Step 2: Consider the possible behavior of each contributing factor

Each factor has a range of potential behaviors. For example, climate could range from nearly no change (assuming low greenhouse gas emissions and strong dampening feedbacks) to large changes (assuming high emissions and strong amplifying feedbacks), sensitivity could range from no sensitivity (physical, biological, and social systems immune to climate changes) to high sensitivity (systems heavily disrupted by even small changes in climate), and human dependence could range from no dependence (substitutes for disrupted systems readily available) to complete dependence (no substitutes available). 

An illustrative example: The societal consequences of climate change due to agricultural impacts

How might each of the contributing factors behave?

Let’s allow each factor to take on only one of three possible discrete values that capture the full ranges: low (L), moderate (M), and high (H).

Four plausible distributions for the contributing factors span a useful range to consider: uniform, centered, leftward, and rightward. In a uniform distribution, the three potential values (low, moderate, and high) are equally likely. In a centered distribution, moderate values are most likely with low and high values less likely. In a leftward distribution, low values are most likely and moderate and high values are less and least likely, respectively. Finally, in a rightward distribution, high values are most likely and moderate and low values are less and least likely, respectively. Of course, other distributions (e.g., bi-modal) are possible, as are variations on the distributions considered here (e.g., changes in the mean, standard deviation, skewness, etc.). However, the four distributions we include here span a broad range of plausible assumptions for the potential behavior of the contributing factors.

Societal consequences due to agricultural impacts

An illustration: The societal consequences of climate change due to impacts on agriculture