A climate hero: The early years

Originally posted at Grist.com

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A look back at James Hansen's seminal testimony on climate, part one

The speakers at a Washington, D.C., climate rally this past Earth Day, April 22, showcased the range of the modern environmental movement. They included an activist who engaged in a hunger strike, an outspoken preacher from the Hip Hop Caucus, and a folk duo that performed, "Unsustainable," a parody of Frank Sinatra's "Unforgettable."

Yet it was a comparatively dry, 20-minute scientific presentation that brought the crowd to its feet. The speaker, introduced as a "climate hero," was James Hansen, a long-time scientist with the U.S. National Aeronautics and Space Administration.

Hansen is not a revolutionary by character. He is a mild-natured man who speaks with a soft, Midwestern tone. Raised in southwest Iowa, the fifth child of tenant farmers, Hansen would later commit his life to studying computerized climate models. With human-induced climate change now widely regarded as the greatest challenge of this generation, Hansen is considered a visionary pioneer.

Theories of climate change first surfaced more than a century ago. But it was Hansen who forever altered the debate on climate change 20 years ago this month.

On June 23, 1988, in the sweltering heat, Hansen told a U.S. Senate committee he was 99 percent certain that the year's record temperatures were not the result of natural variation. It was the first time a lead scientist drew a connection between human activities, the growing concentration of atmospheric pollutants, and a warming climate.

"It's time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here," Hansen told reporters.

Scientists first expressed concern about possible climate change more than a decade before Hansen's testimony. The most-publicized report came from the National Academy of Sciences in 1977. It warned that average temperatures may rise 6 degrees Celsius by 2050 due to the burning of coal.

Around the same time, Hansen, a space scientist at NASA's Goddard Institute for Space Studies in New York, began studying the effect of greenhouse gases on climate. His first paper on the subject, published in the journal Science (PDF) in 1981, predicted that burning fossil fuels would increase global temperatures by 4.5 degrees Fahrenheit (2.5 degrees Celsius) by the end of the 21st century.

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