The witness who collided with government on climate

• This is part two of this profile. Read part one here.

Jim Hansen giving testimony at a US Congressional hearing in 1988, where he’d declare 99% certainty that humans are changing the climate. Image credit: NASA

“It’s time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here.” It’s a comment that wouldn’t sound out of place today, but Jim Hansen made it 26 years ago, on June 23, 1988, amid record 38°C temperatures in Washington DC. Jim said it to reporters after telling a Congressional hearing he was 99% certain the world is getting warmer thanks to human-made greenhouse gases.

Jim’s 1980s media bombshells led journalist Robert Pool to liken him to a religious ‘witness’, ‘someone who believes he has information so important that he cannot keep silent’. However, he still felt shy and awkward, preferring to immerse himself in pure science, and so would turn down almost all invitations to speak out for another decade. Jim’s efforts during that period would then help build even stronger evidence on global warming. But with extra motivation provided by clashes with the US government and the arrival of his grandchildren he would return to bear witness more forcefully than ever.

Before his self-imposed media ban Jim would make headlines one more time in 1989, after giving written evidence to a hearing convened by then US senator Al Gore. The testimony reaching the hearing had been altered by the White House to make his conclusions about the dangers of global warming seem less certain. When Jim sent the future vice-president a note telling him this, he alerted the media, turning their scheming into the lead story across all TV networks that evening. John Sununu, aide to then president George H. W. Bush, would then try to get Jim fired for his troubles. But Republican senator John Heinz intervened on Jim’s behalf, and he kept his job.

The reputation Jim had built up as a warming witness went ahead of him in December 1989, as he walked into a ‘roundtable’ meeting held by senators Al Gore and Barbara Mikulski. On the coldest day of the year, in a building whose heating system had failed, Al noticed Jim enter and said, “Hey, aren’t you the guy who…” Despite such jibes, Jim was becoming firmer in his convictions. In April 1990 he offered a group of climatologists an even money bet that one of the next three years would be the warmest in a century. He’d be proven right by the end of the year.

How lessons from space put the greenhouse effect on the front page

Normally during a total lunar eclipse, like this one on April 15, 2014, you can still see the moon, but in 1963 Jim Hansen saw it disappear completely. Explaining why would send him on a scientific journey to Venus, before coming back down to Earth. Image credit: NASA

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.

The ice-age U-turn that set the stage for the climate debate

Steve Schneider (left), Jim Hansen (centre), and S. Ichtiaque Rasool (right) at NASA Goddard Institute for Space Studies in New York, circa 1971. Image copyright: Stephen H. Schneider

On 13 July 1971, world-leading researchers gathered in Stockholm, Sweden, concluded their presentations about human influence on climate, and opened the meeting to questions from the press. But rather than asking about the most important climate meeting yet, the assembled reporters first looked to the meeting’s 26-year old secretary. “Where is Dr. Schneider? When is the ice age coming?” they asked.

The journalists sought out Stephen Schneider about a paper by him and his NASA Goddard Institute for Space Studies (GISS) boss, S. Ichtiaque Rasool, published just four days before. Using early computer models, they warned of a scenario where enough dusty aerosol pollution could be ‘sufficient to trigger an ice age’. For Steve, this would be the first encounter of many with the media’s interest in climate, leading him ultimately to help define how scientists influence the wider world.

As a PhD student at Columbia University in New York in the late 1960s, Steve came into contact with some of the world’s leading experts on climate. Wally Broecker, who at that time was helping establish the timing of the ice ages, lectured him on oceanography. A talk by Joe Smagorinsky from the US National Oceanic and Atmospheric Administration (NOAA), who was establishing some of the first computer climate models with Suki Manabe, played on Steve’s childhood fascination with hurricanes. And when he took a seminar by Ichtiaque talking about planets’ atmospheres – why Mars was too cold, Venus too hot, and Earth just right – he was hooked.

While writing up his PhD thesis he got a part-time job with Ichtiaque, tackling a key question at the time. Burning fossil fuels creates two types of pollution that influence climate – warming CO2 and cooling aerosols. But which one would win out? On the advice of fellow GISS scientist Jim Hansen, Steve used a method partly developed by astronomer Carl Sagan to calculate the aerosol effect. He put this into a model of warming from CO2 Ichtiaque gave him. They found that doubling CO2 levels in the air would raise temperatures by about 0.7°C – much lower than Suki’s earlier estimate of 2°C for this ‘climate sensitivity’ figure. But models where aerosols were spread everywhere experienced 3-5°C cooling, prompting Ichtiaque to write the ice age comment, referring to other controversial research of the time.

