As part of the ongoing investigation into our evolving climate, we routinely process and analyse meteorological data from successive years, conducting comparative assessments to reveal emerging trends and patterns.
Our previous temporal analyses only focused on examining variations in various weather elements with the results of EnergyPlus simulations of the three archetypes used in our Weather and Energy Index (EWEI), specifically targeting HVAC systems and heating and cooling dynamics within buildings. We have added the results of System Advisor Model (SAM) photovoltaic (PV) system simulations to enhance the comprehensiveness of our investigation up to 2023. The analysis for other capital cities can be viewed here.
Now, we are extending our previous temporal analysis to 2024 for all eight capital cities, so readers will soon be able to access our recent analysis on our blog.
For the analysis of weather elements, we examined the temporal variations in dry bulb temperature, humidity, wind speed, global horizontal irradiation (GHI), direct normal irradiation (DNI), and average precipitation. The analysis involved averaging these elements over three 15-year periods—1990-2004, 2005-2019, and the latest 15-year period from 2010 to 2024—and then comparing the results. A comparison between data from the latest 15 years, the data corresponding to the years and months specified in Industry Standard Meteorological Year (ISMY) files, and the data exclusively from 2024 was also undertaken. ISMYs were originally developed for application in house energy rating software used in NatHERS and derive from historical Bureau of Meteorology (BOM) weather data spanning from 1990 to 2015. Over time, they have become the industry’s de facto standard. It is therefore important to compare against ISMY data, as it provides a reference to gauge alignment with established benchmarks and understand the significance of temporal variations in weather elements.
First of all, we compared 2024 weather data with 2023 data. Overall, summer months (December-February) had higher temperatures (0.62°C), less humidity (0.56g/kg) and higher GHI and DNI (2.48 Wh/m2 and 0.2Wh/m2), while winter months (June-August) had lower temperatures (0.56°C), less humidity (0.03g/kg), less GHI and DNI (4.34 Wh/m2 and 5.65Wh/m2). Also, overall, 2024 shows a different precipitation pattern with 2023 in most months but few months had big differences (88.6mm in January, 52mm in July and -32.8mm in December).
Comparing 1990-2004 with 2010-2024 showed an increase in Melbourne’s mean temperature of 0.27°C (1.74%), an increase in moisture of 5.98%, and a small decrease in wind speed of 1.66%. GHI had a high increase of 5.35%, and DNI had an increase of 0.29%. Meanwhile, comparing 2005-2019 with 2010-2024 showed a decrease in the mean temperature of 0.24°C (1.51%), an increase in moisture of 2.78%, a decrease in wind speed of 2.93%, and an increase in GHI of 2.26% while a decrease in DNI of 3.66%. The small decrease in mean temperature and increase in GHI for 2005-2019 vs 2010-2024 is likely a result of 2005-2019 experiencing comparatively higher annual average dry bulb temperatures when compared to other years.
Average precipitation in 2010-2024 was 2.35% lower than in 1990-2004, and 11.51% higher than the 2005-2019 period. When comparing monthly averages, the gap between 2010-2024 and 2005-2019 varies from 51.89% in January to -21.71% in February. These big differences will affect building simulation model results for heating and cooling.
Compared to the ISMY period (1990–2015), the most recent 15 years (2010–2024) show notable climate changes: mean temperature decreased by 0.03°C (0.17%), moisture rose by 4.49%, and wind speed grew by 0.36%. Additionally, GHI increased by 4.09%, while DNI decreased by 2.14%. Average precipitation also rose by 13.67%. These shifts highlight distinct climatic trends between the two periods.
The annual trends of energy consumption reveal intriguing patterns across various building archetypes. All archetypes had increasing trends for cooling energy consumption from 1990-2024 and 1990-2004 as well as in the 26-year period of 1990-2015 still in widespread use for building simulations despite the significantly warmer subsequent decade, while showing a decreasing trend in 2005-2019 and 2010-2024. In contrast, heating energy consumption followed an opposite pattern with decreasing trends for all archetypes in 1990-2024, 1990-2004 and 1990-2015 periods, but increasing trends in 2005-2019 and 2010-2024. These trends are indicative of a changed climate and highlight the importance of using relevant climate files from the more recent 2010-2024 period in building energy simulations rather than the older ISMY data.
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