Hansen vs The World (Part 1)

A Climate Awakening

Dec 09, 2024

In the mid-1980s, it was becoming evident that the Earth’s climate was changing and humanity was a driving force. However, there were also many uncertainties regarding the rate and magnitude of climate change impacts globally. For politicians, the emerging science of a warming planet presented not only a scientific dilemma but also a tough political challenge. Climate science intersected with politics in complex ways. Early debates about humanity’s influence on the planet’s climate intersected with other pressing issues of the time. For example, in the early 1980s, climate science found itself entangled with opposition to the Reagan administration’s nuclear weapons policy. Carl Sagan and other scientists had sounded alarms about the devastating potential of a “nuclear winter” if atomic weapons were ever used. Although this was a different scenario from the greenhouse effect, it underscored the grim potential for severe, global-scale disruptions to climate—even if from a different perspective.

As awareness of climate risks grew, the U.S. House of Representatives began paying serious attention, thanks in part to the efforts of then-Congressman Al Gore. On the Senate hearing on the greenhouse effect and climate change on 10 and 11 June 1986, NASA scientist Robert Watson made a declaration that captured the urgency of the moment. “I believe global warming is inevitable”, he declared. “It is only a question of the magnitude and the timing”. His statement appeared the next day on the front page of the major papers, transforming a relatively obscure scientific topic to national prominence.

Among the scientists who testified that June was Dr. James Hansen, head of NASA’s Goddard Institute for Space Studies. Hansen predicted that within 15 years, global temperatures would rise “to a level which has not existed on Earth in the past 100,000 years.” Soon, he would become one of the most recognisable voices in the climate debate.

Watson’s and Hansen’s predictions painted a bleak picture, yet they were met with a mix of urgency and skepticism. And despite the efforts to build a consensus on climate action, political unity proved elusive. Senator John Chafee (R-RI), summarised the hearings as “It was the scientists yesterday who sounded the alarm, and it was the politicians, or the government witnesses, who put the damper on it”. Roger A. Pielke Jr. writes that “Chafee’s comments were an accurate characterization of the developing relationship between many in Congress who sought to heed the scientists’ alarm and those in the executive branch who tried to dampen it.”

“It's just a logical conclusion that the greenhouse effect is here."

Yet, two years later, the debate shifted dramatically. On June 23, 1988, a sweltering day in Washington, D.C., James Hansen returned to the Capitol and made history. Testifying before Congress, he declared with a 99% statistical certainty that greenhouse warming “is happening now”. (Hansen, , et al., 1988)

Dr James Hansen - US senate 23 June 1988

In the same month, the United States experienced one of its worst droughts in history, which significantly affected the Midwest and the Great Plains, regions critical to U.S. agriculture. This devasting drought led to widespread agricultural losses, water shortages, and economic disruption.

In ‘Sophie’s Planet’, Hansen details the preparation of his testimony, highlighting three main conclusions:

Record High Temperatures: 1988 was on track to be the warmest year on record, with the four warmest years occurring in the 1980s.
Greenhouse Effect Attribution: The warming trend could be attributed with high confidence to the greenhouse effect caused by human activities.
Model Predictions: Climate models predicted an increase in the frequency and severity of extreme weather events, such as heatwaves and droughts, if greenhouse gas emissions continued to rise.

During his now-famous testimony, James Hansen presented early climate model predictions that forecasted significant global warming if human emissions of greenhouse gases, such as CO2 and methane, continued to rise. His predictions went beyond averages; they foretold a future where extreme weather events, like heatwaves and droughts, would become more frequent and severe.

“We are loading the climate dice,” Hansen said during his testimony, arguing that the climate models had become reliable enough to conclude that rapid strengthening of the greenhouse effect would “lead to drought intensification at most middle and low-latitude land areas.” It was a major moment in the history of climate science, as it helped shape how we think about the reliability of climate predictions. (Schmidt, 2007)

“Altogether the evidence that the earth is warming by an amount which is too large to be a chance fluctuation, and the similarity of the warming to that expected from the greenhouse effect, represents a very strong case, in my opinion, that the greenhouse effect has been detected, and it is changing our climate now.” _ James E. Hansen

J. Bennett Johnston, the Democratic Senator from Louisiana and chairman of the Senate Committee on Energy and Natural Resources, opened the hearing proceedings with a one-liner that quickly made headlines, “We have only one planet. If we screw it up, we have no place to go.” And he continued, “The greenhouse effect has ripened beyond theory now. We know it is a fact. What we don’t know is how quickly it will come upon us as an emergency fact, how quickly it will ripen from just simply a matter of deep concern to a matter of severe emergency.”

In the original 1988 paper, Hansen outlined three scenarios for future emissions. They were based on different assumptions about how much greenhouse gas emissions would grow:

Scenario A assumed emissions would keep increasing rapidly.
Scenario B assumed a steady, slower increase in emissions.
Scenario C assumed emissions would level off around the year 2000.

The scenarios also included guesses about other factors like volcanic eruptions, which can temporarily cool the planet by blocking sunlight. Hansen believed Scenario B was the most realistic of the three.

Figure 2: Climate model calculations reported in Hansen et al. (1988). The figure presented by Hansen shows the simulated global mean temperature for three climate-forcing scenarios. Scenario A has a fast growth rate for greenhouse gases. Scenarios B and C have a have a moderate growth rate for greenhouse gases until the year 2000, after which greenhouse gases stop increasing in Scenario C. Scenarios B and C also included occasional large volcanic eruptions, while scenario A did not.

Hansen did not utter the terms “fossil fuels” or “petroleum” in his testimony. Nonetheless, everyone in the room understood that the global warming he described could not be addressed without taking on, as Arkansas Democratic senator Dale Bumpers pointed out, “the industries that produce the things that we throw up in the atmosphere.” His candid remark “… what you have is the economic interests pitted against our very survival,” remains as relevant today as it was in 1988.

This statement highlighted the significant challenge of addressing climate change in the context of powerful industrial and economic forces resistant to change. Senator Bumpers acknowledged that effective climate action requires confronting major industries responsible for greenhouse gas emissions, such as fossil fuels and manufacturing, whose interests often dominate political and economic decision-making.

Dale Bumpers made another strong statement that proved prescient, indeed, it sounded like an instruction to all the media in attendance: “Dr. Hansen is going to testify today to what…ought to be cause for headlines in every newspaper in America tomorrow morning.”

Later, after the hearing, as Hansen stood surrounded by reporters in the Capitol hallway, he delivered a line that not only made the next day’s headlines but also resonated for decades to come. “It is time to stop waffling so much,” he said, “and say that the evidence is pretty strong that the greenhouse effect is here.”

The New York Times cover page on 24 June 1988

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