Compound climate events are on the rise. It’s time for action
Compound events - where two or more hazards, such as heatwaves and floods, occur simultaneously or in close succession - are . This phenomenon often results in more severe negative outcomes than if each hazard were to occur separately. Recent incidents in Pakistan and the United States highlight existing resilience gaps, and the adaptation solutions required to reduce the impact of compound events.
Multiple stressors put resilience to the test
As climate change intensifies the frequency and severity of extreme weather events, the phenomenon of compound events has become increasingly critical to understand and address.
Compound events, can interact in a way that creates more severe outcomes than if they occurred both individually, as multiple stressors can exceed the coping capacity of a system more quickly than individual stressors occurring in isolation. exacerbates these risks through the , impervious surfaces, and inadequate drainage systems, increasing exposure and vulnerability.
Simplified visual of compound heat and flood events. These events affect all five capitals: natural (e.g., environmental degradation), social (e.g., displacement), human (e.g., health impacts), financial (e.g., economic losses), and physical (e.g., infrastructure damage and/or loss of critical services), underscoring the need for holistic resilience strategies. Source: Red Cross Red Crescent Climate Centre
In 2022, Pakistan faced a that was soon followed by unprecedented monsoon rains. The extreme heat had dried out the soil, reducing its ability to absorb water and exacerbating flooding that displaced over 33 million people and inundated a third of the country. Urban areas like Karachi struggled with housing shortages and disease outbreaks as displaced populations sought refuge. The economic impact was staggering, exceeding $30 billion, pushing millions into poverty.
In July 2024, struck Texas resulting in extensive flooding and widespread power outages. As recovery efforts commenced, a severe heatwave followed, with temperatures soaring above 100°F (37.7°C). The lack of electricity meant that , locations with active cooling measures such as air conditioning where people could go to seek relief from heat, were unavailable, leaving residents vulnerable to dangerous heat-related conditions. Hospitals quickly became overwhelmed with patients suffering from heat stress and carbon monoxide poisoning due to unsafe generator use.
Both of these examples highlight the urgent need for resilient infrastructure, including drainage and power systems, capable of withstanding compound events. More must also be done to assess the risk of multi-hazard events, and to respond accordingly.
Adaptation solutions for compound events
By combining multi-hazard approaches, nature-based approaches, smart urban design, and community-led initiatives, cities can create safer, more sustainable environments. Investments in these solutions not only tackle immediate climate hazards but also against the growing threat of compound events.
- Multi-hazard approaches to risk assessment, planning and preparedness - for example, through backup power systems, multi-purpose cooling and evacuation centers - ensure adaptation strategies are built to address the interconnected nature of climate risks.
- offer a powerful approach to managing the impacts of both heatwaves and floods, while delivering broader ecological benefits. Urban green spaces - such as parks, green roofs, and urban forests - play a crucial role in cooling cities through shade and evapotranspiration, while also improving water absorption to mitigate flood risks.
- Climate-smart urban planning is essential for addressing compounding climate events. Strategies that incorporate smart design, such as , elevated structures, building designs and materials that improve ventilation and rooftop rainwater harvesting systems can significantly enhance resilience.
- Community-Based Adaptation leads to more effective resilience outcomes. Communities are at the forefront of adapting to compound events and empowering residents through education and engagement is vital to ensure adaptation efforts are tailored to local needs.
Learn more about compound events
To support practitioners in understanding compound events and learn about adaptation solutions to address compound flood and heatwave, Alliance partners including the Institute for Social and Environmental Transition-International, International Federation of Red Cross and Red Crescent Societies, London School of Economics and Political Sciences, Mercy Corps and the Z Zurich Foundation have worked together with the to publish Double Jeopardy: Addressing compound flood and heatwave events.
By providing evidence-based insights, case studies from Pakistan and the United States and practical recommendations, this paper provides practitioners with actionable adaptation solutions that address both heat and floods, with further co-benefits for improving overall quality of life, environmental sustainability, and economic stability.