Key Messages

Extreme heat poses challenges across the world, but heat-related deaths are largely preventable.

Our Network’s efforts to save lives are driven by the latest science around heat and health, summarized in the following key messages from the the Working Group II contribution to the IPCC’s Sixth Assessment Report – AR6 Climate Change 2022: Impacts, Adaptation and Vulnerability – released 28 February 2022.

1. Heat is a growing health risk

Heat is a growing health risk, due to burgeoning urbanisation, an increase in high temperature extremes, and demographic changes in countries with ageing populations (very high confidence). A significant proportion of heat-related mortality in temperate regions is linked to observed anthropogenic climate change, but greater evidence is required for tropical regions. For some heatwave events over the last two decades, associated health impacts can be at least partially attributed to observed climate change. In assessed regions, some mental health challenges are associated with increasing temperatures (high confidence).

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2. Climate change is significantly increasing exposure to heat waves

Globally, population exposure to heatwaves will continue to increase with additional warming, with strong geographical differences in heat-related mortality without additional adaptation (very high confidence). Regional level assessments of changes in population heat exposure for Africa, Europe, the US, China and India corroborate the general findings at the global level – the impact of warming is amplified under divergent regional development pathways (e.g., SSP4 – inequality) compared to those fostering sustainable development (e.g., SSP1 – sustainability) (high confidence).

3. Certain groups face a disproportionately high risk to extreme heat.

Excess deaths during extreme heat events occur predominantly in older individuals and are overwhelmingly cardiovascular in origin (very high confidence). Maternal heat exposure is a risk factor for several adverse maternal, foetal, and neonatal outcomes, with additional research needed on future impacts of climate change on maternal, foetal and neonatal health.

4. Population growth in tropical and subtropical regions will soon contribute to strong geographical differences in heat-related mortality.

Strong geographical differences in heat-related mortality are projected to emerge later this century, mainly driven by population growth in regions with tropical and subtropical climates (very high confidence). Whether adaptation is considered or not, the consensus is Central and South America, Southern Europe, Southern and Southeast Asia and Africa will be the most affected by climate change related increases in heat-related mortality (high confidence).

5. The impact of heat on labour productivity and GDP is a growing concern.

The effect of climate change on productivity is projected to reduce GDP at a range of geographical scales (high confidence). Potential hours of work lost due to heat has increased significantly over the past two decades, and some regions are already experiencing heat stress conditions at or approaching the upper limits of labour productivity. For example, measuring economic costs using occupational health and safety recommendations, it was estimated that RCP8.5 would result in a 2.4% reduction in global GDP, compared to a 0.5% reduction under RCP2.6.

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6. The Urban Heat Island effect will increase heat risk in cities.

Hot extremes including heatwaves have intensified in cities (high confidence). Heat risks are expected to be greater in urban areas due to changes in regional heat exacerbated by ‘heat island’ effects (high confidence).

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7. Extreme heat compounded the impacts of the COVID-19 pandemic.

During the pandemic, extreme weather and climate events such as droughts, storms, floods, wildfires and heat waves continued, resulting in disastrous compounding impacts (high confidence). Between March and September 2020, 431.7 million people were exposed to extreme heat in areas managing active transmission of COVID-19.

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Heat and COVID-19

8. Heat action plans that incorporate early warning and response systems are important adaptation solutions.

Adaptation options for future extreme heat risks include heat action plans that incorporate early warning and response systems for urban and non-urban settings; tried, tested, and iteratively updated response strategies targeting both the general population and vulnerable groups such as older adults or outside workers; and effective stakeholder communication plans (high confidence).

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9. Long term urban planning and design can complement short-term responses to heat health risks.

Short-term responses can be complemented by longer term urban planning and design, including Nature-based Solutions that mitigate urban heat island effects (high confidence).

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10. Multi-sectoral approaches will benefit long term responses to the health risks of heat.

A multi-sectoral approach, including the engagement of a range of stakeholders, will likely benefit the response to longer term heat risks through the implementation of measures such as climate sensitive urban design and planning to mitigate urban heat island effects (high confidence).

A note on IPCC calibrated language:

Each finding is grounded in an evaluation of underlying evidence and agreement. A level of confidence is expressed using five qualifiers: very low, low, medium, high and very high, and typeset in italics, e.g., medium confidence. The following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99-100% probability, very likely 90-100%, likely 66-100%, as likely as not 33-66%, unlikely 0-33%, very unlikely 0-10%, exceptionally unlikely 0-1%. Assessed likelihood is typeset in italics, e.g., very likely. This is consistent with AR5 and the other AR6 Reports. Learn more >

Key Messages and Priorities for Specific Contexts

Workplace Heat Risk

Urban Heat Risk

COVID-19

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