The value below which a specified percentage falls (described in UKCP09 as probability level).
UKCP09 projects changes in climate in several ways, and some outputs involve percentiles / probability levels. The UKCP09 probabilistic projections make use of percentiles / probability levels to express the likelihood of changes being greater than or less than a certain amount. See the page on probabilities in UKCP09 for how to interpret these percentiles / probability levels.
For sea level and storm surge height projections, the use of percentiles represents only the percentage of model simulations that give values less than or equal to that percentile, and contain no information on the probability or frequency of exceedance of that value. For example, the sea level rise 90th percentile value is one that exceeds the sea level rise projected by 90% of climate models.
- 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.