Joint probability plots

Also known as a contour plots, these are graphs that show the relative probability of projected changes in one variable consistent with projected changes in another. They can be produced via the UKCP09 User Interface using the sampled model output. See the rules for producing joint probabilities in this FAQ. 

The contours on the diagrams represent a probability that has been multiplied by 1000. For instance if a relative probability of "2" is indicated on the contour line this relates to a probability of 0.002 that there will be a simultaneous change in a certain amount in variable X and a certain amount in variably Y.

They can be produced for the Climate change projections and the Marine & coastal projections to show:

• Projected climate change or projected future climate
• For two variables
• For one location
• For one time period
• For one temporal average
• For one emissions scenarios
• Probability contours to indicate the relative probability of different joint occurences. 

Joint probability plots can exported from the User Interface as images in various file formats (PDF, PS, PNG and JPG). The underlying values can be exported as a comma-separated variable (*.csv) and CF-netCDF format file. CSV files can be opened as a spreadsheet. 

• What should I use them for?

• To illustrate the joint probability of changes in two variables
• To suggest what projected combinations of changes can effectively be ruled out

More details…

• What to be aware of

• Joint probability plots should not be used for exploring the joint probability associated with climate change being greater than or less than certain amounts
• They should not be used for detailed analysis of the joint probability of changes in more than two variables

More details…