What does a joint probability plot show?

The joint probability of changes in two climate variables, in the form of a contour plot.

In detail

A joint probability plot is an easy way of assessing how two variables correspond to each other, such as warmer, wetter winters or hotter, drier summers. The UKCP09 User Interface allows joint probability plots to be produced that show probabilistic projections for two climate variables on the same graph.

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 0.0002 that there will be a simultaneous change in a certain amount in variable x and a certain amount in variably y.

Please see Interpreting joint probability plots for more information.