GHCNm
NOAA GHCNm overview
GHCNm is the long-horizon climate archive on Climate Explorer. It is built for questions that monthly data answers well: multi-decade warming, precipitation shifts, homogenized station histories, and century-scale regional comparisons.
Curated by NOAA/NCEI, this dataset is a cornerstone for monitoring global climate change and analyzing long-term trends. The current v4 release combines monthly temperature and precipitation statistics, applies automated homogenization, and continues to receive updates from active stations.
Looking for data for your country?
This dataset contains meteorological records for every country in the world. If you do not see a dedicated dashboard for your specific region elsewhere on Climate Explorer, you will find the data here.
Why this dataset matters
- Provides a globally consistent baseline for comparing climate signals between continents, regions, or single stations.
- Offers homogenized series that correct for instrument changes, relocations, and reporting gaps, which is crucial for long-term trend detection.
Coverage and refresh cadence
GHCNm v4 currently spans 1750 to present (station dependent). New station files are ingested monthly, with NOAA applying additional quality flags before publication. Climate Explorer ingests the public release within a few days to keep the explorer synchronized with the upstream reference archive.
Use the interactive explorer
Use the panel controls to discover individual stations, focus on a variable, narrow the year range, and export monthly summaries for further analysis.
About this Data
The GHCNm (Global Historical Climatology Network Monthly) is the world’s primary baseline dataset for long-term climate analysis. Maintained by NOAA NCEI (National Centers for Environmental Information), this massive archive aggregates quality-controlled observations from over 20 global data sources, including the WMO Information System and various national meteorological archives.
Through Climate Explorer, you gain streamlined access to this global network without needing to parse complex text files. The data facilitates:
- Global Climate Monitoring: Tracking temperature trends and precipitation patterns across continents.
- Long-term Trend Analysis: Investigating climate change signals, warming trends, and decadal variability.
- Regional Climate Assessment: Evaluating historical weather patterns with worldwide ground-truth data.
Unique Value: Clean Long-Term Signals
Most climate datasets are fragmented by national borders. GHCNm unifies them. Whether you are analyzing monsoon trends in India, winter storms in Canada, or heat stress in Australia, this explorer provides a consistent interface for every country in the world.
The dataset features monthly resolution, which is critical for capturing long-term climate trends and historical variability that daily data might obscure or be too noisy for.
How to use this tool
- Global Navigation: The map starts with a global view. Click on any blue dot to select a station.
- Filter by Country: Use the sidebar dropdown to instantly zoom into a specific nation’s network (e.g., “United Kingdom”, “Brazil”, “South Africa”).
- Adjust Time Window: The dashboard loads the full available history (1750 to present). Use the Year Range slider to focus on specific decades or centuries.
- Visualize & Export:
- Plots: Inspect the monthly time series charts with linear trend lines to visualize long-term warming or cooling signals, along with the computed slope (°C/year) and mean.
- Data: Switch to table view to download the raw CSV data for your research.
How to Interpret GHCNm Records
GHCNm is best understood as a long-term monthly climate archive. It is designed for questions about multi-year and multi-decadal change: warming trends, rainfall shifts, baseline differences between regions, and the long historical behavior of individual stations.
When interpreting the explorer, keep these points in mind:
- Monthly Data Emphasizes Climate Signals: By aggregating conditions over each month, the dataset suppresses day-to-day noise and makes longer-term patterns easier to interpret.
- Homogenization Improves Trend Analysis: The monthly series are particularly valuable for detecting broad climate changes because the archive applies quality-control and homogenization procedures to reduce artificial shifts.
- Station Histories Differ: Some stations have very long records, while others begin later or include interruptions. Comparisons are strongest when the overlap period is clear.
- Monthly Data Is Not Event Data: This archive is excellent for trends and seasonal structure, but not for analyzing the precise timing of storms, heat spikes, or short-duration extremes.
- Regional Context Still Matters: A monthly average or total reflects the local environment of a station, so coastal, mountainous, urban, and inland locations can still differ sharply.
What This Explorer Is Best For
The GHCNm explorer is particularly strong for analyzing long-term climate change, comparing monthly station histories across countries, and identifying broad warming or precipitation patterns over decades. It is less suitable for near-real-time monitoring or sub-daily weather analysis, where tools such as the EuroMeteo Explorer, GHCNh Explorer, and national high-resolution explorers like DWD, Météo-France, JMA, or IMGW are better fits.
Need more help? View the full About page for contact information.
Data source and code
- Dataset: We have used the GHCNm Version 4 dataset available at https://www.ncei.noaa.gov/data/global-historical-climatology-network-monthly/v4/temperature/archive/ (Temperature) and https://www.ncei.noaa.gov/data/ghcnm/v4/precipitation/archive/ (Precipitation).
- Data source flags: Definitions are documented at https://www.ncei.noaa.gov/data/ghcnm/v4/temperature/doc/ghcnm-flags.
- For any inquiries or feature requests, please use the contact form available in the About section.
Source material and citation
- Official NOAA documentation for the dataset is available through the NCEI GHCNm landing page.
- When referencing results, cite NOAA/NCEI as the data originator and include the Climate Explorer URL so readers can reproduce the visualization workflow.
- For methodology details, consult the v4 technical note and quality-control addenda included on the official download page.
Frequently Asked Questions
What is the GHCNm dataset?
The Global Historical Climatology Network Monthly (GHCNm) is a comprehensive database of historical monthly temperature, precipitation, and climate summaries from thousands of land stations worldwide, maintained by NOAA.
Why use monthly data instead of daily or hourly?
Monthly data strips away the noise of day-to-day weather fluctuations, making it the ideal resolution for identifying long-term climate trends, detecting global warming signals, and analyzing decadal variability over the course of centuries.
Are the historical data records homogenized?
Yes. The GHCNm version 4 dataset applies automated homogenization algorithms to the temperature data. This process identifies and corrects artificial shifts in the data caused by station relocations, changes in instrumentation, or urban heat island effects, ensuring that the Long-term trends you see are genuine climate signals.
How often is the GHCNm data updated?
NOAA NCEI publishes updated public releases on a regular basis. Climate Explorer synchronizes with those upstream releases so you are working from the most current archive available there.
How do I analyze long-term climate trends?
Click on any station on the map to generate monthly time series plots. Each plot displays the raw monthly values over the station’s entire record, overlaid with a linear trend line (in gray). Below each chart, the dashboard shows the slope (rate of change per year, e.g., +0.02 °C/year) and the long-term mean. Use the Year Range slider to focus on specific decades or centuries.
Browse featured GHCNm pages
Quick links to curated monthly climate pages selected from the global NOAA GHCNm explorer.