Jim Hansen’s life changed on the evening the moon disappeared completely. In a building in a cornfield Jim and fellow University of Iowa students Andy Lacis and John Zink, and their professor Satoshi Matsushima, peered in surprise through a small telescope into the wintry sky. It was December 1963, and they had seen the moon replaced by a black, starless circle during a lunar eclipse. The moon always passes into Earth’s shadow during such eclipses, but usually you can still see it.
At first they were confused, but then they remembered that in March there had been a big volcanic eruption. Mount Agung in Indonesia had thrown tonnes of dust and chemicals into the air: perhaps that was blocking out the little light they’d normally have seen? With a spectrometer attached to their telescope they measured the moon’s brightness, data Jim would then base his first scientific research on. Using this record to work out the amount of ‘sulphate aerosol’ particles needed to make the moon disappear, Jim began a lifelong interest in planets’ atmospheres. That would lead him to become director of the NASA Goddard Institute of Space Studies (GISS), where he has led the way in exposing the threat from human CO2 emissions.
Jim was born in Iowa in 1941, the fifth of seven children of a farmer, who had left school at 14, and his wife. As he grew up they moved into the town of Denison, his father becoming a bartender and his mother a waitress, and Jim spending his time playing pool and basketball. Jim claims he wasn’t academic, but found maths and science the easiest subjects, always getting the best grades in them in his school. Though his parents divorced when he was young, public college wasn’t expensive at the time, meaning Jim could save enough money to go to the University of Iowa.
The university had an especially strong astronomy department, headed by James Van Allen, after whom brackets of space surrounding the Earth are named. These ‘Van Allen Belts’ are layers of particles that he discovered, held in place by the planet’s magnetic field. Satoshi Matsushima, a member of Van Allen’s department, could see Jim and Andy’s potential and convinced them to take exams to qualify for PhD degrees a year early. Both passed, with Jim getting one of the highest scores, and were offered NASA funding that covered all their costs.
A few months later, it was Satoshi who suggested measuring the eclipse’s brightness, feeding Jim’s interest in atmospheres on other planets. “Observing the lunar eclipse in 1963 forced me to think about aerosols in our atmosphere,” Jim told me. “That led to thinking about Venus aerosols.” In an undergraduate seminar course Jim had given a talk about the atmospheres of outer planets, which James Van Allen had attended. The elder scientist told him that recently measured data was suggesting Venus’ surface was very hot. Aerosols stopped light reaching the Earth during the eclipse – could they be warming up Venus by stopping heat escaping, Jim wondered? That would become the subject of his PhD, and Satoshi and James Van Allen would be his advisors.
What Venus infers
Working out how aerosols affected Venus’ climate would take detailed calculations on early computers of how heat energy passed through its atmosphere. One option, breaking the atmosphere down into thin layers and then adding them together, had been developed by Sueo Ueno at the University of Kyoto. Satoshi got a grant to study in Japan, and took Andy and Jim with him. While in Japan, Jim applied for a research post at NASA GISS, got it, and suddenly found himself with an imminent deadline for his thesis. Pressed for time, Jim turned to supercomputer-based models developed the US National Oceanic and Atmospheric Administration (NOAA)’s Suki Manabe, which used single columns of gases and aerosols to represent a whole planet’s atmosphere. But even that was too complex and time consuming. To finish his PhD in time to start his new job, Jim was left to rely mainly on his own calculations and intense focus.
Starting at GISS – located right above Tom’s Restaurant in Manhattan, made famous by Suzanne Vega and Seinfeld – in 1967 Jim now had access to a much bigger computer. That meant he could continue improving our understanding of Venus’ atmosphere, a topic he stuck with until the early 1980s. He had been hired to look at how light and other radiation warmed planets, including how scattering by aerosols interfered with this process. In 1969 that quest sent him on a year-long stint to Leiden, the Netherlands, where he met his wife Anniek. However GISS director Robert Jastrow invited Jim back to lead the design of an instrument to go on a NASA Pioneer probe destined for Venus. After just six months in the Netherlands, and briefly honeymooning and watching an Apollo launch in Florida, Jim returned to New York.
In 1971 Jim’s GISS coworkers Steve Schneider and S. Ichtiaque Rasool used the new methods to make a controversial and long-remembered prediction of global cooling. They’d wrongly assumed that man-made aerosol pollution would spread across the world, reflecting the Sun’s warmth back into space, while their oversimplified model underestimated CO2’s greenhouse effect. But Jim’s fellow eclipse observer Andy Lacis was now working at GISS, and as part of a larger team the pair devised a new model that would soon help underline the error. Built from scratch and perhaps reflecting Jim’s PhD struggles, it was at least ten times as fast as other methods.
Published in 1974, the new model found the amount of warming at Earth’s surface caused by a doubling of CO2, known as climate sensitivity, would be around 4°C. That was double the figure that came out of Suki Manabe’s NOAA model and so, in 1979 a US government-commissioned report split the difference between them. Predicting that CO2 levels in the air would double over the next century, it forecast temperatures would rise by 3°C, plus or minus 50%, giving a range from 1.5-4°C.
We can send a probe to Venus, but can we understand Earth’s climate?
