy and extreme rainfall events over northern parts of the country has increased significantly. They also show multi-decadal variability, possibly associated with the tropical oceans, especially the equatorial Indian Ocean.
- 3. During the period, 1901-2010, heavy rainfall events (rainfall exceeding 15 cm in 24 hours) over northern parts of the country show an increasing trend of about 6 % per decade.
- 4. Frequency of rainstorms (weather systems with potential of causing large scale floods) has shown an increasing trend of 4 rainstorms in 65 years (1951-2015). Duration of rainstorms has shown a substantial increase of about 15 days during the same period.