What was done
The authors assembled a wide range of lacustrine, tree-ring, ice-core and marine records that reveal a Northern Hemispheric - and possibly global - cooling event of less than 200 years duration with a 50-year cooling-peak centered at approximately 10,300 years BP. They then searched for signs of various forcing factors that might have been the cause of this dramatic climatic excursion.

What was learned
The onset of the cooling event broadly coincided with rising ¹⁰Be fluxes, which are indicative of either decreased solar or geomagnetic forcing; and since the authors note that "no large magnetic field variation that could have caused this event has been found," they postulate that "the ¹⁰Be maximum was caused by distinctly reduced solar forcing."  They also note that the onset of the Younger Dryas is coeval with a rise in ¹⁰Be flux, as is the Preboreal climatic oscillation.

What it means
Although the case for reduced solar irradiance being the cause of the cooling event at 10,300 years BP is by no means iron-clad, the several temporal correspondences between fluctuations in ¹⁰Be flux and shifts in hemispheric/global climate recorded in the geologic record of the Holocene is an important empirical push in that direction.  Just a couple more nudges and we should arrive at the seemingly inevitable conclusion that earth's climate on sub-Milankovitch timescales is tightly coupled to variable solar activity.