The climate is changing, both globally and in the UK. To adapt effectively, engineers and planners need as much information as possible on how the climate will evolve. The UK Climate Impacts Programme (UKCIP) provided this in 2002 with UKCIP02 and the latest data UKCP09, which provides data to a resolution of 5 km square grids over the UK. Data sets from these were used in this study along with the historical measured data for three locations -Bracknell (London), Manchester and Edinburgh -to analyse critically the likely changes that may occur in the key climate variables, that is temperature, sunshine duration and solar irradiation. These parameters have an important bearing on the design and function of buildings and building services. Sunshine duration is the main variable that is used to obtain solar radiation in the UKCP09 5 km grid data. For the grids containing Bracknell, Manchester and Edinburgh, most of the UKCP09 data sets for the years 2050 and 2080 showed abnormally elongated sunshine duration, that is from sunrise to sunset, for clear days. In contrast, the latest historic measured data sets indicate only a third of the above sunshine duration. Note that the latter data are used in cooling load design calculations and for the generation of sol-air temperatures.1 Of particular note was the anomalous occurrence in UKCP09 of late evening sunshine duration. For Bracknell and Edinburgh, the sunshine duration at hour ending 20 and beyond showed substantial amount of predicted sunshine. As a result of this work, corrective action has been proposed for UKCP09 data. Furthermore, a very significant increase was also noted in solar irradiation for UKCP09. For the historic measured data for Bracknell, the clear day noon irradiation is 818 Wh/m 2 . For the UKCP09 grid containing Bracknell the 2080 High Emission scenario data gives an average value of 1002 Wh/m 2 , an increase of 23%. The same trend occurs for Edinburgh, (a present value of 789 Wh/m 2 and the predicted value of 948 Wh/m 2 , an increase of 20%). Note that compounded with presently found increase of 4-58C increase for the above locations, the substantial increase in irradiation will have a much more pronounced increase in the cooling load of buildings. An evaluation of the change in the character of solar radiation was also undertaken. This was done by noting the change in the diffuse fraction of global irradiation. For Bracknell and Edinburgh historic data and UKCP09 data 2080 High Emission data set show a drastic Address for correspondence: T. Muneer, School of Engineering and Built Environment, Edinburgh Napier University, Edinburgh EH10 5DT, UK. E-mail: t.muneer@napier.ac.uk Figures 1-8 decrease, respectively from 0.37 to 0.13 and from 0.33 to 0.14. Diffuse fraction may be used as an indicator of the prevailing sky clarity. If the predictions come true a drastic decrease in the diffuse fraction of this magnitude signifies a radical shift in the character of solar climate for the future. The current solar climate of Bracknell is known for its ab...

Hourly solar radiation data are required in many building services applications. These are also reported in the Chartered Institution of Building Services Engineers Guides A & J. Data from 16 locations in the UK were used to evaluate the so called Liu and Jordan model 1 for monthly averaged hourly solar irradiation. Individual data sets spanned periods from 12 to 26 years between 1968 and 1994, and overall, provided data from practically the full range of latitude of the UK (50.228N-58.138N). For hourly estimation, the model only slightly underestimated both global and diffuse radiation before noon and overestimated, again only slightly, after noon. In addition, a discrepancy was observed between the measured data and the model's predictions at low sunset angles. Following earlier research work, an attempt was made to further improve the Liu and Jordan model. However, it was found that at least for the UK data set, any such attempts were futile. This behaviour was attributed to the highly random nature of UK's solar climate. Practical applications: Most meteorological stations report solar radiation data on a daily averaged basis. However, most building energy simulation software requires hourly radiation. Research studies have confirmed that the well-known Liu and Jordan model, which enables the above conversion, performs well for locations in the US. This paper evaluates the above model for locations in the UK and compares it with previously studied Indian locations. According to the evaluation, the average accuracy of the model to estimate hourly radiation from its daily counterpart is 85%. Nomenclature LAT latitude (degree)n average daily hours of bright sunshine (h) N astronomical day length (h) r D ratio of hourly to daily diffuse radiation r DC ratio of computed hourly to daily diffuse radiation r D_LJ r D predicted by Liu and Jordan's regression model r Dn r D predicted by proposed new model r Dc,am ratio of computed hourly to daily global radiation before noon r Dc,ave average ratio of computed hourly to daily global radiation r Dc,pm ratio of computed hourly to daily global radiation after noon r Dm,am ratio of measured hourly to daily diffuse radiation before noon r Dm,ave average ratio of measured hourly to daily diffuse radiation r Dm,pm ratio of measured hourly to daily diffuse radiation after noon r G ratio of hourly to daily global radiation r GC ratio of computed hourly to daily global radiation r Gc,am ratio of computed hourly to daily global radiation before noon r Gc,ave average ratio of computed hourly to daily global radiation r Gc,pm ratio of computed hourly to daily global radiation after noon r Gm,am ratio of measured hourly to daily global radiation before noon r Gm,ave average ratio of measured hourly to daily global radiation r Gm,pm ratio of measured hourly to daily global radiation after noon Greek letters e percentage error (%) x hour angle (degree) x s sunset hour angle (degree)

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