Forcing and feedback mechanisms of rainfall on centennial to millennial timescales

Reconstructions of past changes in the hydrological cycle suggest that forcing and feedback mechanismsat centennial to millennial timescales result in a nonuniform spatiotemporal response. Modelling effortsare critical to understand the competing impacts of different forcings on rainfall and support a substantialregional character in response to those forcing factors. However, simulating past rainfall changes remainsa difficult task and there exists a large model spread in regional rainfall amount, particularly in the tropics,with some model results diverging from reconstructions. On the other hand, debate exists on theappropriate interpretation of rainfall proxy records and whether and how they reflect the amount ofrainfall. Quantifying past rainfall changes, as opposed to the available qualitative rainfall proxy records,allows for a more reliable rainfall reconstruction and a more accurate comparison to model simulations. Tothis end, calibration of site-specific rainfall proxies to local rainfall amount on multidecadal timescale hasshown a great potential and will help, together with ocean temperature proxy data, to elucidate regionaland global rainfall dynamics and trends on longer timescales.