Assessing Earth’s Skin Temperature Trends: Consistent Signals from IASI, MODIS, CCI and ERA5

Abstract. Earth’s skin temperature (Tskin), i.e. land and sea surface temperature (LST and SST), directly reflects surface–atmosphere energy exchanges and is an Essential Climate Variable (ECV). Yet it remains less exploited than near-surface air temperature in climate monitoring. Here, we intercompare and assess the capability of several infrared sounders and Tskin products to monitor climate variability during morning and evening overpasses from a multi-sensor perspective over 2008–2022. Two Infrared Atmospheric Sounding Interferometer (IASI) satellite products are analysed: the EUMETSAT all-sky Climate Data Record (IASI-CDR) (all-sky) and a newly developed clear-sky neural-network product (IASI-NN). These IASI products are compared with the Moderate Resolution Imaging Spectroradiometer MODIS Terra Land Surface Temperature (LST) (v6.1), ESA LST CCI (v3.00), and ERA5 skin temperature.

Over land, daytime global means agree within ~2 K across datasets, but LST CCI is consistently higher, and deseasonalised anomalies are highly consistent, except for LST CCI, which exhibits sensor-transition discontinuities. At night, MODIS shows a prevalent cold bias relative to all other products. Over the ocean, inter-dataset biases between IASI and ERA5 generally remain below 1 K. Trend analyses reveal robust warming in Tskin since 2008 across the different datasets, while significant regional cooling is observed over India (daytime) and parts of central/eastern Africa, and in in the southeastern Pacific associated with the Humboldt upwelling system.