Long-term trends in heating and cooling degree days at Mediterranean cities, in the context of climate change

Nowadays, the global climate change has important impacts on many aspects of human life such as agriculture, economy, health and energy consumption. The issue of climate change has concerned the scientific community as the solutions have to be direct and effective. Studies on energy demands under a climate change environment are particularly useful as they improve our understanding of the impacts of changing climate on energy sector. This research focuses on a very responsive to climate change area, the Mediterranean, and attempts to analyze the climate and energy demand trends, processing historical temperature records from weather stations at seven Mediterranean cities (Nicosia, Athens, Rome, Palma, Montpellier, Madrid and Seville) for the period of 1970 – 2018. Consecutively, cooling degree days (CDD) and heating degree days (HDD) have been estimated according to the given climatic data. These simple indicators are very useful as they point out the amount of energy demand, according to the deviation of a standard temperature value (threshold).

The research has shown a statistically significant increase in the ambient air temperature at all cities, ranging from 0.37 to 0.50 ⁰C per decade on annual basis, but with notably higher increasing trends in summer compared to winter.  Consequently, the energy demand for cooling interior spaces has increased as well.  On the other hand, there is a significant decrease of heating demand. Annual CDDs have increased at rates reaching up to 65 degrees per decade over the study period (Nicosia), while the rate of decrease in HDDs ranges approximately between 55 and 110 degrees per decade at the selected cities. The analysis has been conducted on different timescales (monthly and annual) in order to approach the optimal accuracy. 

 

Further, our results will be used to validate simulations of CDD and HDD from Regional Climate Models downscaled over the areas of interest for a reference period, while future simulations will be realized to find projected trends in CDDs and HDDs at the Mediterranean cities by the end of the century.