Locked in warming is heat accumulation that will occur inevitably based on current carbon dioxide concentration. The MEER organization calculates that the existing greenhouse gases cause an energy imbalance of about 2 watts per square meter on Earth’s surface - a somewhat instantaneous rate, that depends on various Earth system factors like albedo (reflectivity), infrared absorption efficiency in the atmosphere, and surface temperature. If none of these factors change significantly over the coming decades, this rate of heating will continue.
Will carbon dioxide concentration remain constant? Probably not. According to Explainer: Will global warming ‘stop’ as soon as net-zero emissions are reached? - Carbon Brief, the prospect of constant CO2 could arise in an almost net-zero world, where residual emissions are balanced by removal processes. But with net-zero emission and CDR combined, CO2 concentration can decrease.
how is this relevant to CDR? Can CDR affect albedo (possibly, positively or negatively) or infrared absorption? (probably yes if CO2 is decreased). Can CDR affect CO2 concentration in the atmosphere? Certainly. If we can reduce the CO2 concentration we can change the energy balance.
what is the consequence of 2W/m2? simple calculations suggest it is not significant, even if the heating is confined to upper ocean - this heating rate seems wrong. However, MEER calculates a locked in warming of 1C regardless of net-zero emissions. The locked-in warming concept deserves further elaboration here from additional sources, because the existence of locked-in warming is also a potential argument in favor of CDR, because the MEER concept might compete for resources with CDR, and because the MEER concept might be a complementary response - integrable with some kinds of CDR efforts.