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2026-06-19 update#

Subject: Notice of issue with CEDS CMIP7 aviation emissions data for 2023, and consequently, all scenario data (which uses 2023-historical seasonality for anthropogenic emissions).

Dear Modelling centres (science and forcings contacts),

We would like to make you aware of an error that has been identified in the seasonality of aircraft emissions in the scenario forcing. The issue stems from an error in the 2023 seasonality, which was subsequently used for the scenario emissions. Please note this issue does not affect the CMIP7 historical simulations (which end in 2021).

Issue detail#

An input processing error in the Carbon Monitor data used to generate the monthly air seasonality has caused some January-June 2023 aviation values to be inadvertently counted twice. This has resulted in:

  1. Artificially inflated aviation emissions during the first half of 2023
  2. Suppressed emissions during the second half of 2023
  3. An unrealistic seasonal profile compared with surrounding years

Impacts and proposed action#

The CMIP Forcings TT co-leads have completed some further investigation to determine the impact of this issue in the seasonality on ozone simulation for 2023. They, together with the ozone dataset provider, have concluded that the impact is likely small, can be treated as a forcing uncertainty, and is not significant enough to warrant a rerun of ozone forcing simulations.

They encourage ESMs (with full chemistry) that have not yet started their ScenarioMIP simulations to use the corrected emissions, once available. Those that have already completed the simulations can decide whether to rerun depending on their resources and any other demands.

When will the corrected emissions data be available?#

Corrected emissions for all scenarios will be available from the ESGF (via the input4MIPs portal by Friday 26 June. If you have any questions, please raise an issue or start a discussion at https://github.com/PCMDI/input4MIPs_CVs/discussions

Best wishes,

CMIP IPO on behalf of CMIP Forcings Task Team and CMIP Panel Co-chairs