Combining data from multiple sources enables us to extrapolate the environmental conditions faced over time by the Brown Gallery portraits. This includes sensed data and proxy data, and data on environmental conditions internal and external to Knole House.
Using Internal Sensor Data
Sensors placed in the Brown Gallery and at other locations within Knole House provide direct measurement of the internal environmental conditions faced by the paintings. In particular, sensor data for temperature and relative humidity were collected in the Brown Gallery by the National Trust throughout the period from 2000 until 2015, and separately by the Courtauld Institute of Art from 2015 until 2016.
Using External Climate Data
Internal sensor data for Knole House spans only a limited and recent time period. External climate data, which is available for a longer period of time, offers another means of tracking the environmental conditions faced by the Brown Gallery portraits. Since no modern controlled heating has been used within Knole House, we look to extrapolate environmental conditions within the Brown Gallery by correlation to the climate conditions experienced at Knole. Multiple sources are available to us for external climate data. In addition to Met Office data for the region, the National Trust has also collected exterior climate measurements around Knole House.
Using Proxy Data
Met Office data and written records offer a basis for extrapolating the environmental conditions faced by the Brown Gallery portrait set back to 1853. Conditions during the 250 years prior to this are more difficult to extrapolate. Our approach is to interpret regional conditions in Kent based on proxy data – preserved physical characteristics of the environment that can stand in for direct measurements. In particular, we look to natural recorders of climate variability such as tree rings, ice cores, fossil pollen, ocean sediments and corals. Using such proxy data is not without assumptions, such as an assumption that fireplaces in the Brown and Cartoon Gallery did not have a significant effect on the temperature.