As climate change exacerbates heat stress around the world, the Copernicus Climate Change Service (C3S) and European Centre for Medium-Range Weather Forecasts (ECMWF) have created Thermal Trace, a fast and intuitive application to explore maps, charts and decades of data to monitor heat and cold stress globally and how this is changing over time.
Image: Thermal Trace application showing peak heat stress reached across the globe in June 2025,
from moderate to extreme based on the ERA5-HEAT Universal Thermal Climate Index.
With heat stress being already a leading cause of weather-related deaths, according to the WHO, and heatwaves becoming more frequent and more intense with climate change, understanding and monitoring thermal stress and its impacts on human health are critical.
To enhance understanding of heat and cold stress, the application provides data based on the Universal Thermal Climate Index (UTCI), which not only considers the temperature, but also accounts for humidity, wind speed, sunshine and the heat emitted by the surroundings, as well as how the human body reacts to the environment. The UTCI provides a ‘feels-like temperature’ based on the combination of these factors.
Thermal Trace allows a wide range of users, including scientist, policymakers, journalists and the general public, to access the data in an easy and intuitive manner with just a few clicks.
Users can visualise the data through maps and charts, showing how these indicators have varied and changed across the globe over the last 85 years up to five days before present day. The data behind the charts can be downloaded directly from the app, and the full dataset is available in the Climate Data Store.
The app’s launch includes the publication of the post-processed thermal comfort data contained in the app, such as the number of heat stress days or tropical nights, and maximum/minimum statistics at daily, monthly, seasonal and annual time scales. The app is completely free to use and does not require users to create an account.
Rebecca Emerton, C3S Climate Scientist, commented:
“The repeated and intense heatwaves that many of us have experienced in recent months are just one example of the impact of heat stress on people, and heatwaves are becoming more frequent and intense with climate change. With Thermal Trace we aim to empower citizens and decision makers by ensuring a wealth of data on thermal stress is more accessible than ever before.”
Read more about the app in this article.
Click here to access the app online
ECMWF is a key player in Copernicus, the Earth Observation component of the European Union’s Space programme, by implementing quality-assured information on climate change (Copernicus Climate Change Service), atmospheric composition (Copernicus Atmosphere Monitoring Service), and contributing to information on flooding and fire danger (Copernicus Emergency Management Service).
ECMWF is both a research institute and a 24/7 operational service, producing global numerical weather predictions and other data for Member and Co-operating States and the broader community. It operates a world-class supercomputer facility for weather forecasting and holds one of the largest meteorological data archives.
Together with ESA and EUMETSAT, ECMWF also delivers the EU’s Destination Earth initiative, which is developing prototype digital twins of the Earth.
enabling the general audience, journalists, policymakers, scientists and more
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