Last year, 2020, was the eighth warmest year on record since nation-wide records commenced in 1901. Last year, the annual mean land surface air temperature averaged over the country was +0.29 degree C above normal (based on data between 1981-2010) according to the India Meteorological Department’s Statement on Climate of India in 2020. This, despite the cooling effect of La Nina, a global weather phenomenon.
The highest warming was observed over India in 2016 when the mean land surface temperature was +0.71 degree C above normal. The temperature during the pre-monsoon season was below normal by -0.03 degree C. But both monsoon and post-monsoon seasons were +0.43 degree C and +0.53 degree C respectively which contributed to the warming. The mean temperature during winter was above normal +0.14 degree C.
India’s warming was however significantly lower than the global average. The global mean surface temperature anomaly during 2020 (January to October as per the World Meteorological Organisation’s state of the global climate) is +1.2 degree C.
The annual rainfall over the country as a whole was 109 per cent of its Long Period Average (LPA) calculated for the period of 1961-2010.
The statement said 12 out of 15 warmest years were during the recent fifteen years (2006-2020). The past decade (2011-2020) was also the warmest decade on record.
Averaged annual mean temperature during 1901-2020 showed an increasing trend of 0.62 degrees C in 100 years with an increasing trend in maximum temperature (0.99 degrees C in 100 years) and relatively lower increasing trend (0.24 degrees C in 100 years) with respect to minimum temperature.
Last year, the mean monthly temperatures were warmer than the normal during all the months except March and June, the statement said. The mean temperatures exceeded the normal during September (by 0.72 degrees C, warmest since 1901), August (by 0.58 degrees C, second warmest), October (by 0.94 degrees C, third warmest), July (by 0.56 degrees C, fifth warmest), and December (by 0.39 degrees C, seventh warmest).
“2020 was one of the warmest years despite La Niña with cool waters in the east Pacific. La Niñas typically has a cooling effect on global temperatures, but this is now offset by global warming due to greenhouse gas emissions. As a result, La Niña years now are warmer than years with El Niño events of the past. As for India, data shows that the increasing trend in temperatures is the largest during the post-monsoon season and this is reflected in the 2020 post-monsoon temperatures over India, despite a full-fledged La Nina,” said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology (IITM), Pune.
“The fact that there was a rise of over 1 degrees C in global mean surface temperature over pre-industrial levels in a La Nina year is a sign of global warming. In El Nino years, the sea surface temperatures are higher so are land surface temperatures. But in La Nina years there is cooling particularly over the Indian region. Despite that, the average temperatures were higher than normal which is due to climate change. The northern hemisphere also recorded substantially above normal temperatures,” said DS Pai, senior scientist at IMD Pune.
The statement also said India experienced some extreme climate events like extremely heavy rainfall, floods, landslides, thunderstorm, lightning, cold waves which killed hundreds of people.
Bihar and Uttar Pradesh were the most adversely affected states during the year wherein more than 350 people died from each state due to thunderstorm, lightning and cold wave.
Heavy rainfall and floods claimed over 600 lives in different parts of the country during pre-monsoon, monsoon and post-monsoon seasons. Of these, 129 people were killed in Assam, 72 in Kerala (65 persons died in a single day in Munnar, Idukki district of Kerala on August 7 due to a landslide), 61 in Telangana (while 59 lives were reportedly claimed only during the period 1st to 20th October), 54 in Bihar, 50 in Maharashtra, 48 Uttar Pradesh and 38 in from Himachal Pradesh.
Thunderstorms and lightning also claimed over 815 lives from different parts of the country – 280 in Bihar, 220 in Uttar Pradesh, rest in Jharkhand, Madhya Pradesh, Maharashtra and Andhra Pradesh. Cold wave conditions also killed 150 people mainly in central India in January.
Last year, 5 cyclones formed over the North Indian Ocean. These were super cyclonic storm Amphan, very severe cyclonic storms Nivar and Gati (both over the Arabian Sea), severe cyclonic storm Nisarga and cyclonic storm Burevi.
Super cyclonic storm Amphan formed in the pre-monsoon season and crossed the West Bengal coast over Sundarbans on May 20. It claimed 90 lives and about 4,000 livestock mainly in West Bengal.
According to the WMO, Amphan is estimated to be the costliest tropical cyclone on record in the North Indian Ocean with economic losses to the tune of approximately US $14 billion.
El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean according to the National Oceanic and Atmospheric Administration (NOAA).
ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. El Niño has a warming influence on global temperatures, whilst La Niña has the opposite effect. In India for example, El Nino is associated with drought or weak monsoon while La Nina is associated with strong monsoon, above-average rains and colder winters.
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