Plan adaptation and mitigation to factor in growing risk of compound extremes, study suggests

• India faces a growing risk of compound extremes with some central and northern Indian states likely to be most exposed to these correlated extreme events, such as simultaneous heatwave and heavy rains or droughts swiftly followed by extreme rain, a study predicts.
• A rethink is needed on traditional ways of categorising extremes and assessing their risk for such compound events emerging from complex processes.
• Identification, mapping and avoiding high-risk zones where compound extreme events are likely to hit the hardest are among the slew of measures suggested by experts. Adaptation and mitigation measures must factor in cascading and compounding risks, they said.

India faces a growing risk of one-two punches of extreme events (or compound extremes), such as chances of high heat and heavy rain occurring together or within a week, a study suggests.

Climate change is modifying multiple types of climate-related events or hazards, in terms of occurrence, intensity and periodicity, states the IPCC’s Special Report on the Ocean and Cryosphere in a Changing Climate. It increases the likelihood of compound hazards, that comprise simultaneously or sequentially occurring events, to cause extreme impacts in natural and human systems. Compound events, in turn, trigger cascading impacts. Advancing the latest knowledge on compound extremes, the most recent IPCC report also emphasises that concurrent and repeated climate hazards occur in all regions, increasing impacts and risks to health, ecosystems, infrastructure, livelihoods and food.

According to the study published in the journal Science of The Total Environment,compound extreme events across India are likely to increase significantly in the next 80 years (2020 to 2100) as compared to 1966-2005. States of Uttar Pradesh, Bihar, Jharkhand, and Odisha are likely to be most exposed to the troubling trend of these correlated extreme events, it adds.

“The increase in exposure in these states in central northeast India (CNI) is mainly contributed by the increase in the frequency of compound extremes and increase in the population projections. Highly populated regions such as Uttar Pradesh and Bihar are located in CNI and the population in CNI is projected to increase rapidly. The rapid growth in the population will push up the odds of increased exposure of these states to compound extremes,” said the study’s corresponding author Jew Das at the National Institute of Technology Warangal, India.

“Similarly, the lower growth rate of population in the Himalayan region is the reason behind low exposure to compound extremes in the Himalayas,” said Das.

Using next-gen climate modeling, scientists predicted the likelihood of exposure of India’s populations to five combinations of compound extremes, such as simultaneous heatwaves and drought, heatwaves and heavy rain occurring together, droughts swiftly followed by extreme rain, sequential heatwaves and droughts and heatwaves followed swiftly by heavy rain, under different Shared Socioeconomic Pathways (SSPs). SSPs capture broad socioeconomic trends, such as population and economic growth, that could shape future society and depend on how quickly humans check greenhouse gas emissions.

“Many previous studies show that co-occurrence of hazards droughts, extreme rainfall events and heat waves often leads to amplified impact compared to that of individual hazards. Due to the high density and rapid growth of population in India, these climate hazards cause high mortality and affect the socio-economic wellbeing of the large population. Moreover, the changes in the occurrences of compound extremes in the observed and projected climate of India are not well quantified,” said Das, explaining the motivation behind the analysis on population vulnerability to different types of projected compound extremes under varying climate and population scenarios.

They find that of all compound extremes, the deadly duo of heatwaves and droughts occurring together is likely to affect three to five times more people across India by 2100 compared to earlier (1966 to 2005) in the SSP 3 scenario when emissions are high, population growth is high in developing countries, countries become more competitive with each other, economic development is slow and inequalities persist or worsen amid strong environmental degradation in some regions.

They recommend a range of actions such as identification and mapping and avoiding high-risk zones where compound extreme events are likely to hit the hardest, revising and redesigning hazard-resistant structures and houses factoring in the impact of compound extremes, protecting and developing hazard buffers such as forests, reefs etc. and improving the early warning and response systems.

“We need to develop a culture of resilience and also come up with an Integrated Emergency Surveillance System to facilitate a systematic and sustained response to emergencies,” explained co-author V. Manikanta.

A 2021 analysis by the Ministry of Earth Sciences had spotlighted that floods and cyclones contribute to maximum human deaths in India from extreme weather events (EWEs) but deaths due to heatwave and lightning need urgent attention. But two or more extreme events succeeding one another or impacting regions at the same time are getting increasingly common, says Manabendra Saharia who works on developing solutions for monitoring and mitigating natural hazards. 

He noted that fresh approaches to risk assessment are needed to develop adequate climate change adaptation policies. “But traditional ways of categorising extremes and assessing their risk are inadequate for such compound events emerging from complex processes,” Saharia, principal investigator at IIT-Delhi’s HydroSense Lab, told Mongabay-India. He was not associated with the study.

Anjal Prakash, a lead author of the most recent IPCC report that focuses on impacts, adaptation and vulnerability notes that the report warns of the compounding and cascading risks related to climate change likely to unfold if adaptation and mitigation measures are not planned soon.

“The window of engagement is slowly closing and the next one and half decades are crucial for humanity. To translate the IPCC knowledge into action and to protect people, especially the most vulnerable and marginalised women, men and children, I would suggest that we get into district and sub-district level planning which is climate-resilient. All our development plans adhere to climate risks including cascading and compounding risks and therefore adaptation and mitigation measures must be planned based on this projection,” Prakash, Research Director and Adjunct Associate Professor at Bharti Institute of Public Policy, Indian School of Business, told Mongabay-India. Prakash was not associated with the study.

“Climate change is a global phenomenon, but it has localised impacts and so our scientific community must work with the policymakers and make the district level planning climate-resilient. IPCC report talks about the main ingredients of this pathway such as protecting green and blue infrastructure, reevaluating developmental plans and social protection measures for the most vulnerable women and men,” he added.