This article may be confusing to readers who don’t know the quantitative difference between an ice age and a little ice age, as referred to in the story. During the last ice age, the average cooling in the Northern Hemisphere was about 5C, but the cooling during the last little ice age was only about 0.2C. During the last little ice age, montane glaciers advanced in both hemispheres. However, during the last ice age, much of North America and Europe were covered by glacial ice. This should all be compared with global warming of about 0.6C during the 20th century. Too bad that the next little ice age isn’t expected until the 22nd century.

Paul Damon
Tucson, Ariz.