By s4n_bl0g. Global Warming. Published at Thursday, January 10th, 2019 - 17:31:34 PM.
The night before the day that would make him famous, James E. Hansen listened to a baseball game on the radio. But his mind kept wandering: What would he say to Congress the next day to convey that humans were endangering the planet?
He had long been trying to raise the alarm without success, and so had other scientists. But then, on June 23, 1988 — 30 years ago Saturday — a Colorado senator named Tim Wirth convened yet another hearing on the topic. Dr. Hansen was one of several scientists on the witness list.
Few people had ever heard of him, nor of the obscure NASA unit that he headed. He and a small group of colleagues studied the Earth’s climate, working in a suite of offices above the Manhattan diner that “Seinfeld” would later make famous.
He had conducted rigorous studies of historical temperatures, concluding that the planet was warming sharply. He had helped to pioneer computer modeling of the climate, and the results predicted further warming if people kept pouring greenhouse gases into the atmosphere.
June 23 turned out be a blistering day in Washington, and much of the nation was suffering through a drought and heat wave. Dr. Hansen took his seat in a Capitol Hill hearing room and laid out the scientific facts as best he understood them.
He had thought up a good line the night before, during the Yankees game, but in the moment he forgot to deliver it. When the hearing ended, though, reporters surrounded him, and he remembered.
“It is time to stop waffling so much,” he said, “and say that the evidence is pretty strong that the greenhouse effect is here.”
His near certainty that human emissions were already altering the climate caught the attention of a sweltering nation, catapulting Dr. Hansen to overnight fame. That year, 1988, would go on to be the hottest in a global temperature record stretching back to the 19th century.
With the perspective of three decades, it is fair to ask: How right was his forecast?
The question defies a simple answer. In 1988, Dr. Hansen had to offer a prognostication not just about how the Earth would respond to greenhouse gases, but also about how much of those gases humans would choose to inject into the air.
He did what any cautious forecaster would do: He offered low, medium and high scenarios. The warming over the past 30 years has indeed fallen well within his upper and lower bounds.
One of Dr. Hansen’s scenarios, Scenario B, has turned out to be a reasonably close match for fossil-fuel emissions as they actually occurred. Yet we now know Scenario B predicted too much global warming, by something like 30 percent.
Two reasons for that stand out. One is that Dr. Hansen had assumed a continued increase in certain refrigerant gases that warm the climate. Those gases were ultimately brought under control by a global treaty, the Montreal Protocol — proof that scientific warnings, if taken seriously, can be acted upon at a worldwide scale.
The bigger problem was that the computers he was using in the 1980s could not operate fast enough to give a realistic picture of the upper atmosphere; as a result, his model was most likely overestimating the Earth’s sensitivity to emissions. In the years since, computer modeling of the climate, though hardly perfect, has improved.
So while his temperature forecast was not flawless, in a larger sense, Dr. Hansen’s 1988 warning has turned out to be entirely on target. As emissions have soared, the planet has warmed relentlessly, just as he said it would; 1988 is not even in the top 20 warmest years now. Every year of this century has been hotter.
The ocean is rising, as Dr. Hansen predicted, and the pace seems to be accelerating. The great ice sheets in Greenland and Antarctica are dumping ever-rising volumes of water into the sea. Coastal flooding is increasing rapidly in the United States. The Arctic Ocean ice cap has shrunk drastically.
If his warning in 1988 had been met with a national policy to reduce emissions, other countries might have followed, and the world would be in much better shape.
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