2026-02-16 update

Further to the update circulated on 12 February, there has been an iteration on the recommendation for piControl as follows:

Recommendation for pre-industrial control

The piControl forcing should come from files with the source ID FZJ-CMIP-ozone-1-2, (there are no specific piControl files available in the FZJ-CMIP-ozone-2-0 data). Note that this guidance differs from the email communication sent by the CMIP IPO on 12 February 2026.

For pre-industrial control, there are two options. The first is the monthly climatology file (frequency value of monC). This dataset averages over a longer simulation, essentially removing variability like the QBO. If you wish to use this forcing for your piControl, simply apply it on repeat.

The second is a transient file which has a time range equal to 182901-184912 in the filename. This file is found in the same directory as the historical forcing so please be careful to only use it for piControl and do not include it in historical forcing. This transient piControl forcing includes the QBO signal but uses average solar forcing and repeating 1850 emissions. If you wish to use this forcing for your piControl, simply apply it on repeat.

For full details on the ozone dataset please see Ozone concentrations - input4MIPs Controlled Vocabularies (CVs)