Customisable maps in detail
This page gives more information about when it is appropriate to use customisable maps, some things to be aware of when using them and details about how the maps show uncertainties in the projections.
The customisable maps are a useful way to display climate projection information in certain circumstances. You might like to use the maps:
· To show the spatial pattern of projected changes at a given probability level
Customisable maps allow projected changes to be presented for the UK as a whole or for a selected administrative region. This is useful to investigate the relative risks posed by projected changes across the UK.
Maps are particularly useful tools for communicating climate projections to a wide audience.
· To show spatial variations in the amount of uncertainty
For each mapped 25 km grid square, a map will show the projected change associated with a certain probability level.
For each grid square, the maps show the value (e.g. temperature change) for which there is a given relative probability of the change being below that value. So for example, if you produce a map showing temperature change for the 2050s at the 10% probability level, then a grid square showing 1˚C would indicate that in that 25km area, there is a 10% probability (very unlikely) that temperatures will rise by less than 1˚C.
The values indicated for each grid square are a reflection of the contributions of the various sources of uncertainty for that grid square. These uncertainties are different for each grid square. The model variant that provides the value at a given probability level may therefore be different for different squares. As a result of this the values depicted across a given map are not necessarily spatially coherent. This means that it is not possible to aggregate the projections for multiple grid squares.
Understanding the level of uncertainty associated with each 25 km grid square may be helpful to inform the use of projections from two separate locations. Different strategies might be required to manage the different uncertainties represented by each grid square. It can also be used to assess confidence in the projections for any specific location, by comparing the width of the uncertainty ranges in neighbouring grid squares.
When using customisable maps for specific tasks there are some things that you should be aware of. Some common uses of the maps are shown below with details of things to bear in mind for each one.
· Using maps to show the probabilistic range of climate change at a given location
A single customisable map can only show the projected changes associated with a single, user-defined, probability level. This means that by presenting a single map in isolation, the full range of possible climate outcomes could easily be overlooked. It is important to recognise that maps produced with different probability levels and emissions scenarios will provide different projections of future changes.
If a single map (and therefore a single probability level) is used, it should be clearly stated which has been used and why, and recognised that this choice will constrain the range of future climate outcomes that are considered.
In order to show a more complete spread of climate projections it is advisable to use several maps showing different probability levels.
· Using maps to assess the evolution of changes through time
A single customisable map shows the projected climate change associated with a single, user-defined, future 30-year time period. As such, they provide no information about the evolution of changes through time.
UKCP09 provides future climate information for static 30-year time periods, yet information about transient changes is sometimes required for impacts and adaptation assessment. An estimate of transient changes can be obtained through comparison of multiple maps (i.e. Maps for each 30-year time period).
A more convenient visualisation is provided by a CDF which shows on one graph the projected evolution of climate change through time at different probability levels for a single location based seven future 30-year time periods.
If fully transient information is required, the 11-member RCM output, available through the BADC website , provides transient changes for the UK from January 1960 to December 2099, with a daily time-step. However, as this output is not part of UKCP09 it may not be consistent with the UKCP09 probabilistic climate projections and cannot be visualised or delivered through the User Interface .
· Using maps to visualise probabilistic projections for aggregated areas
UKCP09 provides climate projections for certain pre-defined aggregated areas. However, these projections cannot be visualised on a customisable map using the UKCP09 User Interface.
Maps that show projections for administrative regions in the UK are available however, from the Maps & Key Findings page.
· Using maps to evaluate the joint probability of changes in more than one variable
Customisable maps provide information about projected changes in one variable (such as temperature or precipitation) based on CDF data. Due to the nature of this underlying data, customisable maps cannot be used to provide coherent climate storylines across variables (i.e. simultaneous changes for different variables) for a certain probability level.
For example, it is not possible to assume that the changes in summer temperature associated with the 90% probability level will be accompanied by the summer precipitation changes also associated with the 90% probability level. This is because the model variants that indicate a large increase in temperature might not be the same ones that indicate a large increase (or decrease) in precipitation. In this way, customisable maps for different climate variables need to be considered independent of each other.
Where information on joint probability is required, users should use joint probability plots and the joint probability functionality within the UKCP09 User Interface. There are limitations as to how and for which variables joint probabilities can be explored (see Joint probability plots for more details).
· Using maps to present the spatial distribution of projected climate change
For each grid square, UKCP09 maps show the projected change for which there is a given relative likelihood (e.g. 90% probability level) of the change being at or below that value.
For example, consider a UKCP09 map showing grid square values at the 90% probability level of a change in summer mean temperature for the 2080s under a high emission scenario. In this example, the value indicated in each grid square is that at which the evidence suggests there is a 90% probability of the projected mean summer temperature being below for that grid square (see Section 4.3.1 of the Climate Change Projections report).
Customisable maps are created from the CDF data, which reflect the known uncertainties considered in the UKCP09 methodology (See the Projections report, Chapter 2). More information about uncertainty in the climate change projections see the 'Climate Change Projections: Uncertainties' page.
A single customised map shows projections associated with a single, user-specified, probability level. A single map does not represent the uncertainty across the projections for each grid square. Multiple maps are needed to illustrate the uncertainty across the projections.
The Maps and Key Findings pages present maps in groups of three to show the projected changes at 10%, 50% and 90% probability levels. This is done for illustrative purposes only. The use of these three probability levels should not be seen as best practice as other probability levels may be more important for certain applications.
As a general guideline it is suggested that customisable maps for the 10% to the 90% probability levels are useful to support decision-making. Outside the 10% to 90% probability range, care should be exercised when using the maps as the robustness of the projections decreases considerably.