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What these maps show ...

Above we show two variables – temperature and precipitation (includes rainfall, snow and hail). We show changes suggested by climate models at the 10, 50 and 90% probability levels. Our example considers the impact of continued global greenhouse gas emissions on a pathway that is described, in UKCP09, as the medium emissions scenario.

• The 10% probability level maps tell us that the probability that the change will be less than that shown is 10% – we use the term very unlikely to be less than to describe this.
• The 90% probability level maps tell us that the probability that the change will less than that shown is 90%. In other words, the change is very unlikely to be greater than shown.
• The 50% probability level maps tell us that the strength of evidence for the projected change is just as likely to be greater than the values shown, as it is to be less than the values shown – we call this the central estimate. It is not necessarily the most likely projection.

Together, a set of maps, like those above, can show us a plausible  range of projected changes for different times in the future at particular locations (for example, a grid square) for a given emissions scenario.

Maps like this are helpful when thinking about different options for adaptation to climate change, as they allow users to look at the relative risk of different degrees of climate change, and weigh these risks against what is needed to put in place effective adaptation measures. In other words, they require users to think about the level of risk they need to manage.

• These maps show the changes at the 10, 50 and 90% probability levels. UKCP09 has information on the changes outside this range (e.g. at the 5% probability level) but these projections are less robust and should be used with great caution.

Why are some land areas not covered by the grid squares?

All 25 km grid squares are defined as land or sea, based on whether a majority of their area consists of land or sea. This inevitably means that some coastal locations of the UK are not included within land grid cells. Where this occurs, the nearest land grid cell to your location should be selected; this still gives a robust result. It should also not be assumed that locations that do not have an overlying land grid square will be subject to inundation by the sea in the future as this is not the case.

How the maps should not be interpreted...

• The higher probability levels do not mean that there's more chance of the values shown at these levels being reached. For example, a 90% probability level of a temperature increase of 3°C does not mean that the probability of the temperature being 3°C is 90%. It means that the change to temperature is very unlikely to be more than 3°C: in other words, very likely to be less than 3°C. This is because these maps show cumulative probabilities – however UKCP09 does also provide information on the relative probabilities for change being anywhere over a range – say from 1 to 5ºC.

• The maps do not show a future climate forecast for the UK; they show a picture of the strength of evidence for different future climate changes.

• The maps do not show a snapshot of the future.  What this means is that if the future change in one particular grid square in one map shown above does actually happen, it does not mean that every other grid square across the country will also experience the same change shown in the same map at the same time.

• As with all probabilistic information, It is not possible to average information from different grid squares to get a result for a larger area. However, many people will be interested in regional results, so projections have been made specifically for larger areas, as well as at 25 km resolution. 

The UKCP09 technical site has more maps providing further projections for low, medium and high emissions scenarios and more climate variables (temperature, humidity, etc). 

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