1. Remote Sensing Systems, 438 First Street, Suite 200, Santa Rosa, California 95401, USA

Correspondence to: Frank J. Wentz Correspondence and requests for materials should be addressed to F.J.W. (e-mail: Email: wentz@remss.com).

Observations from Earth-orbiting satellites have been a key component in monitoring climate change for the past two decades. This has become possible with the availability of air temperatures from the Microwave Sounding Unit (MSU)¹ since 1979, sea surface temperatures from the Advanced Very High Resolution Radiometer (AVHRR)² since 1982 and, most recently, measurements of atmospheric water vapour content from the Special Sensor Microwave Imager (SSM/I)³ since 1987. Here we present a detailed comparison of each pair of these three time series, focusing on both interannual and decadal variations in climate. We find a strong association between sea surface temperature, lower-tropospheric air temperature and total column water-vapour content over large oceanic regions on both time scales. This lends observational support to the idea of a constant relative humidity model having a moist adiabatic lapse rate. On the decadal timescale, the combination of data sets shows a consistent warming and moistening trend of the marine atmosphere for 1987–1998.