Uncertainty in Projected Precipitation Change Exposed: A Study on Aggregation to the River-Basin Scale

Strategic Insights -

Research conducted by the Royal Netherlands Meteorological Institute and funded by the European Union's Horizon 2020 program has shed light on the uncertainty in projected precipitation change. The study aimed to provide guidance on processing uncertainty information depending on application-specific needs. According to the research, model projections of changes in precipitation express large uncertainties, partly due to climate noise from internal variability dominating the greenhouse gas forced signal.

Key Takeaways:

  • The study found that the forced climate signal is moderately dependent on spatial aggregation, but uncertainties and signal-to-noise ratios strongly depend on the aggregation method.
  • Computing uncertainties at the grid scale and averaging those to larger areas leads to large uncertainty estimates and low signal-to-noise ratios.
  • Computing changes at the grid scale, spatially averaging those per ensemble member, and computing the uncertainty in these spatial averages results in much smaller uncertainty estimates, up to a factor of 2 for 1-day precipitation maxima in summer.
  • Spatial aggregation of precipitation itself and computing uncertainties in basin-scale precipitation changes yields smaller uncertainties, up to a factor of 1.5 for 1-day summer maxima.
  • The research has significant implications for stakeholders with aggregated uncertainty perspectives, such as insurance companies.

Statistics:

  • The uncertainty in projected precipitation change is up to a factor of 2 for 1-day precipitation maxima in summer.
  • Spatial aggregation of precipitation yields smaller uncertainties, up to a factor of 1.5 for 1-day summer maxima.
  • The study involved a high-resolution initial-condition regional climate model ensemble.
  • The research was funded by Horizon 2020, European Union (EU).
  • The study has been peer-reviewed.

Sources:

  • Uncertainty In Projected Precipitation Change and Its Dependency On Aggregation To the River-basin Scale. Journal of Geophysical Research-atmospheres, 2025; 130(15)
  • Royal Netherlands Meteorological Institute, De Bilt, Netherlands
  • Geert Lenderink, Erik van Meijgaard, Hylke de Vries, and Bart J. J. M. van den Hurk
  • Emma E. Aalbers, Royal Netherlands Meteorological Institute Knmi, De Bilt, Netherlands.