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Inappropriate uses of UKCP09 probabilistic projections

Limitations on the use of each product are identified in the reports and guidance – users should understand these prior to deciding which information to use.

The following are inappropriate uses of UKCP09:

  • For current and near-term vulnerability & impacts assessments

The first 30-year time period provided is the 2020s (2010–2039), the baseline period is 1961–1990 – therefore there is no information covering the period in-between.

Further reading

  • Probabilistic forecasts of near-term climate change based on a resampling ensemble technique. Räisänen, J. and Ruokolainen, L. 2006. Tellus 58A, 461–472 (2006).
  • Probabilistic forecasts of near-term climate change: sensitivity to adjustment of simulated variability and choice of baseline period. Ruokolainen, L. and Räisänen, J. Tellus, 59A, 309–320. (2007).

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  • Using only the central estimate from the probabilistic distribution

Users should not limit their considerations to a single value. There is no special significance associated with the or value identified as the most likely within the . An adaptation strategy that addresses the climate risks associated with a single projection leads to acceptance of a higher risk than necessary. Users should consider strategies across the probabilistic projections which would allow development of resilient and adaptive strategies that recognise the levels of uncertainty.

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  • Interpreting the UKCP09 maps as weather maps

UKCP09 maps for each grid square show a value based on a given relative likelihood (probability level) of the change being at or below that value.

These values take into account the various sources of uncertainty for that grid square and will vary from one grid square to another.
The projected change of a variable at a particular location does not mean that the change for other variables at that location will be the same, nor does it mean that the change at other locations for that variable will also be at that probability level. The relationships between projected changes can be seen in joint probability plots.

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  • Comparing a seasonal/monthly mean from a single year with that of a 30-year mean

A single season or year does not represent a 30-year averaging period.

  • Averaging probabilistic projections for different grid squares to produce values for a user-defined aggregated area

The UKCP09 data sets ( and CDF data) are not spatially consistent across adjacent grid squares.

Pre-defined aggregated areas of administration regions and river basin districts (see Section 1.2.1, Climate change projections report) and marine regions (see Section 4.3.4 in the Climate change projections report) have been derived and are the only aggregated areas larger than a single grid square available.

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  • Averaging CDF data for different temporal averaging periods

The CDF data for a given grid square are not temporally consistent  (e.g. month to month, season to season, or one 30-year period to the next) so cannot be averaged to form a single CDF data set for a combined temporal averaging period (multiple months other than seasons provided or multiple seasons).

  • Exploring transient future climate or changes throughout the 21st century

The projected UKCP09 climate outcomes are an average for that 30-year period (monthly, seasonal and annual averages), depicting a stationary 30-year climate. Users should not combine the data from multiple 30-year time periods to create a single data set to assess impact, risks and adaptation options across multiple 30-year time periods.

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  • Overlaying GIS shapefiles for more than one variable

The GIS Shapefiles were created using the CDF data, hence two variables overlayed in GIS will not relate to each other (see above).

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