The goal of this Theme in the National Centre for Earth Observation is to develop the theory of data assimilation, particularly methods to treat uncertainty in the data and models, so that their work underpins other applications within NCEO and partner agencies.

Its priorities are to:
- Create data-assimilation techniques for use in coupled, multi-scale Earth-system models
- Construct techniques to represent uncertainty in observations and models
- Determine surface movements of trace gases
- Quantify the impact of observations
- Develop observing-system simulation experiments