Local downscaling of temperature projections for energy planning purposes in an Alpine area
Authors: Zardi Dino , Laiti Lavinia , Giovannini Lorenzo 
Published: March 2022

&lt;p&gt;Medium- and long-term energy planning at regional scale requires, among others, the estimate of the future energy demand driven by expected&amp;#160; heating and cooling needs of buildings, according to the local impact of changing climate. To support the development of the 2021-2030 Energy Plan of the Province of Trento in the Alps, temperature projections provided by EURO-CORDEX Regional Climate Models (RCMs) were downscaled at 11 weather stations, representative of altitudes between 0 and 700 m a.m.s.l., to estimate the future values of a set of parameters that are commonly used to model the energy demand of buildings, such as: Heating and Cooling Degree Days (HDDs and CDDs), Test Reference Years (TRYs) and Extreme Reference Years (ERYs). A dataset of temperature and solar radiation hourly measurements, taken at the stations starting from 1983, was quality-controlled and analyzed to estimate statistics and observed trends for both variables, as well as degree days, reference years and climate change indices from the ETCCDI set. A hybrid downscaling approach (combining statistical and dynamical techniques) is then applied to temperature projections, based on the application of the &lt;em&gt;morphing method&lt;/em&gt;&amp;#160;to&amp;#160;the results of&amp;#160;an ensemble of&amp;#160;16 RCMs, allowing the estimate of&amp;#160;future TRYs, ERYs&amp;#160;and degree days&amp;#160;in 2030 and 2050&amp;#160;at the selected sites&amp;#160;(notice that&amp;#160;no significant variation associated with climate change&amp;#160;was&amp;#160;assumed for solar radiation).&amp;#160;According to historical observations&amp;#160;(1983-2019), the warming tendency for monthly mean temperatures is clear and falls&amp;#160;around&amp;#160;0.06&amp;#160;&amp;#176;C&amp;#160;year&lt;sup&gt;-1&lt;/sup&gt;, slightly higher than reported at national level. The increase is more pronounced in spring and summer than in autumn and winter, with minima in December and especially May.&amp;#160;No significant trend is observed&amp;#160;for solar radiation trends.&amp;#160;As for HDDs, stations at different altitudes show comparable reductions, of around&amp;#160;-10 HDDs&amp;#160;year&lt;sup&gt;-1&lt;/sup&gt;,&amp;#160;with an apparent tendency to accelerate in the most recent years.&amp;#160;The increase of CDDs can be quantified in less than&amp;#160;5 CDDs&amp;#160;year&lt;sup&gt;-1&lt;/sup&gt;.&amp;#160;The ensemble of temperature projections estimate temperature increases of 0.5 &amp;#176;C between 2016 and 2030 and 1.3 &amp;#176;C between 2016 and 2050 on average (0.03-0.04&amp;#160;&amp;#176;C&amp;#160;year&lt;sup&gt;-1&lt;/sup&gt;),&amp;#160;implying further future reductions of HDDs (between -4 and -11% at 2030, between -10 and -21% at 2050) and increases of CDDs (between 12 and 36% at 2030, between 36 and 87% at 2050). Such changes will&amp;#160;correspond&amp;#160;to major modifications in the&amp;#160;seasonal profile&amp;#160;of&amp;#160;the&amp;#160;energy&amp;#160;demand associated with the winter heating and summer cooling of buildings in the Alpine area.&lt;/p&gt;