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Definitions and climate scenarios basics

  1. A climate change scenario is:

    • a coherent, internally consistent and plausible description of a possible future state of the world [from Parry & Carter, 1998, and Parry, 2002], and
    • a plausible future climate that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change.. [from IPCC TAR, 2001].
  2. A climate change scenario is not a prediction of future climate!

  3. Why do we need climate change scenarios?

    • To provide data for Vulnerability, Impacts and Adaptation (VIA) assessment studies;
    • To aid strategic planning and/or policy formation;
    • To scope the range of plausible futures;
    • To explore the implications of policy decisions.

  4. What are the benefits of developing climate scenarios?

    • Simple to obtain, interpret and apply;
    • Provide sufficient information for VIA assessments;
    • Physically plausible and spatially compatible;
    • Consistent with the broad range of global warming projections;
    • Reflect the potential range of future regional climate change, i.e., be representative of the range of uncertainty in projections.
  5. DISTINCTION between a climate scenario and a climate change scenario (see IPCC, Chapter 13, 2001)

    • A climate change scenario = "a plausible future climate..." strictly refers to a representation of the difference between some plausible future climate and the current or control climate (usually as represented in a climate model, i.e. monthly/seasonal/annual values). This concept can be viewed as an interim step toward constructing a climate scenario;
    • A climate scenario = the combination of the climate change scenario and the description of the current climate as represented by climate observations (i.e. via a scrupulous analysis of the climate regime).

CLIMATE SCENARIO

=

CURRENT CLIMATE + CLIMATE CHANGE SCENARIO

Depending upon the study of interest, different temporal data must be used. For example, when considering extreme event changes and variability, daily data which can capture the changes of high frequency events of the climate regime must be explicitly taken into account.

Often the investigation of extreme events is of utmost importance for impacts and adaptation studies. However, most climate change scenarios derived from GCM output are generally based on changes in monthly or seasonal mean climate although recently, daily quantities of model output are being archived by climate modeling centres. Even though model output is being made available at finer temporal resolutions, it does not mean that it is any more meaningful than the output at monthly or seasonal time scales.

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