As every year, Indians were eagerly awaiting monsoon rains by the end of May. Instead, they got back-to-back cyclones on the East and West coasts, locust outbreaks in the North, and scorching heat waves throughout the country.
The cyclones hit two of the most populated metropolitan cities in the world – Kolkata and Mumbai. The propensity towards similar climatic events has increased around the Indian Ocean. Unseasonal storms in East Africa and the Arabian Peninsula, which triggered the locust outbreaks in South Asia and the wildfires in Australia, are part of these unusual events. At the same time, a series of heatwaves led to the bleaching of coral reefs along the Indian coast, which has evolved as a hotspot for climate extremes, rampaging the marine ecosystem.
Cyclones
The North Indian Ocean accounts for only about 7% of the total number of tropical cyclones that occur globally. However, more than 80% of the global fatalities occur in this region, particularly around the Bay of Bengal. Hence, any rise in the frequency or intensity of cyclones in this region is of grave concern – and that is exactly what is happening.
Cyclones draw their energy from the warm ocean waters. As the Indian Ocean is rapidly warming, it is brewing more intense storms during some seasons. India has come a long way in cyclone forecasting since 1999, when the super cyclone on the East coast killed several thousands. From fatalities running into five-digit numbers, we have moved to two digits.
This is owing to improvements in forecasting systems as well as efficient communication between government departments. In the case of cyclones Amphan and Nisarga, the India Meteorological Department gave a skillfully accurate forecast of the track and intensity, which saved lives.
In recent years, we see that cyclones are forming quite quickly: Amphan intensified from a category-one to a category-five cyclone within 18 hours. Our research shows that high ocean temperatures are conducive to such rapid intensification of cyclones in the North Indian Ocean.
The buoys in the Bay of Bengal and Arabian Sea basins registered surface temperatures in the range of 30°C–33°C. These are record temperatures driven by climate change – we have never seen such high values until now. Weather forecast models find it a difficult task to simulate this rapid cyclone intensification due to ocean warming, and that is a challenge that we need to address in near-term.
African locusts and Australian wildfire
The locust outbreak started after warm waters in the Western Indian Ocean in late 2019 fuelled storms and substantial amounts of rains over East Africa and the Arabian Peninsula. These warm waters were caused by a phenomenon called the Indian Ocean Dipole – with warmer than usual waters to its West and cooler waters to its East. Rising temperatures due to global warming amplified the dipole and made the Western Indian Ocean particularly warm.
Heavy rain triggers the growth of vegetation in arid areas where desert locusts can then grow and breed. These locusts then followed the winds and rains to the Indo-Pak region early this year. They found greener pastures over North India as the pre-monsoon rains during March–May were in excess.
While the warm waters in the West Indian Ocean enhanced the storms over there, it also pushed dry air over the Eastern Indian Ocean. This accentuated the dry summer over Australia, triggering some of the worst bushfires that the country has seen.
Marine heatwaves
A less-discussed element of ongoing climate change is the marine heat waves. These are the ocean’s erratic response to increased warm waters, and are quite similar to the ones over land. Coral reefs occupy only 0.1% of the planet’s surface but are home to 25% of all the marine life found in the ocean.
An underwater survey showed that 85% of the corals in Gulf of Mannar near the Tamil Nadu coast got bleached in May after the ocean temperatures peaked. Satellite observations reveal that number of marine heatwaves has likely doubled in recent decades and have also become longer-lasting, more intense, and extensive. Fisheries catch in the Indian Ocean appears to have already been impacted by the effects of warming on growth, reproduction and survival of fish stocks.
The way forward
With an event like the tropical cyclone, it is not just the intensity of the winds that increased, but also the amount of rainfall, as warmer air holds more moisture; the inundation due to storm surges, as sea levels have risen; and saline water intrusion.
When these events cascade and overlap – called compound events – the threat gets much more severe. Considering that cities like Kolkata and Mumbai have a bellying population where land development comes at the cost of mangroves, rivers and floodplains, such events present challenging scenarios.
India already has a National Climate Change Action Plan and related policies. However, these policies haven’t been adequately followed up. An IIT-Bombay study reveals that floods in Indian cities are more of a management problem. India can – and should – take up the climate crisis as an opportunity to lead other countries in the research and development of renewable energy resources and energy-efficient infrastructure.
Our weather forecast system is sound, but we need early warning systems that integrate the multiple weather events with the human demographics and land use at the local level. The Indian Ocean rim hosts one-third of the world population and as extremes rise, we need early warning systems in all these regions, including East Africa and South Asia. Efficient forecasts require efficient monitoring of the ocean – but we have gaps there too.
Now, the Covid-19 pandemic, which is severely limiting our ability to maintain the Indian Ocean Observing System array, has presented a new dilemma. One of the buoys which recorded peak ocean temperatures in the Bay of Bengal stopped working after the cyclone. We need to join all these missing dots such that we can monitor and address the compounding crisis.
With the monsoon forecasted to be normal this year, the winds may bring in a good amount of fertile rains from the Indian Ocean during the season. Human memory is short and we often get complacent as events pass by. The impact of Indian Ocean is far beyond what we have imagined – as it can churn out intense cyclones, heavy rains and even locusts. We need to consistently and continuously work towards adapting and mitigating climate change in the Indian Ocean – for we have seen her furious face many a times.
Update: The photo on this article was updated on June 27, 2020.
