Spatio-temporal analysis of heating and cooling degree-days over Iran

In this research, temporal trends and change points in heating degree-days (HDD), cooling degree-days (CDD), and their simultaneous combination (HDD + CDD) were analysed for a 60-year period (1960–2019) in Iran. The results show that less than 20% of the study stations had significant trends (either upward or downward) in HDD time series, while more than 80% of the stations had significant increasing trends in CDD and HDD + CDD time series. Abrupt changes in HDD time series mostly occurred in the early 1980s, but those in CDD time series were mostly observed in the 1990s. The cooling energy demand in Iran has dramatically increased as CDD values have raised up from 690 ºC-days to 1010 ºC-days in the last 60 years. HDD, however, almost remained constant in the same period. The results suggest that if global warming continues with the current pace, cooling energy demand in the residential sector will considerably increase in the future, calling for a change in residential energy consumption policies. Highlights Monotonic trends in HDD, CDD and HDD + CDD time series were analysed in Iran. The series were also analysed for possible change points using the non-parametric method. Energy demand for cooling houses increased, while that for heating houses remained constant. Up to three upward abrupt change points were observed in the annual CDD series.