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Medium emissions scenario

The middle of the three emission scenarios used in UKCP09, referring to the SRES A1B emissions scenario.

In detail

In UKCP09, projections are developed under three different emissions scenarios, two of which come from the A1 storyline, and one from the B1 storyline, developed in SRES. Within UKCP09 the emission scenarios are labelled based on their relative greenhouse gas emissions levels:

  • High (SRES A1FI)
  • Medium (SRES A1B)
  • Low (SRES B1)

These comprise a wide range but not the full set of SRES emissions scenarios.

An emissions scenario is one of the elements required when building a request in the UKCP09 User Interface.

  • The implications of user choices are discussed in Section 4.4 of the UKCP09 Climate change projections report.
  • More information about the emissions scenarios that were used in the preparation of the UKCP09 projections is given in Section 3.2.13 of the UKCP09 Climate change projections report and in Annex 1. Further details about the uncertainties associated with emissions scenarios are provided in Section 2.4 of the UKCP09 Climate Change projections report.

One of the advances in UKCP09 is that realisations of time-dependent climate changes for the 21st century were obtained for all three emissions scenarios reported ( A1B1, B1 and A1FI), making the final results more robust than those presented in previous UK climate scenarios. However, constraints associated with the experimental design (such as that the discrepancy term for future projected variables was assumed to be the same for all three emissions scenarios as obtained using A1B1) mean that the results for B1 and A1FI are considered less robust than those for A1B1.

It should be remembered that different UKCP09 use one or more of these emissions scenarios. In addition, a has been developed to explore a high-end, very unlikely, scenario for sea level rise.

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