text: At the heart of the paper, Solar Forcing of the Polar Atmosphere, are calcium, nitrate and sodium data from ice cores collected in four Antarctic locations and comparisons of those data to South Pole ice core isotope data for beryllium-10, an indicator of solar activity. The authors also point to data from Greenland and the Canadian Yukon that suggest similar relationships between solar activity and the atmosphere in the northern hemisphere. They focus on years since 1400 when the Earth entered a roughly 500-year period known as the Little Ice Age.