Global Scientific Synthesis Report on Extreme Heat and Health

Duration: 2024-2026

Partners: WMO / International experts / GHHIN Management Committee

Project Lead(s): Kristie Ebi (University of Washington)

Extreme heat is a growing global health threat, yet reliable and policy-ready data remain scarce. To address this gap, and aligned to the UN Secretary-General’s Call to Action on Extreme Heat, WMO is producing the first global scientific synthesis report focused on the health impacts of extreme heat. Coordinated by the University of Washington and developed with over 40 international experts through the Global Heat Health Information Network, this report will consolidate the best available science to answer key policy questions and support evidence-based decisions to reduce extreme heat risks worldwide. The planned publication date is November 2026.

1. Provide a comprehensive overview of the current scientific understanding of extreme heat and health.
2. Identify effective interventions and highlight knowledge gaps, success stories, and areas needing investment.
3. Equip policymakers with evidence-based messages and tools to inform heat risk reduction strategies.

1. Current magnitude and pattern of heat-related burdens: injuries, illnesses, deaths, and worker productivity, including trends over time, climate attribution, and shifts in population sensitivity. Chapter led by Dr. Jason Lee, National University of Singapore.
2. Vulnerable populations and regions: risk awareness, equity dimensions, and interactions with other environmental and socioeconomic drivers. Chapter led by Dr. Caradee Wright, South African Medical Research Council
3. Effectiveness of interventions: evidence of what works, lessons learned, economic considerations, and mainstreaming health in all policies. Chapter led by Dr. Ollie Jay, University of Sydney, Dr. Shubhayu Saha, Emory University and Dr. Peter Berry, Health Canada
4. Climate risk assessment for 2050: how climate change and development scenarios will shape the future burden of heat-related mortality and morbidity. Chapter led by Dr. Yoonhee Kim, University of Tokyo & Dr. Glenn McGregor, Durham University
5. Long-term planning for resilience: the role of urban planning, governance, and structural adjustments in reducing risks. Chapter led by Dr. Ladd Keith, University of Arizona
6. Data, methods, and tools: suggested indicators and approaches to monitor and evaluate heat-health risks and resilience. Chapter led by Dr. Sari Kovats, London School of Hygiene and Tropical Medicine
7. Summary and conclusions: priorities for action, urgent knowledge gaps, and a policy-relevant synthesis for decision-makers. Chapter led by Dr. Kris Ebi, University of Washington.

The report will address the following key policy questions:

• What is the recent magnitude and pattern of heat-related injuries, illnesses, deaths, and worker productivity?
  • Overview of the role of physiology and behaviour
  • Thermal limits
• What is the evidence that current heat-related injuries, illnesses, and deaths were caused by climate change?
• Which populations and regions are particularly vulnerable? What is the awareness of the health risks of exposure to extreme heat?
• How effective are current interventions to protect the most vulnerable?
• How can heat-related inequities be proactively and effectively reduced?
• How is the character of heatwaves expected to shift by mid-century because of climate change?
• How could heat-related illnesses and deaths evolve under climate and development scenarios?
• What data, methods, and tools are needed to monitor and evaluate changes in the burden of heat-related health outcomes and in the effectiveness of interventions?
• What is the evidence for the effectiveness of long-term adjustments in urban planning?
• What will be the economic costs and what economic resources will be needed?
• What urgent and immediate knowledge gaps need to be filled?

• A peer-reviewed, policy-relevant global synthesis report structured around risk management.
• An executive summary for decision-makers highlighting key findings and recommendations.

• A trusted global baseline for global understanding and tracking of heat-health risks.
• Stronger alignment of national and international heat-health policies with the latest evidence.
• Increased global investment in scalable, science-based solutions for heat resilience.