The Earth Institute’s International Research Institute for Climate and Society makes probabilistic forecasts for rainfall and temperature for the next six months. How does it do this?
This spring, IRI implemented a new methodology for seasonal temperature and precipitation forecasts. We asked Simon Mason, Andrew Robertson and Tony Barnston, senior climate scientists who lead the development and tailoring of IRI’s forecasts, to answer some fundamental questions about the new forecast.
The December 2011 precipitation forecast issued by the International Research Institute for Climate and Society called for a 75 percent chance of above normal precipitation over parts of the Philippines between January and March. As the months played out, storms brought roughly eight inches more rain than usual for the period. That’s about 85 percent more than usual. Does this mean the forecast was right? What if the storms never materialized and the region received eight inches of rain less than normal? Would the forecast then have been wrong?