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How do the projections in UKCP09 compare with those in UKCIP02?

Although there are good scientific reasons why they should not be expected to be the same, an attempt is made to compare from UKCIP02 and UKCP09 in the Climate Projections report.

In detail

It is difficult to perform a comparison with UKCIP02 due to two reasons. Firstly the UKCP09 projections are probabilistic in nature whereas UKCIP02 gave a (single) projection. The only way to get around this problem is to compare the 50th percentile of the UKCP09 projection with the UKCIP02 projection. But this is not strictly a correct comparison. Secondly, the UKCP09 and UKCIP02 projections utilise different emission scenarios. UKCIP02 had four emission scenarios whereas UKCP09 has three emission scenarios. This difference results in it only being possible to compare the projections for each of the common high and low emission scenarios.

The differences between the modelling techniques employed in UKCIP02 and UKCP09 are expressed in this table.

Feature UKCIP02 UKCP09
content/view/711/690/ 2020s, 2050s, 2080s
7 decadal overlapping 30 year time slices from 2010 to 2099
Spatial resolution 50 km grid 25 km grid
Temporal resolution Daily, monthly seasonal, annual Daily, monthly, seasonal, annual

Weather generator for daily output

Aggregation UK level UK

English administrative regions

Devolved administrations

River based regions

Modelling approach and quantification of uncertainty Single UK model (HadCM3)

4 emissions scenarios

Ensemble approach: model parameter uncertainty explored in HadSM3, using perturbed physics experiments (PPE).

PPE used to construct a statistical emulator from which a greater range of variability in the climate model parameters can be considered.

Additional IPCC climate models included (MME) (model uncertainty).

3 emissions scenarios: low (B1), medium (A1B), and high (A1FI).

Statistical framework used to produce probabilistic projections, users will have a probability associated with each projection.

Outputs Single mean value of projections of 15 climate variables Probabilistic projections of same climate variables as UKCIP02.

Observed trends in recent climate.

Marine projections

Delivery UKCIP02 report

Maps, underlying model output

3 science reports: land, marine, historical trends.

Web-based User Interface to provide customisable output.

Climate model output and associated probability.

Dedicated website.