"Century simulations" refers to computer models or simulations that mimic conditions over a period of 100 years. This phrase is often used in fields such as climate science to study long-term trends and predict future changes. Full definition
Analysis of a twentieth century simulation indicates that ten year periods with zero or negative temperature trends are likely (p > 0.05). (pnas.org)
In the 20th century simulations, however, the ocean overwhelmingly exhibits warming in these deeper layers. (skepticalscience.com)
This can be compared with the net forcings that we currently use in our 20th Century simulations based on the best estimates and observations of what actually happened (through to 2003). (realclimate.org)