However, a relationship between warming temperatures and precipitation extremes provides an alternate means for adjusting historical IDF curves. This ‘temperature scaling’ relationship is being increasingly used to estimate future Canadian rainfall extremes. It is described in CSA PLUS 4013 and is being used to develop future rainfall estimates for the National Building Code of Canada and Canadian Highway Bridge Design Code.
Temperature scaling provides a simple way to update IDF curves for climate change. However, careful consideration of uncertainties in estimates of future extreme rainfall is still required. Scaling factors may vary between locations and rainfall event types. Local temperature change projections depend on future emissions, climate model choices, and natural variability. And the historical IDF curves that underlie any future IDF curves estimates may themselves be less than ideal estimates of past rainfall extremes.