Augures

Decadal Forecasts

Decadal forecasts aim to estimate how likely it is for a particular geographical region to experience warmer or colder and wetter or drier than average conditions in the coming years. This is crucial information for weather-sensitive sectors like agriculture.

Despite the chaos in the atmosphere, getting such a glimpse into the future is possible due to the presence of slowly evolving fields, such as sea surface temperature, soil moisture, and snow cover, and phenomena such as El Niño-Southern Oscillation in the Earth system.

Given the pronounced and unavoidable uncertainty in predicting the long-term evolution of the Earth system, decadal forecasts have to be probabilistic. To that end, probabilistic estimates about the average weather conditions in the years ahead are derived by running one or, ideally, several different models multiple times to produce an ensemble of equiprobable outcomes.

Despite the ever-growing availability and accessibility of decadal forecasts, it has to be emphasised that these long-term forecasts are characterised by significant uncertainty and aim to estimate the tendency in the yearly evolution of average weather conditions. Daily and local weather conditions may differ significantly from the seasonal and annual average conditions in a broader region. Therefore, a decadal forecast system is neither built nor able to foresee extreme weather episodes, like heat waves and tropical cyclones, years in advance.