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Assessing the differences - UKCIP02 & UKCP09

UKCP09 reflects advances in our understanding and modelling of the climate system. The climate projections in UKCP09 supersede the scenarios from UKCIP02, the previous set of climate change information. Although many of the projected changes are broadly similar in nature, UKCP09 incorporates scientific advances that may have significant implications for projects or decisions made using UKCIP02. It is strongly recommended that users no longer employ UKCIP02 in new projects.

However, there are many existing projects and/or decisions that are based on UKCIP02 scenarios. Users should assess the robustness of their previous findings to determine if earlier assessments should be repeated using the new projections. UKCIP and the Adaptation Scotland have written a guidance note which provides background information for users who need to evaluate earlier work that used UKCIP02.

For a more detailed examination of the differences in methodology and data, please refer to the UKCP09 Climate change projections report Chapter 2, and Section 4.3.11.

Major changes adopted in UKCP09 projections include:

  • the explicit effects of land and ocean feedbacks;
  • uncertainty due to ;
  • modelling uncertainty: UKCP09 is derived from ensembles of climate models;
  • uncertainties associated with the statistical processing;
  • a change from 50 km to 25 km grid squares;
  • UKCIP02 used of an A2 scenario in 2080s with no separate treatment for response to aerosol and greenhouse gas forcing;
  • a change in some of the emissions scenarios used.

UKCIP02 should not be seen as a benchmark against which subsequent work must be compared. It may be useful to compare the two sets of projections as a first step in verifying the validity of existing assessment or decisions.