Transient simulations of the global fully coupled climate model COSMOS under realistic varying orbital and greenhouse gas forcings are systematically compared to diatom oxygen isotope (δ18O_diatom ) records from Russian lakes with focus on Eurasian Holocene climate trends. The measured δ18O_diatom decrease and other temperature proxies are interpreted as large‐scale cooling throughout the Holocene while the model simulations are biased too warm, likely through missing radiative forcings. This large‐scale warm bias also dictates the modeled δ18O_precipitation. Hence, at locations where the signs of model and proxy temperature/precipitation trends agree, measured δ18O_diatom and modeled δ18O_precipitation trends show notable accordance. An increased temporal variability of modeled δ18O_precipitation is linked to persistent atmospheric circulation patterns. Applying the transient forcings in an accelerated way (every 10th year only) yields a similar, yet weaker or delayed model response, especially in the ocean.