Simulated Transient Climate Response to Precessional Forcing: with and without Orbital Acceleration

Orbital acceleration is widely used in transient orbital simulations with atmosphere–ocean general circulation models (AOGCMs) to make the investigation of long-term climate variability computationally feasible. However, the effects of different acceleration rates have not been systematically evaluated and may introduce substantial biases. Here, we compare simulations with acceleration rates of up to 100× against a non-accelerated control over a full 22-kyr precession cycle, with a focus on surface temperature and precipitation. The results show that the acceptable acceleration rate is strongly region dependent: acceleration rates of up to 100× generally preserve the full-precession response over much of the land, particularly in monsoon regions, whereas responses in oceanic regions such as the North Atlantic subpolar gyre show greater sensitivity to acceleration. In addition, orbital acceleration does not reliably resolve half-precession, quarter-precession, or higher-frequency variability.