Leveraging data archived at NCEI, NOAA has released a new version of the monthly Global Historical Climatology Network dataset. Commonly known as GHCN–Monthly (GHCNm), the dataset is an internationally recognized public source for the study of observed changes and variability in land surface temperature. Version 4 serves as an enhanced tool for studying and monitoring Earth’s climate.

GHCNm, a large set of monthly mean, maximum, and minimum temperature data over global land areas, has been enhanced to incorporate data from thousands of additional reporting stations. In the process, GHCNm now aligns more closely with its daily counterpart, GHCN–Daily (GHCNd), which is consistently a highly utilized dataset developed by NCEI.

The initial release of GHCNm version 4 contains monthly mean temperatures; maximum/minimum temperature and precipitation data will be added at a later date.

New Version Incorporates Station Data Available in GHCN–Daily

The new version of GHCNm makes use of the large number of daily temperature summaries from weather stations around the world available in GHCNd.

A paper in the Journal of Climate about GHCNm v4 describes the changes in detail. Besides utilizing the temperature data available in GHCNd, GHCNm version 4:

• Makes use of additional historic temperature values collected under the auspices of the International Surface Temperature Initiative (ISTI)

• Expands both the number and the global coverage of temperature stations throughout the period of record and increases the number of stations that are regularly updated

• Provides more complete uncertainties associated with calculating station and global temperature averages

The journal article, coauthored by scientists at NCEI and the Cooperative Institute for Climate and Satellites–North Carolina (CICS-NC), provides details of each of the processing steps used to develop version 4. For example, researchers must consider how temperature data are collected, if methods or station locations change over time, or if there are incomplete data in certain regions.

History and Uses of GHCN–Monthly

GHCNm was first released in 1992 as the most comprehensive set of land station data at the time. It provided a historical perspective on climate change and variability. A second version, released in 1997, increased the number of stations and the length of the data record and introduced regular updates for climate monitoring. The third release, in May 2011, incorporated improvements in quality control and advances in techniques for data analysis.

GHCNm is used operationally for climate monitoring activities, such as the Global Climate Report, authored and released by NCEI. Maps, graphs, and models are also developed using the dataset. Atmospheric scientists and industry-specific researchers in sectors such as energy, defense, insurance, and agriculture constitute major users of GHCNm.