The India Meteorological Department recently announced that temperatures across the country are expected to rise above normal levels from March to May, indicating a harsh summer. More alarming is the Copernicus climate bulletin that confirms that February 2024 was the warmest ever recorded globally. It was 1.77°C warmer than February’s average for 1850-1900, the designated pre-industrial reference period.
The global average temperature for the past 12 months (March 2023 to February 2024) is the highest on record — 0.68°C above the 1991-2020 average and 1.56°C more than the 1850-1900 pre-industrial average. The January global surface temperature was 1.27°C above normal, making it the warmest January on record. This was 0.04°C above the previous record from January 2016.
While summer has just started in other parts of the country, the Western coast has been experiencing extraordinarily hot conditions from January onwards. According to Dr S Prasanna Kumar, emeritus scientist at the National Institute of Oceanography (NIO), the current situation is driven by three factors that are acting in tandem. They are (1) the rapid warming of the Arabian Sea which is largely anthropogenic; (2) the inter-annual variation in the warming due to El Nino when the Arabian Sea becomes hotter than normal; and (3) the peaking of the solar cycle, which means the global temperature will be at the highest due to incoming solar radiation.
Besides, the Arabian Sea has been warming at a much higher rate, which will have an impact over the monsoon pattern. The surface temperature of the Arabian Sea has risen by 1.7°C, way higher than elsewhere. While El Niño conditions are expected to dissipate by April, the rapid warming of the Indian Ocean has set alarm bells ringing for India. The sea surface temperature of the Indian Ocean has increased by 1.1°C as compared to other oceans where the rise is only 0.7°C. This could have a devastating effect on agriculture in the Indian subcontinent and adversely affect marine ecosystems. It could change the monsoon circulation and rainfall patterns as well.
El Niño in the mid-2023 influenced temperatures during the rest of the year. El Niño is characterised by the emergence of a large area of relatively warm water in the eastern equatorial Pacific. The warming of the Indian Ocean and El Niño have created a multiplication effect on the Indian summer.
Besides, the Indo-Pacific warm pool significantly impacts the atmospheric process of the Indian Ocean. The warm pool is a large area located at the Western Pacific Ocean and the eastern side of the Indian Ocean, including Java and Sumatra. It has a permanent surface temperature above 28°C and is therefore called the ‘heat engine’ of the globe. As the warm pool straddles the equator and the adjacent areas, its surface waters stay over 28°C round the year. The warm pool maintains such temperatures down to approximately 200 metres in most regions.
“During El Nino, warm water from the warm pool flows to the Eastern Pacific Ocean. This has an impact over the Walker Circulation in the atmosphere. Walker Circulation is an east-west circulation of the atmosphere above the tropical Pacific, in which air rises above warmer ocean regions in the west and descends over the cooler ocean areas in the east. At normal times, two branches of air rise from the warm pool. While one branch sinks in the eastern side of the Pacific, the other branch flows over the Indian subcontinent and sinks in the Arabian Sea west of Somalia. This controls the climate in the Indian subcontinent,” said Prasanna Kumar. During El Niño, surface waters in the central and eastern Pacific Ocean are more warm than usual. This warm water flows to the East Pacific and the Walker Circulation moves to the Central Pacific Ocean. During this time, the Eastern Indian Ocean and the Western Pacific is cold. As the air mass sinks in this area, the Arabian Sea and the Somalia region experience hot weather conditions. But once it cools down, there can be intense rainfall in certain regions of the Indian subcontinent.