Different Flavors of Normals: Accounting for ENSO and Climate Change

Climate normals have traditionally been calculated every decade or so as the average values over a long period of time, often 30 years. Such an approach assumes a stationary climate, so several so-called alternative normals have been recently introduced. These typically attempt to account for trends associated with global climate change by using a shorter averaging period, more frequent updates, and/or extrapolating the linear trend. While such approaches account for monotonic climate change, they fail to harness known interannual climate variability such as that associated with the El Niño-Southern Oscillation (ENSO). Similar to climate change, ENSO systematically alters the background state of the climate. These effects and their uncertainties are relatively well established, but they are not reflected in any readily available climate normals datasets. This presentation will highlight initial steps towards producing temperature and precipitation normals for United States that reflect the variability associated with ENSO.