The increasing power of climate models to explore and explain processes on Earth inspired Jim to return to the eclipse data he’d collected in Iowa. “I tried to use the Agung volcanic aerosols as a test of our understanding of global climate forcing and planetary response,” he told me. He found good agreement between modelled temperatures and observations, but was cautious about that result as at the time there was no temperature dataset that spanned the entire world.
With Jim’s interest in Earth’s climate growing, he came to the tough decision that he would have to resign from the Pioneer Venus mission. He felt obliged to ask University of Arizona’s Donald Hunten, the mission’s ‘father’, for permission. The gruff response he got back was at once cryptic and a career-defining moment. “Be true to yourself,” Donald had said.
Now free to look closely at Earth’s temperature data, Jim found that gaps in available records were not as much of a problem as people had thought. Measurements hundreds of miles apart were closely linked, and on that basis they built a global record showing 0.2°C warming from the mid-1960s to 1980 and around 0.4°C over the previous century. This was just what the GISS climate models predicted should have happened thanks to human CO2 emissions. On that basis Jim, Andy and their coworkers projected 3-4.5°C warming by 2100 if energy use grew rapidly. “The degree of warming will depend strongly on the energy growth rate and choice of fuels for the next century,” they wrote in the 1981 Science paper describing their findings. “Thus, CO2 effects on climate may make full exploitation of coal resources undesirable.”
As this work was unfolding, GISS director Robert Jastrow invited Jim for lunch with Walter Sullivan, the New York Times science reporter, at the Moon Palace, a Chinese restaurant opposite their offices. “He took me along to talk about a proposed mission to the outer planets,” Jim told me. “I thought that I should send him the thing that I was really working on.” Walter and his editors found our impact on the planet so striking the story put the greenhouse effect on the front page for the first time. A follow-up editorial declared that radical energy policy change might become necessary.
Soon afterwards Jim would replace Robert as GISS director, but that didn’t mean he avoided a bad reaction. Ichtiaque Rasool, by then working in Paris, suggested Hansen had emphasised ‘the worst case in order to get the attention of the decision makers who control the funding’. “Somehow Ichtiaque got a burr under his saddle,” Jim recalled. “Several people asked me what was going on with him, and one suggested that he was jealous of the publicity the paper got – and he didn’t like the conclusion that greenhouse gases overwhelmed the effect of aerosols.” The accusation of using exaggeration to greedily grasp for cash is still directed at climate scientists today by people suspicious of their motives.
The headlines in fact had the opposite effect, driving the US Department of Energy to withdraw promised funding for GISS, and forcing Jim to lay off five researchers. But despite this setback, and a shyness that often makes it hard for him to talk, Donald Hunten’s advice would stay with him. As his understanding of the threat from climate change grew, Jim would speak out with increasing force, becoming the loud and often controversial voice for action he remains today.
- This is the first part of a profile of Jim Hansen. Read part two here.
I’ve already written about the following pivotal climate scientists who came before Jim Hansen, or were around at the same time: Svante Arrhenius, Milutin Milanković, Guy Callendar part I, Guy Callendar part II, Hans Suess, Willi Dansgaard, Dave Keeling part I, Dave Keeling part II, Wally Broecker part I, Wally Broecker part II, Bert Bolin part I, Bert Bolin part II, Suki Manabe part I, Suki Manabe part II, Steve Schneider part I, Steve Schneider part II, Steve Schneider part III
I got the main outline of Jim’s life and inspiration from his book, ‘Storms of my Grandchildren’.
Most details of Jim’s early career come from Spencer Weart’s interviews with him, conducted in the year 2000 and now hosted by the American Insitute of Physics’ Oral Histories Project. Others come from profiles by Elizabeth Kolbert in the New Yorker in 2009 and by David Herring on the NASA Earth Observatory website from 2007.
Matsushima, S., Zink, J., & Hansen, J. (1966). Atmospheric extinction by dust particles as determined from three-color photometry of the lunar eclipse of 19 December 1963 The Astronomical Journal, 71 DOI: 10.1086/109863
Hansen, J., & Matsushima, S. (1967). The Atmosphere and Surface Temperature of Venus: a Dust Insulation Model The Astrophysical Journal, 150 DOI: 10.1086/149410
Somerville, R.C.J., P.H. Stone, M. Halem, J.E. Hansen, J.S. Hogan, L.M. Druyan, G. Russell, A.A. Lacis, W.J. Quirk, and J. Tenenbaum (1974). The GISS model of the global atmosphere J. Atmos. Sci. DOI: 10.1007/BFb0019776
HANSEN, J., WANG, W., & LACIS, A. (1978). Mount Agung Eruption Provides Test of a Global Climatic Perturbation Science, 199 (4333), 1065-1068 DOI: 10.1126/science.199.4333.1065
Hansen, J., Johnson, D., Lacis, A., Lebedeff, S., Lee, P., Rind, D., & Russell, G. (1981). Climate Impact of Increasing Atmospheric Carbon Dioxide Science, 213 (4511), 957-966 DOI: 10.1126/science.213.4511.957
Rasool, S. (1983). On predicting calamities Climatic Change, 5 (2), 201-202 DOI: 10.1007/BF00141271
Spencer Weart’s book, ‘The Discovery of Global Warming’ has been the starting point for this series of blog posts on scientists who played leading roles in climate science.