The phrase "equilibrium sensitivity" refers to how sensitive something is to being balanced or in a state of stability. It represents how easily a situation or system can be thrown off balance or disturbed. Full definition
Researchers need to know the transient response and equilibrium sensitivity of climate forcings. (giss.nasa.gov)
The challenge with this «instrumental» method of estimating equilibrium sensitivity is that it's based on transient instrumental measurements. (skepticalscience.com)
It is possible that effective climate sensitivity increases over time (ignoring, as for equilibrium sensitivity, ice sheet and other slow feedbacks), but there is currently no model - independent reason to think that it does so. (judithcurry.com)