Indian States have been gradually registering a withdrawal of spring — a period of relatively benign weather between the winter of January and the scorching summers of April, a 50-year analysis of meteorological records suggests.
Researchers from the agency Climate Trends calculated the monthly average temperature for 33 States and Union Territories from 1970-present. This was the period during which the impact of global warming has been empirically observed and for which consistent data exists.
For each State or territory, the rate of warming for each month was compared to each three-month meteorological season. For instance, December-Jan-February is considered winter in meteorological terminology.
Every region analysed had a ‘net warming’ during winter. Manipur had the largest change since 1970 (2.3°C), while Delhi had the smallest (0.2°C). “Winter is the fastest warming season for 12 out of the 34 States and territories considered. This is second only to autumn, which was the fastest warming season in 13 regions,” the analysts noted.
There were significant differences in the pattern of temperature changes during the winter. The southern part of the country had “strong” warming in December and January. Sikkim (2.4°C) and Manipur (2.1°C) had the largest changes in temperature in December and January, respectively. The northern part of the country had weaker warming and even cooling during December and January. Delhi had the lowest rates during this period (-0.2°C in December, -0.8°C in January), and among the States, Ladakh (0.1°C in December) and Uttar Pradesh (-0.8°C in January) had the lowest warming rates. 2 The pattern changes dramatically between January and February. All regions have warmed in February, but the warming is especially pronounced in many of the regions that showed cooling or low warming in the previous months. Jammu and Kashmir had the highest warming (3.1°C) and Telangana had the lowest (0.4°C).
In northern India, the contrast between January trends (cooling or slight warming) and February (strong warming) implied that these regions now have the potential for abrupt transitions from cool winter-like temperatures to the much warmer conditions that traditionally occurred in March.
The largest jump in warming rates occurred in Rajasthan, where the warming in February was 2.6°C higher than January. A total of nine States and territories showed a January-February difference of more than 2°C: Rajasthan, Haryana, Delhi, Uttar Pradesh, Himachal Pradesh, Ladakh, Punjab, Jammu and Kashmir, and Uttarakhand. “This supports the reports that it feels like spring has disappeared in many parts of India,” the report noted.
Meteorologists have earlier ascribed the warming of winter in southern India and the lack of rainfall in the north in winter due to an aberration in the pattern of Western Disturbances and the jet stream, winds that originate in the Mediterranear and bring moisture to north India during winter.
