What was done
The authors used TOMS (Total Ozone Mapping Spectrometer) 380-nm reflectivity data to determine changes in radiation reflected back to space over the period 1979 to 1992.

What was learned
In the words of the authors, "when the 11.3-year solar-cycle and ENSO effects are removed from the time series, the zonally averaged annual linear-fit trends show that there have been increases in reflectivity (cloudiness) poleward of 40°N and 30°S, with some smaller but significant changes occurring in the equatorial and lower middle latitudes."  The overall long-term effect, they say, is for an increase in radiation reflected back to space of 2.8 Wm^-2 per decade (standard deviation of ± 1.4 Wm^-2 per decade).

What it means
Although a precise estimate of the cooling effect of this phenomenon cannot be given, the authors say "the uncertainty is small enough to know that there is a likely cooling effect from additional radiation reflected to space."  They further note that this cooling effect is provided "by changes in the amount of snow/ice, cloudiness, and aerosols."  Hence, it is clear that some of earth's best negative feedback effects are indeed working - and quite successfully - to maintain planetary surface air temperatures within a range that is suitable for the continued existence, and even robustness, of life.