Create 2026-03-20.md

Author: eleanororourke

docs/forcings-email-archive/2026-03-20.md

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+# 2026-03-20 update
+
+There is an update to the nitrogen deposition data (new data is published under source ID FZJ-CMIP-nitrogen-2-0). However, if you already have simulations that use the previous version (source ID FZJ-CMIP-nitrogen-1-2`), you do not need to re-run. Further details below and at https://input4mips-cvs.readthedocs.io/en/latest/dataset-overviews/nitrogen-deposition/
+
+As a result of an issue being found (#425), a new version of the nitrogen deposition forcing has been released.
+* Modelling centres who have already run their piControl and/or historical simulations do not need to re-run.
+* Modelling centres who have not yet started their piControl and/or historical simulations should use the FZJ-CMIP-nitrogen-2-0 data.
+For further details about the error and recommended action, please see the nitrogen deposition dataset page https://input4mips-cvs.readthedocs.io/en/latest/dataset-overviews/nitrogen-deposition/.
+
+If any modelling centres run piControl and/or historical simulations with both the FZJ-CMIP-nitrogen-2-0 and FZJ-CMIP-nitrogen-1-2 forcing,
+these simulations would be of interest to the Forcings Task Team. ([#427](https://github.com/PCMDI/input4MIPs_CVs/pull/427))