Sampled data

Sampled data is one of the outputs associated with the UKCP09 climate change projections. Sampled data is available from the climate model emulator, consisting of 10,000 equally probable estimates of change or absolute future climate for UKCP09 climate variables in a given batch, at a particular grid cell or aggregated area, for a given temporal average, time period, and emissions scenario.

In detail

Production of the probabilistic projections involves the use of a climate model emulator, which has been trained on the 280 member PPE. Sampled data consist of 10,000 samples from the initial 1,000,000 model emulator samples. These 10,000 samples are selected based on their weighting with respect to observations and Braganza indices. Each of the 10,000 samples is the output from one emulated model variant and also takes account of the discrepancy term. The statistical nature of the emulator means that there can be multiple entries in the 10,000 samples that originate from the same model variant.

• Sampled data is explained in more detail in the Reports & guidance section. It is important to recognise the difference between sampled data and CDF data.

• More information about Sampled data is given in Appendix 4.2 of the UKCP09 Climate change projections report.

• An overview of how probabilistic projections are created and presented in UKCP09 is described in Box 3 of the UKCP09 Briefing report. More details are provided in Chapter 3 of the UKCP09 Climate change projections report, including an overview of the methodology in Section 3.2.12 and discussion about the interpretation of UKCP09 probabilistic projections in Section 3.3.

• A discussion of sources of uncertainty in the UKCP09 probabilistic projections is available in Annex 2.4.

• Some worked examples were developed prior to the launch of UKCP09 that used dummy outputs to examine how the UKCP09 probabilistic sampled data might be used. The worked examples should not be interpreted as a best practice method for using UKCP09, but as one way of using the outputs.

• A selection of inappropriate uses of the UKCP09 probabilistic projections is also provided.