In a Jan. 11 letter, one of your readers defined scientific data and then asserted that “scientists who maintain that carbon dioxide and methane are the principal causes of global have no such data to present.”

This assertion is utterly false. Climate scientists have accumulated mountains of data on concentrations of greenhouse gases and their history, on variations in solar intensity, on fluctuations in ocean currents, on variations in the Earth’s orbit — in short, on every aspect of the complex and fascinating planetary climate system. Their near-unanimous conclusion after analyzing all these data is that the main reason for the observed global warming is human-caused changes in the atmosphere, principally the increase in carbon-dioxide emissions caused bt burning of fossil fuels such as coal, oil, and gas.

The climate is indeed changing, but we can do something about it, because we are its cause.

William E. Williams, Dameron

The writer is professor emeritus of biology at St. Mary’s College of Maryland.