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The term 'uncertainty' refers to a state of having limited knowledge. Uncertainty can result from lack of information or from disagreement over what is known or even knowable.

Uncertainty may arise from many sources, such as quantifiable errors in data, or uncertain projections of human behaviour. Uncertainty can be represented by quantitative measures or by qualitative statements.

In detail

Uncertainty in climate change projections is problematic for those planning to adapt to a changing climate. Uncertainty in projections of future climate change arises from three principal causes:

  1. Natural climate variability;
  2. Modelling uncertainty, referring to an incomplete understanding of Earth system processes and their imperfect representation in climate models; and
  3. Uncertainty over levels of future greenhouse gas emissions.

UKCP09 is more advanced than previous UK climate scenarios in that it attempts to quantify uncertainties using probabilistic projections.

Find out more

  • An overview of the uncertainties associated with climate modelling is described in section 3.1 of the Briefing report.
  • More details about uncertainties are provided in chapter 2 of the UKCP09 Climate change projections report. A discussion of sources of uncertainty in the UKCP09 probabilistic projections is available in Annex 2.4 of the same report.
  • IPCC Fifth Assessment Report, Chapter 11 of the Working Group 1 report The Physical Science Basis.