A new global health assessment is urging governments to treat climate change as an urgent public-health challenge, placing extreme heat, drought and other risks alongside the familiar debate over emissions targets. The 2026 Lancet Countdown report, produced by an international research collaboration led by University College London with strategic collaboration from the World Health Organization, tracks 54 indicators linking climate change and health.
The WHO summary of the report says that in 2023 heat was associated with an estimated 710,000 deaths worldwide, a record in the report’s series, and that more than 70% of that burden was attributable to human-caused climate change. The report also estimates that annual average heat-related deaths rose by nearly 36% in the years following the Paris Agreement compared with the previous decade. These are modeled estimates, not a list of death certificates that individually identify climate change as the cause.
What the heat estimate measures
That distinction matters. Researchers estimate the contribution of climate change by comparing observed conditions with a counterfactual climate absent human influence, using methods that vary by indicator. “Associated with” describes a health burden linked to heat exposure; “attributable to climate change” is a modeled estimate of the portion associated with human-caused warming. Neither phrase means that every individual death can be assigned to a single cause. The figures are designed to show population-level risk and trends.
How extreme heat harms health
Heat affects health through several pathways. It can strain the body’s ability to regulate temperature, worsen existing cardiovascular or respiratory conditions and make outdoor work more dangerous. High temperatures can also disrupt sleep and increase pressure on hospitals, electricity networks and water systems. Risk is not uniform: older adults, people with chronic illness, outdoor workers, people in poorly cooled housing and communities with limited access to health services may face greater exposure or fewer options to adapt.
The report also tracks drought, hydrological extremes and economic losses associated with heat exposure. These pressures can interact. Dry conditions may affect crop yields and water availability; heat can increase electricity demand just as power systems face stress; and damaged infrastructure can interrupt medical care. The exact effects depend on local climate, land use, public-health capacity and the measures taken before an extreme event. A global average can set context but cannot replace local assessments.
Health benefits from climate action
There is a counterpoint in the report: climate action can produce health gains now. WHO says global investment in clean energy reached a record $2.1 trillion in 2025. The report notes that reductions in fossil-fuel air pollution are estimated to protect thousands of people from premature deaths each year, alongside progress in climate-resilient health systems, national adaptation plans and early-warning systems. These benefits do not cancel climate risks, but they show that policy can change exposure and outcomes.
From emergency framing to policy
The Countdown’s call to recognize climate change as a global health emergency is a policy recommendation, not a declaration by the WHO that a formal emergency status has already been enacted. Its significance is that it asks governments to judge climate measures partly by health protection: cleaner air, heat preparedness, resilient clinics and early warnings. Such a frame can connect climate decisions to services people use directly, while still requiring careful evidence about what works and who benefits.
COP31 is scheduled for November in Antalya, Turkey, and the Countdown report arrives as countries prepare to discuss climate commitments. Health language can make risks more visible in negotiations, but declarations alone do little without budgets and implementation. National plans need to identify heat thresholds, alert systems, cooling centres, worker protections and health-service continuity. They also need resources to reach low-income communities, where exposure can be high and private cooling least accessible.
A credible response should pair emergency planning with long-term emissions cuts. Adaptation can reduce harm from heat already locked in, but it cannot prevent every future increase in risk if warming continues. Clean power, efficiency, urban shade, building standards and reliable public transport can all affect exposure and pollution, though each measure has costs and trade-offs. Monitoring can show whether interventions reach vulnerable groups and reduce illness, lost work and deaths.
For readers, the strongest next step is to look beyond the headline estimate. The report’s indicators, data explorer and country resources can show which risks are worsening and where health systems are preparing. Governments should publish heat-related health data, explain the methods used, and evaluate early-warning programmes after events. Local reporting can test whether plans reach people in informal settlements, rural areas and outdoor occupations.
How to read the evidence
The report’s message is urgent but not fatalistic: climate-related health harms are growing, while some policies are already reducing pollution and strengthening preparedness. Whether the emergency framing changes outcomes will depend on whether health authorities, energy planners and local governments coordinate action, direct funding to exposed populations and report measurable results. [Interview needed: a public-health official and heat-exposed worker on how local warnings and protections function in practice.]
Turning global indicators into local protection
Global estimates can help governments see the scale of a hazard, but protecting people requires decisions at street and workplace level. Cities can map neighborhoods with limited tree cover, older housing and high outdoor temperatures, then target shade, cooling access and public alerts. Health departments can prepare guidance for clinics and emergency services before heat peaks. Employers can review rest breaks, water access and shift timing for outdoor workers. These steps should be designed with affected communities and evaluated for coverage, because a warning that cannot be received or acted on offers little protection.
Measurement also needs care. Heat-related mortality estimates rely on statistical methods and historical data, and reporting quality differs across countries. Better local death records, hospital data and occupational-health monitoring can improve understanding of who faces the greatest risks. Researchers should communicate uncertainty ranges and explain the baseline used for attribution. The Lancet Countdown’s global indicators make a case for action, while national and city data can identify which interventions are most useful in a particular place. Climate finance aimed at health should disclose the projects funded, the population reached and the outcomes measured, so that resilience is more than a line in a policy document.