A new global land-ocean merged surface temperature dataset since the 1850s: the CMA-GMST dataset

A new global land-ocean merged surface temperature dataset, China Meteorological Administration global merged surface temperature (CMA-GMST), is developed. It is constructed from the monthly China Meteorological Administration global reconstructed land surface temperature (CMA-GLST) and sea surface temperature (CMA-SST) analyses that benefit from the improved in-situ observation coverage. Besides, the Arctic ice covered area is also reconstructed based on air temperatures and merged into CMA-GMST. This dataset provides a spatial complete and homogeneous surface temperature anomaly field in 2°×2° resolution for each month since 1850, and covers the majority of the earth’s surface: reaches 90% in the middle 1950s and exceeds 99% from the late 1970s. Assessments show that the observed global and regional (terrestrial, oceanic and hemispheric) trends of the annual average anomalies from CMA-GMST agree well with the ranges of trends computed from other published surface temperature analyses. The trends over the different latitudinal zones are also broadly in line with other published surface temperature analyses, while there are some differences in regions with limited observations among the datasets, such as the region of 90S–60ºS. Besides, evaluations by CMA-GMST show that the year 2023 was the warmest year on record and each month from July 2023 to December 2023 ranked as the globe's hottest month in recorded history, which agree well with the evaluations from other published surface temperature analyses.