Judith Lean and David Rind

In the following viewpoint, Judith Lean and David Rind assert that the role of a variable sun in global warming accounts for, at best, one-half of the recorded warming since 1850 and less than one-third of the warming observed over the last twenty- five years. The most likely cause of climate change since the start of the Industrial Revolution 150 years ago, according to the authors, is the growing atmospheric concentration of greenhouse gases originating from human activity. Judith Lean is a solar physicist at the U.S. Naval Research Laboratory in Washington, D.C. David Rind is a physicist at the NASA Goddard Institute for Space Studies in New York City.

As you read, consider the following questions:

1. According to the authors, who discovered that sunspots come and go in eleven-year cycles?
2. What...