'Night Marine Air Temperature' in Global Climate in State of the Climate 2022

Air temperature measurements have been made onboard ships for centuries and continue to be collected today thanks to the Voluntary Observing Ship initiative (https://www.ocean-ops.org/reportcard2022/). Gridded datasets of marine air temperature (MAT) are constructed from the individual measurements, and two such datasets that are routinely updated are used in this section: University of Alabama in Huntsville night-time MAT (UAHNMAT; Junod and Christy 2020) and Climate Linked Atlantic Sector Science night MAT (CLASSnmat; Cornes et al. 2020). Since daytime MAT observations are biased warm due to heating from the ship superstructure, only night-time values are currently used in these datasets and, hence, they are referred to as night marine air temperature (NMAT). These NMAT datasets provide comparison against the more widely used sea-surface temperature (SST) datasets. In keeping with this theme, we also include SST statistics from The Met Office Hadley Centre's sea-surface temperature dataset (HadSST4; Kennedy et al. 2019) in this section. Note, however, that the large-scale average values from HadSST4 presented in this section (Fig. 2.5 and Table 2.2) may differ slightly from other estimates from the dataset presented in this report because the data have been masked such that the spatial coverage is the same across the three datasets in order to ensure a fair comparison.