Search site

Before you start using UKCP09...

UKCP09 climate projections are based on sophisticated scientific methodologies. Before you begin to use the UKCP09 projections, there are eleven things that it is useful to understand about the data and the way it is presented.

1 - Use the information that's right for you

UKCP09 presents climate projection information in a number of ways. These range from simple maps, graphs and key findings to more complex customisable outputs and technical reports. A large sample set of plausible climate scenarios has been used to create the maps and charts. To find the information that is right for you please visit the 'What do you want to do?' page.

2 - Don't use UKCP09 in isolation

UKCP09 should be seen as a vital resource that can be used to support climate adaptation planning and research. It provides climate projection data for the UK and its regions. However, UKCP09 on its own will not necessarily provide all the information you need to plan and adapt to climate change and its impacts. To find out more about assessing vulnerability to climate change and identify potential adaptation plans see  the  UKCIP Adaptation Wizard and other adaptation support  resources .

3 - UKCP09 provides projections not predictions

UKCP09 provides projections of the future climate that are based on the current understanding of the climate system. The results are called "projections" rather than "predictions" because the results are conditional on certain assumptions that cannot be quantified, such as the likelihood that an assumed pathway of future emissions of greenhouse gases will turn out to be correct.

The UKCP09 land projections are presented as probability distributions, rather than as single values, in order to represent the uncertainty in potential future changes in climate.

For more information on probability in the UKCP09 projections please see the 'Probability in UKCP09' page.

4 - Maps are best for communicating messages, not for making decisions

Maps give a good visual impression of how climate might change in the future, but need to be interpreted and described carefully. Rather than show just one map, it is best to show a series representing a range of possible impacts.

For example, presenting a series of maps at the 10%, 50% and 90% probability levels, will show the range of outcomes - temperature changes are very unlikely to be less than those shown in the 10% map and very unlikely to be more than those shown in the 90% map. It is important to note that the maps do not imply that the same probability level change will happen everywhere at the same time.

For more information on probability in the UKCP09 projections please see the 'Probability in UKCP09' page.

5 - Projections in the 10-90% probability level range should be used for decision-making

The UKCP09 projections are presented as probability distributions, but we have limited confidence in the extreme values from these distributions. The extreme values are particularly sensitive to the precise methodology used to construct the scenarios that are used to create the probability distributions.

It is therefore strongly recommended that the 10% and 90% probability levels are used to represent low and high changes in climate. For sea level, the 5% and 95% probability levels should be used.

For more information on probability in the UKCP09 projections please see the 'Probability in UKCP09' page.

6 - Take care when comparing or combining climate variables

The UKCP09 projections show changes in several climate variables, such as temperature and precipitation, but not all combinations of changes in different variables or at different times of the year are plausible. You can use the User Interface  to produce joint probability plots showing changes in two variables (such as change in temperature and precipitation) or two seasons (such as change in winter precipitation and summer precipitation).

If you want to look at coherent changes in more than two variables or times of the year, you need to use the underpinning sampled data.

7 - Projections are presented for three possible emissions scenarios

To make projections of future possible climates, assumptions had to be made about levels of future emissions of greenhouse gases. A number of emissions scenarios were developed by the Intergovernmental Panel on Climate Change (IPCC) which reflect changes in the way economies are structured, population grows, technology develops, as well as energy intensity and land use changes. 

The UKCP09 projections over land and marine areas are produced for three different emissions scenarios: Low, Medium and High (B1, A1B and A1FI). All should be assumed to be equally plausible. They are all "non-intervention" scenarios which do not assume specific policy measures to mitigate the effects of climate change.

For more information see Annex 1 of the Climate projections report.

8 - The marine projections are different in nature from those over land

UKCP09 provides probabilistic projections of atmospheric variables over marine areas. These are distinct from the marine projections which describe changes in marine variables such as sea temperature, salinity, wave height and ocean circulation patterns.

The marine projections are less well developed than the UKCP09 projections over land and marine areas. Many of the marine projections are based on a single emissions scenario (A1B); three emission scenarios are only considered for mean sea level. Only mean and extreme (surge) sea levels projections consider different time periods. The original shelf seas projections also do not consider uncertainty, although this will be addressed in future updates.

For more information on the marine projections see the Marine and coastal projections report.

9 - Finer modelling resolution does not give greater confidence

The process of downscaling, where data from a large spatial scale model is reduced to smaller, more local scale, increases the uncertainty of the outcome.

The UKCP09 Weather Generator, although at 5 km resolution, does not contain any more climate change information than is available in the 25 km projections because the future sequences of climate are generated from the 25 km projections. The 5 km grid does contain more topographical detail though, which may be important for some users.

10 - The Gulf Stream, carbon feedbacks & aerosols are considered

Climate model studies show a reduction in the future strength of the Meridional Overturning Circulation (MOC), more commonly known as the Gulf Stream. Current models do not suggest a complete collapse of the MOC, but different models suggest different levels of weakening. These uncertain effects of a gradually weakening Gulf Stream are included in the UKCP09 projections. See Annex 5 of the for more information.

The impacts of carbon cycle feedbacks and aerosols on the climate system have also been taken into account. For details of the climate feedback processes included in UKCP09, see sections 3.2.5 and 3.2.6 of the Climate Projections report.

11 - Uncertainty around climate projections varies depending on the climate variable and time period.

UKCP09 provides sound science, but the limits of our current ability to understand and model the climate system lead to some climate variables being predictable with greater confidence than others. For example, there is relatively high confidence in projections of temperature, and less confidence in variables such as summer precipitation or cloudiness.

For more information please see the 'Handling uncertainty in UKCP09' page.

Need more help?

  • For more details about the UKCP09 climate projections, please see the Climate Change Projection Report in the Reports and Guidance section.
  • For examples of how other organisations have used UKCP09 projections please see the Case studies.
  • For other queries please see our Help tab.