As health systems worldwide work to reduce their environmental impact, understanding the source of their emissions is a critical first step. That's where emissions measurement comes in.
At the Centre for Sustainable Medicine (CoSM), we work with UN agencies, health ministries, regional health systems, individual hospitals, and frontline staff across Asia and beyond to measure emissions and co-develop practical decarbonisation strategies.
But what goes into measuring emissions across something as complex and sprawling as a national health system?
What data do you need?
To begin a baseline project, we collaborate closely with health system data owners and stakeholders to collect and integrate three key datasets:
- Activity data captures what a system physically does. For example, electricity consumed, fuel burned, or the number of inhalers used. It offers high precision but often covers only parts of the system and can take more time and effort to gather.
- Financial data reflects what a system spends. Drawing from national health spending or hospital ledger data. It provides broad coverage, including supply chain activities that are harder to track through activity data alone.
- Emissions factors link both types of data to their environmental impact, converting usage or spending into greenhouse gas estimates.
Together, these three datasets enable full data coverage for a health system baseline and enable the construction of a 'hybrid' emissions model.
Our methodology
Once data is collected, each data point is linked to its corresponding emissions factors. To avoid double-counting, items already covered by activity data (such as energy bills) are removed, and non-emitting expenses (like wages) are excluded. Where data allows, we disaggregate emissions data across categories such as care type, sector, or expenditure type to improve usability for clinicians and policymakers alike.
Why emissions modelling matters
A clear, traceable emissions baseline helps health systems:
- Identify hotspots and emission drivers across the entire system
- Prioritise action by linking emissions with cost, health impact, and feasibility
- Set science-based targets and credible performance indicators
- Track progress and course-correct over time
When done right, emissions modelling becomes a powerful enabler, helping health systems move from good intentions to concrete action. While models inevitably carry some uncertainty and take time to build, waiting for perfect data shouldn't delay progress. With the right guardrails, early action based on the best available evidence can still lead to meaningful and measurable improvements.
As part of the WHO-led Alliance for Transformative Action on Climate and Health (ATACH), the Centre for Sustainable Medicine is working in close partnership with WHO and NHS England to develop comprehensive guidance on health system carbon baselining, tailored for ministries of health and national health systems. This landmark resource is set to launch at COP30—stay tuned for more.
Want to learn more about baselining?
Download our resource guide!
Discover what it really takes to build a solid GHG emissions baseline - and what every health system needs to know before getting started.