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Copernicus ERA5 Reanalysis

Global hourly climate reanalysis for building location-specific weather-history tools from a tightly bounded ERA5 extract.

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At a glance

Difficulty
Advanced — expect specialized tools or domain knowledge
Size
Large · ≤50 GB
Formats
NetCDF, GRIB
Access
API or Download
API key
Required
Provider
Copernicus Climate Change Service
Updates
Daily
Data terms
Licence to use Copernicus Products

From source to product signal

Test a product idea in four steps

ERA5 is a global reanalysis on the Climate Data Store. Start with one variable, one hour, and a few-kilometer bounding box. Reanalysis blends observations and a model, so it is not a station measurement, and CDS jobs are queued rather than instant.

1

Check the setup

  • Python 3.10 or newer
  • A notebook environment such as Jupyter or Google Colab
  • A CDS account, accepted ERA5 licence, and CDSAPI_KEY environment variable
2

Access the data

  1. 1.Register at the Climate Data Store and accept the ERA5 dataset licence on the download form.
  2. 2.Save your personal access token in CDSAPI_KEY.
  3. 3.Retrieve 2-metre temperature for one hour over a tiny bounding box as NetCDF.
Open official source
3

Run the Python example

Install the packages, then run the notebook cell.

python -m pip install cdsapi xarray netCDF4

import os
import cdsapi
import xarray as xr

client = cdsapi.Client(
    url="https://cds.climate.copernicus.eu/api",
    key=os.environ["CDSAPI_KEY"],
)
client.retrieve(
    "reanalysis-era5-single-levels",
    {
        "product_type": ["reanalysis"],
        "variable": ["2m_temperature"],
        "year": ["2024"],
        "month": ["07"],
        "day": ["15"],
        "time": ["12:00"],
        "area": [40.8, -74.05, 40.7, -73.95],
        "data_format": "netcdf",
        "download_format": "unarchived",
    },
    "era5_nyc_sample.nc",
)
sample = xr.open_dataset("era5_nyc_sample.nc")
print(sample)
4

Test a useful signal

Reconstruct one hour of 2-metre temperature

Test whether a tiny ERA5 extract can power a site-history prototype.

  1. 01Confirm the NetCDF contains 2-metre temperature for the requested hour and bounding box.
  2. 02Convert temperature from kelvin to Celsius and record the grid-cell center used.
  3. 03Explain that ERA5 is a reanalysis grid, not a weather-station observation, and that queued CDS jobs can delay retrieval.

Dataset details

Copernicus Climate Change Service is an intergovernmental source. Last verified 2026-08-18. Temporal coverage: 1940-present.

Theme

Environment & Hazards

Domains

ClimateWeatherEnvironmental Science

Data types

Gridded DataTime Series

Tasks

Climate AnalysisHistorical Weather ReconstructionSite Screening

Geography

Global

Formats

NetCDFGRIB

Provider

Copernicus Climate Change Service

Data terms

Licence to use Copernicus Products