  Climate models are thought to solve boundary value problems unlike numerical
weather prediction, which is an initial value problem. However, climate
internal variability (CIV) is thought to be relatively important at near-term
(0-30 year) prediction horizons, especially at higher resolutions. The recent
availability of significant numbers of multi-model (MME) and multi-initial
condition (MICE) ensembles allows for the first time a direct sensitivity
analysis of CIV versus model response variability (MRV). Understanding the
relative agreement and variability of MME and MICE ensembles for multiple
regions, resolutions, and projection horizons is critical for focusing model
improvements, diagnostics, and prognosis, as well as impacts, adaptation, and
vulnerability studies. Here we find that CIV (MICE agreement) is lower (higher)
than MRV (MME agreement) across all spatial resolutions and projection time
horizons for both temperature and precipitation. However, CIV dominates MRV
over higher latitudes generally and in specific regions. Furthermore, CIV is
considerably larger than MRV for precipitation compared to temperature across
all horizontal and projection scales and seasons. Precipitation exhibits larger
uncertainties, sharper decay of MICE agreement compared to MME, and relatively
greater dominance of CIV over MRV at higher latitudes. The findings are crucial
for climate predictability and adaptation strategies at stakeholder-relevant
scales.
