The increasing intensity of summer heat in Odisha is no longer merely a seasonal discomfort. It has emerged as one of the most visible manifestations of climate variability and global warming. A recent scientific study conducted by Bishnupada Sethi along with Sarat Chandra Sahu, and other researchers provides important insight into how El Nino has influenced rising temperatures and heatwave activity across coastal Odisha over the last five decades. The study analyses long-term surface air temperature variability and heatwave incidences between 1969 and 2022 using data from seven meteorological stations located across coastal Odisha.
The research covers Bhubaneswar, Balasore, Chandbali, Cuttack, Paradeep, Gopalpur and Puri stations representing both inland-coastal transition zones and maritime coastal environments. By examining monthly and seasonal temperature behaviour, heatwave frequency and long-term climatic trends, the researchers reveal a strong relationship between El Nino years and extreme summer conditions in Odisha.
El Nino is a periodic warming of sea surface temperatures over the central and eastern Pacific Ocean. Though geographically distant from India, it significantly alters global atmospheric circulation patterns. In India, El Nino is generally associated with weakened monsoon rainfall, prolonged dry spells and enhanced summer temperatures. The Odisha study demonstrates that these global climatic disturbances have direct regional consequences, especially in intensifying heatwaves across the coastal belt.
According to the research findings, the strongest warming episodes in coastal Odisha coincided with major El Nino years such as 1987, 1998, 2010 and 2016. The study employed a temperature departure index (TDI), which measures deviations from long-term average temperatures, along with five-year moving averages to identify long-term warming variability. The results clearly show that periods of high temperature variability aligned with major El Niño events.
The analysis of March temperatures revealed prominent warming peaks during the early 1980s and early 2010s in stations such as Bhubaneswar, Chandbali and Gopalpur. These warming peaks corresponded to the El Niño years of 1987 and 2010. It was observed that March 1990 recorded one of the highest temperature index values in Bhubaneswar, while 2010 witnessed increased heatwave activity across coastal Odisha.
The study further notes that April experienced even stronger climatic anomalies. During the powerful 1997-98 El Nino phase, several stations including Chandbali, Bhubaneswar and Paradeep recorded exceptionally high temperature departure indices. A similar pattern emerged during the 2015-16 El Nino event, when Odisha experienced one of the highest frequencies of heatwave days in the entire 54 year study period.
The year 1998 remains particularly significant in Odisha’s climatic history. Following the strong 1997-98 El Nino event, Odisha witnessed a devastating heatwave disaster in which more than 2,000 people reportedly lost their lives. The research identifies this year as a clear example of how large-scale global climate variability can trigger deadly regional heat extremes.
Through detailed statistical analysis, the study identifies clear warming tendencies during the pre-monsoon season. The researchers applied the non-parametric Mann-Kendall trend test and Sen’s slope estimator to evaluate long-term climatic trends. Significant positive warming trends were observed in Paradeep and Puri during the March-May season, while Bhubaneswar and Chandbali exhibited increasing but statistically weaker warming patterns.
One of the major findings of the research is the spatial heterogeneity of heatwave behaviour along Odisha’s coast. Inland-coastal transition stations such as Bhubaneswar and Chandbali recorded stronger heatwave activity compared to maritime stations like Puri and Gopalpur. According to the findings, the moderating influence of the Bay of Bengal reduces thermal extremes in purely coastal zones, while urbanised inland areas experience greater heat retention and higher daytime temperatures.
The study also identifies periodic fluctuations in temperature variability that appear linked to large-scale climatic oscillations such as El Nino and La Nina. The researchers observed repeated oscillatory warming episodes during strong El Niño years, indicating that Odisha’s coastal climate is strongly influenced by global ocean-atmosphere interactions.
Meteorologically, the study explains that severe heatwave conditions in Odisha develop through a combination of regional and global factors. During El Nino years, cloud formation and pre-monsoon rainfall tend to weaken, leading to clearer skies and stronger solar heating. Simultaneously, hot and dry north-westerly winds from inland India dominate over Odisha. These winds often suppress the cooling effect of sea breeze from the Bay of Bengal, creating prolonged periods of extreme daytime heat.
The research also highlights the role of urbanisation in intensifying local heat conditions. Bhubaneswar and Cuttack, which have undergone rapid urban growth over recent decades, show evidence of enhanced heat retention linked to land-use changes, increasing concrete infrastructure and declining vegetation cover. These urban heat island effects amplify the impact of broader climatic warming.
An important scientific contribution of the study is its use of homogenised temperature datasets. Earlier climate studies in Odisha often relied on raw observational records that contained inconsistencies arising from station relocation, instrumentation changes and urban development around weather observatories. To overcome these limitations, the researchers used a sophisticated homogenisation techniques, allowing them to remove artificial discontinuities and improve the reliability of long-term climate trend analysis.
The study also analysed seasonal heatwave frequency during both March-May and March-June periods. Bhubaneswar and Chandbali displayed gradual increases in heatwave days since the 1980s, whereas stations such as Paradeep, Gopalpur and Puri showed relatively stable or weak trends due to stronger maritime moderation. Interestingly, Cuttack recorded a statistically significant decreasing trend in heatwave frequency during March-May.
When June was included in the analysis, most stations exhibited flattening or declining heatwave trends because the onset of the southwest monsoon interrupted prolonged heating episodes. This finding highlights the important influence of monsoon timing in regulating the duration and intensity of heatwaves in Odisha.
The study further emphasises that while pre-monsoon months host the highest temperatures, temperature variability is actually greater during winter and post-monsoon months due to regional atmospheric circulation anomalies. Nevertheless, heatwaves remain the most dangerous climatic extreme because of their direct impact on human health, agriculture and infrastructure.
The research provides strong scientific evidence that El Niño plays a major role in intensifying heatwave conditions in coastal Odisha. Their analysis demonstrates that global climatic oscillations, combined with regional atmospheric processes and urbanisation, are reshaping the thermal characteristics of Odisha’s coastal environment. The repeated coincidence of severe heatwaves with strong El Niño years indicates that future warming episodes may become more dangerous if global temperatures continue to rise.
The findings of this five-decade study are particularly important because they establish a clear regional climate signal based on long-term scientific evidence. By linking El Nino events with heatwave variability, the research contributes significantly to understanding climate extremes in eastern India and highlights the growing vulnerability of coastal Odisha to rising temperatures and recurring heat stress.
Dr. Bishnupada Sethi
The author is the Chairman of OFDC and Chief Administrator of KBK districts of Odisha.
