Scenarios are a decision making tool that policy makers can use to
model the range of possible consequences associated with particular
actions or events. The European Environmental Agency explains that
scenarios are "based on 'if-then' propositions" and are not intended to
be used as predictions or forecasts. These stories can help decision
makers explore assumptions, test hypotheses, and ultimately, develop
robust strategies capable of managing the irreducible uncertainties of
global environmental change. Although many types of scenarios exist
(i.e., high resolution scenarios, global climate model scenarios, and
analogue scenarios), scenario building
typically involves the following components:
1. Identifying a decision;
2. Describing the current state of affairs;
3. Describing any changes that are likely to occur; and
4. Describing the future consequences of those changes.
Additional information is available under "Environmental Scenarios" in the Recommended Links section.
Simple scenarios, such as those referenced in the
scenario tree, can be
useful in grappling with uncertainties in climate
adaptation decisions. If time and information were free, it would be
desirable to have complete, detailed forecasts of climate change
(downscaled to an appropriate location). However, in practice the range
of alternatives available in a given context are highly constrained and
there may be little value of information associated with more
detailed climate scenarios in selecting among these limited
alternatives. Hence, simple scenarios can help and should be the first
step in thinking through uncertainties for climate change.
Sockeye Salmon Climate Scenario
We recently conducted a workshop to help characterize and quantify how vulnerable sockeye salmon are to climate change in the Fraser River System. Two temperature change scenarios were employed during the event: 1) 2°C of additional warming over 60 years; and 2) 4°C of additional warming over 70 years. The 60 year period comprised 15 four-year lifecycles of sockeye salmon cohorts. These simple scenarios were deemed appropriate by the scientists participating in the workshop because they had little or no specific knowledge of how a warmer and wetter climate would affect the life cycle stages of sockeye salmon in this system.