As our planet heats up, tracking changes in forest aboveground biomass density at large scales is an increasingly pressing concern and one addressed primarily using space-based remote sensing. For example, NASA launched the Global Ecosystem Dynamics Investigation (GEDI) vegetation canopy lidar in 2018 and the NASA-ISRO SAR (NISAR) and ESA BIOMASS radar missions are slated to launch in 2024. However, the record from radar and lidar missions is geographically and temporally limited. Here, forest biomass estimates obtained by NASA’s Multiangle Imaging Spectro-Radiometer (MISR) using measurements of reflected sunlight in the red wavelengths and from the GEDI spaceborne lidar are compared with those from NASA Carbon Monitoring System (CMS) airborne lidar surveys for sites in California. MISR and GEDI gridded 1 km AGB estimates are highly compatible with those from the CMS surveys. Using the data from all CMS sites, 70% of the variance is explained; and for the Sonoma Co. “improved” CMS data set, about 88% of the variance is explained, with good precision. This means that MISR performs almost as well as GEDI at 1 km, but the annual 250 m MISR map series extends across the southwestern U.S. and back to the year 2000.