A critical review of the CSIRO Weather and Climate Data (Part 1 of 3)
Since August 2021, the CSIRO has distributed three important weather and climate datasets for use by building energy modellers:
• Typical Meteorological Year (TMY) – a collation of selected meteorological measurements, listing data at 8,760 hourly intervals to describe a ‘typical’ year of weather for a specific location. This data is published in the EnergyPlus (.epw) format and is available at https://acds.csiro.au/future-climate-typical-meteorological-year.
• Reference Meteorological Years (RMY) – conceptually representing the same information as TMY but presented in an amended version of the fixed record format of the Australian Climate Data Bank (ACDB). This data is the basis for climate information in the Nationwide House Energy Rating Scheme (NatHERS) software tools and is distributed with the CSIRO’s AccuRate software and its competitors.
• Predictive weather files – CSIRO’s predictive weather files are based on a typical meteorological year of historical weather data drawn from 1990 to 2015 and can be used to investigate the impact of climate change on building energy consumption. These are available in .epw and NatHERS-compatible formats at https://acds.csiro.au/future-climate-predictive-weather.
As the basis for NatHERS, the CSIRO’s RMY dataset is arguably the most commonly-applied pathway to demonstrate compliance with the residential energy efficiency requirements of the National Construction Code (NCC). With its transcription to the .epw format, closely related data is commonly used for simulations of commercial buildings that are used to demonstrate compliance with section JV3 of the NCC, as well as simulations for other purposes.
Exemplary Energy’s review of the CSIRO weather and climate datasets is timely as the 2022 version of the NCC is currently being finalised. Its publication is scheduled in early 2022 and the Code will come into effect mid that year.
Our detailed review of the CSIRO climate and weather data sets has revealed three major shortcomings:
1. Reliance on weather data ending in 2015 for the characterisation of a warming climate;
2. A 30-minute error in solar data in the .epw format; and
3. A lack of coincident precipitation data despite the .epw format expressly inviting it.
The first issue is well-known: The CSIRO climate and weather files are derived from historical data to December 2015. It is imperative for the NCC to accurately reflect real weather conditions. In a changing climate, this can only be achieved using regular updates that incorporate recent observations.
While it is challenging to justify changes to the NatHERS data – any change which creates an average impact of more than 0.2 stars in NatHERS ratings requires a burdensome Regulatory Impact Statement and/or a recalibration of the star-band thresholds – there is no reason for the accuracy of commercial building modelling to be held back on this basis.
Exemplary Energy offers representative data that incorporates the most recent years up to 2020 and soon plans an update that will incorporate all observations to the end of 2021.
The second and third issues will be discussed in forthcoming articles.
The issues outlined herein need to be considered by policymakers and modellers alike. We have advised our colleagues at CSIRO of these findings and will continue to work with them to avoid further propagation of the errors and offer our support to improve the data going forward. We urge policymakers to be mindful of these issues as modelling inaccuracies arising now are embedded in building operations for many years to come.
In the interests of full disclosure, we note that Exemplary Energy offers high quality climate and weather data, including ersatz future climate data, that avoid the issues of the CSIRO datasets. These are available for modellers demonstrating compliance through the JV3 pathway, along with non-regulatory applications in design and optimisation and resilience testing of buildings and energy systems.
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