piControl — pre-industrial control — is a long simulation of the climate as it was before large-scale human influence, with greenhouse gases, aerosols and land use all held fixed at their roughly-1850 levels.

What it does

Nothing is changed once the run starts. The forcings are constant, so the climate simply settles into its own natural rhythm and drifts only very slowly. These runs are long — often a thousand model years or more — precisely because we want to see that natural, unforced variability play out over centuries.

Why we care

piControl is the reference point for almost everything else on this dashboard:

• Other experiments (like historical or abrupt-4xCO2) branch off from it, so their results are read as a departure from this quiet baseline.
• It tells us how much a climate can wobble on its own, which is how we judge whether a change in another run is a real signal or just noise.
• A stable piControl with little drift is a basic sign the model is behaving.

It is one of the core DECK experiments that every CMIP model runs, which is what lets results be compared across models and across CMIP generations.