What was done
The authors analyzed aerosol optical properties retrieved from the satellite-mounted Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and used them in conjunction with a radiative transfer model of earth's atmosphere to calculate the climatic effects of aerosols over the earth's oceans.

What was learned
Over the major global oceans, the authors report that "aerosols reduce the annual-mean net downward solar flux by 5.4 Wm^-2 at the top of the atmosphere, and by 5.9 Wm^-2 at the surface."  During the time of the large Indonesian fires of September-December 1997, however, the radiative impetus for cooling at the top of the atmosphere was more than 10 Wm^-2, while it was more than 25 Wm^-2 at the surface of the sea in the vicinity of Indonesia.

What it means
The magnitude of the radiative warming impetus typically predicted to occur in response to a doubling of the air's CO2 content - which is still a future event (and probably quite distant at that) - is about 4 Wm^-2.  Hence, it can be appreciated that over the majority of the planet's surface, the radiative cooling influence of atmospheric aerosols (many of which are produced by anthropogenic activities) prevails, suggesting a probable net anthropogenic-induced climatic signal that must be very close to zero and nowhere near capable of producing what climate alarmists refer to as the unprecedented warming of the 20th century.  We thus conclude that the surface temperature record on which they rely, i.e., the infamous "hockey stick" reconstruction, is either bogus or that the warming, if real, is due to something quite different from anthropogenic forcing.