Please note: CAMS global forecast test data is available from 05-2025 onwards but only data from 17 Jul 2025 has GRIB metadata fully correct.
MARS archive
If you have access and you can retrieve data from the MARS catalogue, please use the following keywords for the CAMS global forecast test data:
class=mc expver=0080
Here the link to directly access the data in the MARS catalogue (please remember that ecCodes version 2.44.0 or later is required to handle the full range of parameters of current CAMS data).
Atmosphere Data Store (ADS)
If you cannot retrieve data from the MARS catalogue, you can retrieve the data from the cams-global-atmospheric-composition-forecasts-test dataset using the API.
Read documentation of the API.
If you haven't done it yet, you will need to create an ECMWF account and accept the terms of use.
The test data is only accessible through the ADS API service, and it is not possible to use the interactive web interface to download it.
You can use existing requests for the CAMS global atmospheric composition dataset by replacing the dataset name with "cams-global-atmospheric-composition-forecasts-test".
Data are available from from 05-2025 onwards but only data from 17 Jul 2025 has GRIB metadata fully correct.
API Example
Select 10 dates and day 1 forecast (from hour 0 to 24):
import cdsapi
dataset = "cams-global-atmospheric-composition-forecasts-test"
request = {
"variable": [
"anthropogenic_secondary_organic_aerosol_mass_mixing_ratio",
"formaldehyde",
"temperature"
], # See other variables at:https://ads.atmosphere.copernicus.eu/datasets/cams-global-atmospheric-composition-forecasts?tab=download
"model_level": ["137"], # Lowest model level
"date": ["2026-02-17/2026-02-27"],
"time": ["00:00"],
"type": ["forecast"],
"leadtime_hour": [h for h in range(0,25,3)],
"data_format": "netcdf_zip"
}
client = cdsapi.Client()
client.retrieve(dataset, request).download()
ECMWF data portal (aux.ecmwf.int; SFTP/FTP/HTTPS data access)
The test dataset is available through ECMWF data portal (aux.ecmwf.int; SFTP/FTP/HTTPS data access) in these directories:
/DATA/CAMS_GLOBAL_TEST /DATA/CAMS_GLOBAL_ADDITIONAL_TEST /DATA/CAMS_EUROPE_BC_TEST
You can use your normal FTP account to access the data. Details about filenames convention or list of available parameters can be found at CAMS Knowledge Base.
ECMWF dissemination
Users with access to ECPDS and the Products Requirements Editor (PREd) can login to the test systems here:
- Test ECPDS: https://xdiss-monitor.ecmwf.int/
- Test PREd (TPREd): https://products.ecmwf.int/esuite/requirements/
Users can then trigger the transmission of test products in the usual manner. To receive the test products, users have to have their firewall open to the relevant ECPDS Data Movers:
INTERNET:
- 136.156.192.0/26
- 136.156.193.0/26
RMDCN:
- 136.156.196.0/26
- 136.156.197.0/26
The CAMS Cycle 50r1 test products are available as version number 80 (file names including '*80' as expver) and are intended to be generated shortly behind near real-time.
If you wish to receive 50r1 test data automatically (regularly) you don't have access to the ECPDS system or (T)PREd or should require any assistance with CAMS Cycle 50r1 test dissemination products, please contact ECMWF Support via the Support Portal .
Users are strongly advised to check that their software applications and data processing chain can handle the test data.
If everything else fails ...
... you can always contact us on ECMWF Support Portal creating a ticket "Request for CAMS global test dataset" as a subject and specify:
- which parameters and levels
- which time period
- forecast step / time frequency
- which geographical area
- which data format you require
