Assessing Earth's skin temperature trends: consistent signals from IASI, MODIS, ESA CCI and ERA5

Abstract. Earth's skin temperature (Tskin), i.e. land, ocean/sea, and ice surface temperatures (LST, SST, and IST), 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 instruments and Tskin products to monitor climate variability during morning and evening overpasses from a multi-sensor and reanalysis perspective over 2008–2022. Two Infrared Atmospheric Sounding Interferometer (IASI) satellite products are analysed: the EUMETSAT all-sky Climate Data Record (IASI-CDR) 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), ESA CCI/C3S SST and IST product, and ERA5 skin temperature. Over land, daytime global means agree within ∼ 2 K across datasets, but ESA 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 and RMSE between IASI, ERA5 and ESA CCI/C3S SST and IST globally remain below 1 K. Trend analyses reveal robust warming in Tskin since 2008 across the different datasets over land, while significant regional cooling is observed over India (daytime) and parts of central/eastern Africa, and in the southeastern Pacific associated with the Humboldt upwelling system.