What was done
The authors review what they deem to be the salient features of the interacting effects of variations in solar activity and earth's magnetic field on the flux of galactic cosmic rays, together with the likelihood of their potential impact on earth's climate, based on "direct and indirect data on variations in cosmic rays, solar activity, geomagnetic dipole moment, and climate from the present to 10-12 thousand years ago, [as] registered in different natural archives (tree rings, ice layers, etc.)."

What was learned
Dergachev et al. find that "galactic cosmic ray levels in the earth's atmosphere are inversely related to the strength of the helio- and geomagnetic fields," and they conclude that "cosmic ray flux variations are apparently the most effective natural factor of climate changes on a large time scale." More specifically, they note that "changes in cloud processes under the action of cosmic rays, which are of importance for abundance of condensation nuclei and for ice formation in cyclones, can act as a connecting link between solar variability and changes in weather and climate," and they cite numerous scientific studies that indicate that "cosmic rays are a substantial factor affecting weather and climate on time scales of hundreds to thousands of years."

What it means
Carbon dioxide may not be the all-important dominating factor climate alarmists make it out to be when discussing earth's climatic history. Within the context of the Holocene, for example, the only time CO2 moves in concert with air temperature is over the period of earth's recovery from the global chill of the Little Ice Age (the past century or so), and it only does so then quite imperfectly. The flux of galactic cosmic rays, on the other hand, appears to have influenced ups and downs in both temperature and precipitation over the entire 10-12 thousand years of the Holocene, making it the prime candidate for "prime determinant" of earth's climatic state.