Meltdown An iceberg calved off one of the glaciers south of Juneau, Alaska, while a rainbow rose over the hillside. (Ian Berry / Magnum Photos)

On a sweltering June day in 1988, James E. Hansen, then the director of NASA’s Goddard Institute for Space Studies, appeared before a key committee of the United States Senate.

Seated before a bank of cameras and a panel of grim officials, Hansen delivered testimony that would start to swing accepted wisdom on the emerging science of climate change.

“I would like to draw three main conclusions,” he began. “Number one, the earth is warmer in 1988 than at any time in the history of instrumental measurements. Number two, the global warming is already large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect. And number three, our computer climate simulations indicate that the greenhouse effect is large enough to begin to affect the probability of extreme events such as summer heat waves.”

The “greenhouse effect,” what we now know as climate change or climate disruption, was caused by human activity, mainly the burning of fossil fuels since the dawn of the Industrial Revolution, said Hansen and other scientists that day.

Colorado Sen. Timothy E. Wirth attended the hearing and in his opening remarks said: “The Energy Committee must move aggressively to examine how energy policy has contributed to the greenhouse effect and the kinds of changes in energy policy that may be needed to reverse the trend of increased emissions of carbon dioxide, a byproduct of the burning of fossil fuels.” Humans, in other words, where driving the warming, and Congress should step in to avoid even more devastating impacts.

At the time of Hansen’s testimony half of the United States was an agricultural wasteland. Meteorologists had declared the worst drought since the Great Dust Bowl. The Mississippi River sank to its lowest level since at least 1872, when record keeping began. The 1980s would become, up to that point anyway, the warmest decade on record. Television screens just a few years earlier beamed images of emaciated figures half a world away, victims of a prolonged drought in the African Sahel. “The Endangered Earth” was Time’s “Planet of the Year.” That climate conditions could cause severe economic damage and deep human suffering was not a huge leap.

Hansen’s forceful testimony about the greenhouse affect wasn’t the first to greet Washington’s political class. As early as 1965, President Johnson was told by his Science Advisory Committee of increasing evidence that human-generated industrial emissions were impacting the atmosphere.

Yet Hansen’s testimony stoked front-page coverage of the issue for the first time and is widely viewed as a turning point in public understanding of human impacts on the climate. The New York Times ran this headline on A1: “Global Warming Has Begun, Expert Tells Senate.” In January 1989, PBS’ NOVA aired “Hot Enough for You?” In the fall of that year, The End of Nature, the first book about the greenhouse effect written for a general audience, hit bookshelves, written by a 29-year-old New Yorker staff writer named Bill McKibben. The media had woken up.

Even if the concept of global warming was rising, it seemed another leap of faith for most outside the scientific community to believe humans could be o profoundly transforming something as vast and seemingly permanent as the Earth’s climate—and do it in as little as one hundred years.

In trying to puncture this idea, Hansen and those like McKibben based their argument simply on science and made their case through explanatory writing. They talked about the ways the greenhouse effect would cause more frequent droughts and the sea levels to rise.

They seemed to make what clearly has proven a naïve assumption: that by presenting only the science, they could provoke swift, determined action to reduce their fossil fuel consumption. Politics was not much on their radar.

McKibben is no longer a staff writer at The New Yorker but he remains a journalist, continuing to publish books and influential articles for Rolling Stone about climate change and the need to quickly curb fossil fuel use. He is most known these days, however, for co-founding 350.org, an organization leading the charge against the Keystone XL pipeline and urging global action on climate change.

“There was a lot of coverage and most of it was smart,” he says by phone from his home in Vermont. “Journalists talked to scientists and just reported it. It hadn’t occurred to them that it should be treated as a political issue as opposed to a scientific one,” McKibben says of coverage in the late 1980s.

Robert S. Eshelman is a Brooklyn, New York-based freelance journalist and associate producer on the Showtime series "Years of Living Dangerously."