World cultural heritage, recognized as the pinnacle of humanity's achievements, is facing unprecedented threats due to climate change. Recent research has revealed that 80 % locations UNESCO is already experiencing the harmful effects associated with with heat and humidity. Critically, almost 19% of these sites are threatened with more than one key material, such as stone and wood. This requires immediate and targeted adaptation strategies.

Understanding the threat: Climate-induced stress (CIS) Study uses the Hazard-Vulnerability-Exposure (HVE) framework to assess changes in climate-induced stress (CIS) at UNESCO cultural heritage sites. Hazards are represented by compound climatic events (CEs) – sudden fluctuations in temperature and humidity that exceed the threshold values of materials. Vulnerability refers to the susceptibility of materials such as wood and stone to these extremes. For example, wood tends to crack during rapid temperature cycles around 15°C, while stone erodes during cycles around 10°C. Exposure is quantified through 3D floor plans of buildings, which determine how much of the surface is directly exposed to weathering.

Current and future threats: Hot spots and regional differences From the period 1961–1991 to 2010–2040, the CIS increased to 80 % locations, while 19 % faces a threat to both materials (stone and wood). Among the main regional hotspots include:

• Central and Eastern Europe: Records accelerating heat waves and heavy rainfall affecting up to 44 locations. Continental regions are more affected than coastal ones.
• Arab States and South America: Wood is not yet seriously threatened, but even the low-emissions scenario brings only a slight improvement, indicating the need to strengthen adaptive capacity.
• Africa: Fewer than 30 % sites here show a mitigation benefit, highlighting the urgent need for robust adaptation strategies in historically underfunded areas.
• North America: Shows the greatest potential for conservation under a low-carbon trajectory, where approximately 72 % of stone and 44 % of timber buildings could see meaningful CIS reductions.

Emission mitigation potential The study compares two scenarios of future emissions: SSP1-2.6 (low emissions, warming of ~1.8°C by 2100) and SSP2-4.5 (medium emissions, warming of ~2.7°C). The analysis shows that up to 40 UNESCO % sites can achieve significant CIS mitigation in the SSP1-2.6 scenario. While the low-emissions scenario delivers significant overall benefits for heritage, significant challenges remain. With the exception of North America, the number of sites potentially saved lags behind those already at risk.

Material differences and adaptation needs CIS on cultural heritage is not uniform and varies significantly by location, period and materials. Wooden structures are more vulnerable to repeated stress and require continuous maintenance. Conversely, stone sites can benefit from regular structural strengthening. The study highlights that no single mitigation path can protect all sites equally. It is essential that risk assessments include specific thresholds for individual materials, ensuring tailored interventions. The findings have important implications for climate justice. Exposure and relief are uneven: low-income regions, which often suffer disproportionate losses, often lack the technical and financial means to protect their heritage. Therefore, redirecting multilateral climate change financing towards heritage key to achieving the Sustainable Development Goals (SDGs) on climate justice and equity. The authors propose a multi-tiered support framework, including earmarking funds from the UNFCCC Loss and Damage Fund, including cultural assets under the Green Climate Fund, and creating “flying-lab” consortia to disseminate expertise.

Restrictions The study has several limitations: it does not include on-site adaptations, uses building floor plans as a proxy for heritage value (ignoring intangible aspects), and limits climate stressors to only daily temperature and humidity, excluding other hazards such as storm surges or forest fires. JRi

The study was published in the journal Nature.