Why is the Arabian Sea so warm this spring? It is well known that the Indian Ocean sees a confluence of additional heat from the Pacific through the Indonesian Seas as well as through the direct pipeline from the Southern Ocean. The Arabian Sea is seeing additional warming contributions through the atmosphere from the Arctic and North Atlantic during the winter, and from the northwestern Pacific during the spring. The largest land warming occurring over West Asia into the Mediterranean (between 1.5 degrees and 2 degrees Celsius above long-period average) is likely adding to this. The temperature anomalies for April and the average warming from January to April clearly show that the Arabian Sea is much warmer than normal this year. Surface temperature anomalies for April 2023 as departures from a long-period average highlight the cooling over India (between 0.5 and 1 degree Celsius) and the warming over Western Asia into the Mediterranean as well as the Arabian sea (between 1 and 1.5 degree Celsius).

The significance of the Arabian Sea warming becomes clearer when we consider the percentiles of the temperature anomalies. Temperature percentiles for April 2023 show that the entire Arabian Sea and the tropical Indian Ocean were much warmer than the long-period average.

From January to April this year, average temperature percentiles underscore the unique local and remote forces that kept the Arabian Sea well above normal temperatures. We now need to watch Biparjoy for the so-called rapid intensification, where winds within a cyclone can accelerate by more than 55 km/h within just 24 hours. Two of these episodes have happened already.

Lest we presume that the Arabian Sea is warming purely due to global warming, we should not forget that natural variability is a key player in locally adding to or subtracting from global warming impacts. The key factor here is the transition from the La Niña winter of 2022-23 to the upcoming El Niño summer of 2023-24. The monsoon tends to experience its largest deficit of around 15% during such a transition from a La Niña winter to an El Niño summer. But alas, even a drier monsoon will not spare northwestern India and Pakistan from extreme rain. The soaking from Biparjoy and the wet soils may leave the region much more vulnerable to additional monsoon extremes to follow. It is very critical, therefore, to be prepared for extreme events in the coming months.

The good news in this wild swing of the climate hammer is that India’s investments in weather and climate forecasting have led to greatly improved cyclone forecasts as well as forecasts at short (days 1-3), medium (days 3-10), and extended (weeks 2-4) range, comprising the so-called ready-set-go forecast system. A seasonal or an extended range forecast can help disaster management agencies to “ready” the system with allocations of resources and personnel. Medium-range forecasts allow the “set” step to go into action by moving the equipment into place, readying shelters, food, water, and warning people, while also preparing the health care system. Short-term forecasts set in motion the “go” step to save lives and property. So even as India utilises its expertise in natural disaster management, future forecasts would do well to keep an eye on the unusually warming Arabian Sea, and the unpredictable consequences when the climate crisis combines with local factors.

Raghu Murtugudde is visiting professor, IIT-Bombay and emeritus professor, University of Maryland The views expressed are personal