UK Climate Projections - Reports & guidance: Online climate change projections report 4.3.1 Interpreting maps

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	Reports & guidance About the UK climate change projections Online Climate change projections report Summary 1 Introduction & overview 2 Why do we need probabilistic information? 3 The construction of probabilistic climate change projections 4 Probabilistic projections of seasonal climate changes 4.1 Probabilistic projections as PDFs & CDFS 4.2 Key findings 4.3 Maps of changes in seasonal climate 4.3.1 Interpreting probabilistic maps 4.3.2 Changes to seasonal mean temperature 4.3.3 Future seasonal mean temperature 4.3.4 Changes to marine seasonal mean temperature 4.3.5 Changes to summer mean daily maximum temperature 4.3.6 Changes to the warmest day of the summer 4.3.7 Changes to seasonal mean daily minimum temperature 4.3.8 Changes to annual & seasonal precipitation 4.3.9 Changes to the wettest day of winter & summer 4.3.10 Other variables 4.3.11 Comparisons with UKCIP02 4.4 How are probability distributions influenced by user choices? 4.5 Probabilistic projections changing with time 4.6 The joint probability of the change in two variables 4.7 Corresponding changes in global mean temperature 4.8 Variables for which probabilistic projections cannot be provided 5 Projections from the ensemble of regional climate models Annexes Download & ordering page	4.3.1 Interpreting maps of probabilistic climate change Many users of the UKCIP02 projections will have become used to looking at maps which show a snapshot of the distribution of changes in climate over the UK, for example those showing change in summer precipitation by the 2080s, for a High emissions scenario, at a resolution of 50 km. The UKCP09 maps which are shown in this Chapter have the same sort of appearance as those in UKCIP02, apart from the increased resolution of 25 km, but the nature of their content is quite different. The maps in this Section show changes at the 10, 50 and 90% probability level, taken from the cumulative distribution functions, CDF, at each 25 km square. Figure 4.3 shows a map generated by the User Interface, of projected changes in mean winter precipitation at the 90% probability level, over Wales. Values of percentage change are overprinted on each 25 km square; there is a 90% probability of the precipitation change being below this value. Shown alongside are the CDFs for two of the individual squares in that region, showing correspondence between the 90% probability level on the CDF and the value given on the map. So, for example, the upper CDF for an inland square shows that the projected change is very unlikely to be greater than 19% or, alternatively, very likely to be less than 19%. The lower CDF shows the very different change, 80%, at the same probability level, at a coastal grid square. The same principle will, of course, apply to maps showing projected changes at 10% and 50% probability levels.

		Figure 4.3: Relating a the map of changes, at 90% probability level, to mean winter precipitation over Wales by the 2080s under High emissions, to the CDFs of change at two of the 25 km squares.


		The values of change at a particular probability level (for example, 90%) for a number of grid squares cannot be averaged together; for this reason projections in UKCP09 are also given over two sets of larger areas (administrative regions and river basins). In addition, values of change at a particular probability level (for example, 90%) for two different variables (for example, mean temperature and precipitation) at a particular grid square, cannot be combined; this is the reason that joint probability values are made available (see Section 4.6). The maps shown in this Chapter have been produced directly by the User Interface, although they have been grouped together offline. In addition, the User Interface allows users to zoom in on particular regions of the UK (as in Figure 4.3 above) where each 25 km square can be overprinted with the value of change for that square. Previous Next

Last Updated Monday, 14 June 2010

4.3.1 Interpreting maps of probabilistic climate change