Interpreting differential temperature trends at the surface and in the lower troposphere

Estimated global-scale temperature trends at Earth's surface (as recorded b y thermometers) and in the Lower troposphere (as monitored by satellites) d iverge by up to 0.14 degrees C per decade over the period 1979 to 1998. Acc ounting for differences in the spatial coverage of satellite and surface me asurements reduces this differential, but still Leaves a statistically sign ificant residual of roughly 0.1 degrees C per decade. Natural internal clim ate variability alone, as simulated in three state-of-the-art coupled atmos phere-ocean models, cannot completely explain this residual trend differenc e. A model forced by a combination of anthropogenic factors and volcanic ae rosols yields surface-troposphere temperature trend differences closest to those observed.