Ichtiaque had asked Steve to handle criticism of the study, but in the meantime Steve had managed to get an invite to the Stockholm gathering of leading climate scientists. Being a ‘rapporteur’ he was supposed to only be taking notes at the three week Study of Man’s Impact on Climate (SMIC) meeting, organised by Bert Bolin. But Steve couldn’t resist showing Suki some of his modelling work on clouds’ role in climate – and then the aerosol study was published. Ichtiaque had mischievously told a reporter that Steve was presenting the work at SMIC, forcing his young colleague to give a brief seminar, and face the press.

The man who got the world to agree on climate

• This is part two of a two-part post. Read part one here.

When not tackling climate science or negotiations Bert Bolin liked nothing more than a little choir singing. Credit: KVA

In 1975, advised by Bert Bolin, the Swedish government drafted a bill on future energy policy containing a conclusion that elsewhere might be controversial even today. “It is likely that climatic concerns will limit the burning of fossil fuels rather than the size of the natural resources,” it foresaw. Produced thanks to Bert’s early role tackling environmental issues, it was one of the first times humans’ effect on climate and the risk it poses us was noted officially. For more than two decades afterward the Stockholm University researcher would further strengthen that case, both through his research and by putting climate science firmly on the political agenda. And those tireless efforts would help the United Nations’ Intergovernmental Panel on Climate Change (UN IPCC) to consistently achieve what otherwise might have been impossible agreements.

The Swedish bill was a bold statement, given that average air temperatures were only just about to reverse a slight cooling that had gone on since 1940. Bert and scientists like Dave Keeling had shown that CO2 levels in the atmosphere were rising. Basic science established by Svante Arrhenius 80 years before had showed this should warm Earth’s surface. So why was it cooling? The way scientists found the answer was typical of the progress in climate science Bert was overseeing. They would use the latest tools, including computers and satellites, bringing theory and measurement together to improve our understanding.

Climate models in the early 1970s were still simple by today’s standards, but had advanced from the early computerised weather predictions Bert had previously pioneered. And when Columbia University’s Stephen Schneider and S. Ichtiaque Rasool added aerosols of floating dust to CO2 in a model for the first time, they found a possible explanation for the temperature drop. The aerosols, particularly human pollution, created a cooling effect that swamped the warming – so much so they warned it could trigger an ice age. Though Stephen and Ichtiaque soon realised that their model overestimated the cooling, aerosols obviously deserved a closer look.

To clear up such murky problems, the Global Atmospheric Research Programme (GARP) that Bert jointly set up would bring together scientists from around the world, despite the cold war. As GARP’s first experiments, looking at heat and moisture flow between the atmosphere and ocean, started in 1974, Bert organised a meeting in Stockholm on climate physics and modelling. GARP had two goals – improving 6-10 day weather forecasts first, and climate change predictions second. As it gradually became clear how hard the first was, climate forecasting became more important.

Diplomacy was needed among the gathered scientists as arguments flared over how ambitious they should be. Should they strive for satellites that could collect the high resolution data scientists and models needed, even though that was beyond their capabilities at the time? And significantly for later climate work – should they seek to produce results so society could respond to change, even when results were uncertain? Bert was clear on that one: scientists had to answer socially important questions, though he was in a very small minority prepared to say so openly.

Volcano cloud over tree-ring temperatures clears

Pennsylvania State University’s Michael Mann thinks he has found the reason behind key outstanding disagreements between the historical temperature record based on tree rings and climate models for the same period. Credit: Pennylvania State University

The sudden chills violent volcano eruptions cast over the world centuries ago effectively erased themselves from the historical climate record produced by examining tree-rings. So suggests a team led by Michael Mann from Pennsylvania State University, who famously used 1,000 years of tree-ring measurements in the “hockey stick” graph showing how unusual today’s temperatures are. Michael warns the skipped years could affect scientists’ estimates of how much the world warms in response to greenhouse gases in the atmosphere, known as its climate sensitivity. But other than the volcano years, the scientist notes that tree-ring data is a remarkably accurate match with the climate models they used for comparison. “Interestingly, the effect has little influence on long-term trends, including conclusions about how previous temperatures compares to modern ones,” he told me. “Instead, it appears only to have implications for how strong past short-term cooling events were.”

A tree’s age can usually be told from the rings that form across its trunk representing each year’s growth. How thick each ring is shows how much the tree grew in the year in question, which is influenced by the temperatures that tree experienced. That means examining the thickness of rings in old trees can provide a way to tell temperatures back through history. Many challenges have already been overcome in turning this simple-sounding idea into a history of the world’s temperature, but Michael was still troubled by one particular detail.