CRUTEM

CRUTEM, short for Climatic Research Unit Temperature, is a dataset of land surface air temperature anomalies compiled by the Climatic Research Unit (CRU) at the University of East Anglia. It provides gridded and station-based representations of global land temperatures and is a core component of the HadCRUT global temperature record.

The dataset relies on thousands of meteorological stations worldwide. After quality control and homogenization to correct for non-climatic changes such as station moves and instrumentation changes, monthly mean temperatures are computed relative to a historical baseline to yield anomalies. These anomalies are then interpolated to a regular grid to produce gridded temperature fields. CRUTEM data are often combined with sea surface temperature datasets to form comprehensive global temperature records.

CRUTEM has evolved through several revisions, including CRUTEM3, CRUTEM4, and CRUTEM5, each expanding station coverage and refining homogenization and interpolation methods. The resulting land temperature anomalies underpin the HadCRUT family of global surface temperature series, widely used in climate research and in assessments of historical global warming.

Limitations and uncertainties reflect the uneven geographical and temporal coverage, especially in earlier decades and remote regions. Methodological challenges include residual non-climatic biases, urbanization effects, and changes in observation practices, all of which are addressed through ongoing quality control and homogenization efforts. The CRUTEM dataset remains a key resource for scientists studying climate variability and change, and for informing public understanding of long-term temperature trends.