How to interpret agreement on sign of change?

The agreement on sign of change is a confidence metric based on the number of models agreeing on a decrease, no change or an increase in the climate change signal of a particular climate impact indicator. The more models that agree on a sign of change, the more confident one can be about the sign of change. For every grid point, the confidence level for the dominant sign of change is indicated, i.e. the sign of change that has the highest number of models agreeing on that sign of change. 

 

In detail, there are two steps involved (see Figure 1 for an exemplary explanation). First, the numbers of models showing a particular sign of change (decrease, no change, increase) is estimated. The sign of change with the highest number of models is defined the dominant change type.

Second, the number of models agreeing on the dominant change type is classified into 4 confidence levels:

  • Few: 7-10 models agree on type of change
  • Some: 11-14 models agree on type of change
  • Many: 15 or more models agree on type of change
  • Unclear: No dominant change type can be estimated
Sign of Change

Figure 1 Exemplary explanation of how the confidence level of the agreement on sign of change is estimated. The four colours relate to the type of change: blue (increase), yellow (no change), red (decrease) and grey (unclear, no dominant change type). The strength of the colour indicates the confidence level (see text above for a definition of the levels).