“This is not a matter of Chicken Little telling us the sky is falling,” Chafee said at the hearing. “The scientific evidence … is telling us we have a problem, a serious problem.”

The hearings garnered considerable media coverage, including on the front page of The Washington Post (see below).

“There is no longer any significant difference of opinion within the scientific community about the fact that the greenhouse effect is real and already occurring,” said newly elected Sen. Al Gore, who, as a congressman, had already held several House hearings on the matter. Gore cited the Villach Conference, a scientific meeting held in Austria the previous year (1985), which concluded that “as a result of the increasing greenhouse gases it is now believed that in the first half of the next century (21st century) a rise of global mean temperature could occur which is greater than in any man’s history.”

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“They were the breakthrough hearings,” remembers Rafe Pomerance, then a staffer with the World Resources Institute, who helped suggest witnesses. “You never saw front-page coverage of this stuff.”

The scientists assembled included some of the voices that would be unmistakable and constant in coming decades. They included NASA’s James Hansen, who would go on to become the most visible scientist in the world on the topic, and Robert Watson, who would go on to chair the soon-to-be formed United Nations’ Intergovernmental Panel on Climate Change.

And what they said was clear: Human greenhouse gas emissions would cause a major warming trend, and sea level rise to boot.

Here’s how the hearings were covered on the front page of The Post:

The New York Times also covered the hearings, writing that “The rise in carbon dioxide and other gases in the earth’s atmosphere will have an earlier and more pronounced impact on global temperature and climate than previously expected, according to evidence presented to a Senate subcommittee today.”

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Two years later, still more famously, Hansen would testify in another series of hearings that had an even greater public impact when it came to consciousness-raising — in part because at that point, he said that the warming of the globe caused by humans was already detectable. “It is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here,” he said then. In 1986, by contrast, scientists were still mostly predicting the future, rather than saying they had measured and documented a clear warming trend — one that could be clearly distinguished from natural climate variability — and that it was already having demonstrable consequences.

“The 1986 testimony is interesting because it was so similar to my 1988 testimony,” Hansen recalls. “I already had, and showed, some of the climate modeling results that formed the basis for my 1988 testimony.”

Granted, in some cases the future temperature projections made in the 1986 hearings — based on assumptions about the rate of increase in greenhouse gas emissions and a high sensitivity of the climate to them — suggested temperatures might rise even more, or even faster, than scientists now believe they will. By email, Hansen clarified that we now know the world is closer to one scenario he presented in 1986 — called Scenario B — than to Scenario A, which assumed a much more rapid rate of greenhouse gas growth, and accordingly, much faster warming.

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Still, the theoretical understanding was in place for why temperatures would rise as greenhouse gases filled the atmosphere — simply because scientists knew enough physics to know that that’s what greenhouse gases do.

“We knew in the ’70s what the problem was,” said George Woodwell, founding director of the Woods Hole Research Center, who also testified in 1986. “We knew there was a problem with sea level rise, all disruptions of climate. And the disruptions of climate are fundamental in that they undermine all the life on the Earth.”

Much of the formal understanding had been affirmed by a 1979 report by the U.S. National Academy of Sciences, led by the celebrated atmospheric physicist Jule Charney of the Massachusetts Institute of Technology. That group famously assessed that if carbon dioxide levels in the atmosphere were to double, the “most probable global warming” would amount to 3 degrees Celsius, with a range between 1.5 degrees and 4.5 degrees, a number quite similar to modern estimates.

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“We have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO2 to negligible proportions or reverse them altogether,” the scientists behind the report wrote.

Indeed, the fundamental understanding of the greenhouse effect, and that carbon dioxide is a greenhouse gas because of its particular properties, dates back to the 19th century, when the Irish scientist John Tyndall conducted experiments to determine the radiative properties of gases.

No wonder, then, that there was so much that scientists could say about it in 1986. And indeed, if you look at global temperature trends, it turns out they were speaking at a time when the planet’s temperatures were beginning a steady upswing, one that, despite various yearly deviations, would continue inexorably to the present:

“This hearing helped bring the concern together, and essentially painted a picture that things are kind of spinning out of control, that science is trying to tell us something, that the world seems to be changing even faster than our scientific understanding of the problem, and worst of all, our political leaders are way behind the eight ball,” said Michael Oppenheimer, a Princeton climate scientist who testified that day, and argued that action was warranted on climate change even though not everything was known about its consequences.

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“I have to say, reading my own testimony … you know, I’d stick by everything in that today, even though it’s 30 years later,” Oppenheimer said.

There was an additional context, though, that we’re now less conversant with: The hearings were also about the issue of the depletion of the Earth’s protective ozone layer by chlorofluorocarbons, or CFCs. Scientists had recently discovered an “ozone hole” over Antarctica that frightened the public, and seemed a definitive indicator of just how much human activities could change the atmosphere.

Even today, some still confuse the issue of climate change with that of the depletion of the ozone layer. They are not the same, but they are closely related in that both showed how seemingly small actions by individual humans, or by human industry, could add up to planetary consequences.

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However, the ozone problem would prove far easier to fix. In 1987, just a year later, the nations of the world adopted the Montreal Protocol, which is today regarded as a major success in environmental protection. Under the treaty, a flexible and adaptable approach was taken to reductions — and regular scientific assessments allowed for course adaptation based on the latest information about how well progress was proceeding. Thus, by 2007, the U.N. Environment Program could declare of the treaty that “to date, the results of this effort have been nothing less than spectacular.”

The contrast with climate change is stark. Despite having been alerted by scientists not only in 1986, but also in 1979 and, frankly, even earlier, what happened was not policy action, but rather the beginnings of a long political battle.

Even as the formation of the U.N. Intergovernmental Panel on Climate Change in 1988, and the global adoption of the Framework Convention on Climate Change in 1992, signaled steps toward action in the scientific and diplomatic communities, skeptical scientists emerged to challenges the views expressed by Hansen and others, supported by conservative think tanks and sometimes linked to fossil fuel interests. Meanwhile, U.S. politics shifted, as over the 1990s and especially the 2000s the climate change issue became polarized and it became rarer to see Republicans, such as Chafee, who were also strong environmentalists and advocates for climate action.

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“Thirty years ago we had a Republican senator who was leading the charge on addressing what he said then was a real and serious threat of climate change from the emission of gases from fossil fuel burning,” says Sen. Sheldon Whitehouse (D-R.I.), recalling the 1986 hearings. “You can read through all the things that Senator Chafee said back then, and it has all been proven true. It’s very disappointing that thirty years later, there is no such voice anywhere in the Republican Senate, and if you look for a micron of daylight between what the fossil fuel industry wants, and what the Republican Party in the Senate does, you won’t find it.”

It was only in late 2015, in Paris, that the United States helped to negotiate a global agreement to address climate change, one in which each country sets its own pace on reducing emissions. But scientists widely agree that this accord isn’t strong enough, on its own terms, to ensure that warming remains below a 2-degree Celsius danger zone.

Thirty years after the 1986 hearings, meanwhile, presumptive Republican presidential nominee Donald Trump said that if elected, he would attempt “renegotiating” that agreement.

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“Those agreements are one-sided agreements, and they are bad for the United States,” Trump said.

CORRECTION: Due to an editing error, this post stated an incorrect temperature-increase value in Fahrenheit.

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