Geologist Paul Hoffman looks over rock samples in his office in Victoria, B.C., on Nov. 3. He has received the Kyoto Prize, which is handed out for outstanding contributions to science, technology, philosophy and the arts.Chad Hipolito/The Globe and Mail
Paul Hoffman says he wasn’t a very good student at his Toronto high school in the 1950s. It didn’t help that he refused to do homework.
“I had so many other more interesting things to do with my time,” he said.
He was right. Now 83, Dr. Hoffman is a celebrated geologist and a professor emeritus at Harvard University who is best known for rewriting a crucial part of our planet’s history.
On Monday, he received the Kyoto Prize in recognition of his achievements. The international award, worth 100-million yen (about $900,000), is given annually by Japan’s Inamori Foundation for outstanding contributions to science, technology, philosophy and the arts.
Dr. Hoffman, who lives in Victoria, is the third Canadian to win the prize. He was honoured at a ceremony alongside British physicist John Pendry and American dancer and choreographer William Forsythe. But few recipients, past or present, have worked on as big a canvas.
He is best known for his work on the snowball Earth hypothesis – the idea that our planet has, at various times, been encased in a global ice age from equator to poles. Evolutionary biologists have speculated that this may have set the stage for the first flourishing of early animal life.
Today, snowball Earth is increasingly accepted by scientists, though many details remain to be worked out. But it was initially seen as so controversial a claim that Dr. Hoffman said he had a hard time believing it himself.
The making and unmaking
of snowball Earth
In a snowball Earth scenario, the growth of glaciers at the poles increases the amount of sunlight that is reflected into space. This cools the planet, allowing glaciers to grow even larger. As temperatures plunge, the entire planet is encased in ice. This persists until carbon dioxide from volcanic eruptions builds up in the atmosphere and gradually brings Earth's temperatures back to the melting point of ice. Once ocean water is exposed at the equator, the planet rapidly transitions into a hot phase. The temperature later returns to its starting point after enough carbon dioxide has been scrubbed from the atmosphere through the formation of carbonate minerals.
Global average
surface temperature
(celsius)
How the Earth may have looked
-40
-20
0
20
40°C
0
Elapsed time since onset of snowball Earth (millions of years)
1
2
3
4
5
6
MURAT YÜKSELIR / THE GLOBE AND MAIL,
SOURCE: TERRA NOVA
The making and unmaking of snowball Earth
In a snowball Earth scenario, the growth of glaciers at the poles increases the amount of sunlight that is reflected into space. This cools the planet, allowing glaciers to grow even larger. As temperatures plunge, the entire planet is encased in ice. This persists until carbon dioxide from volcanic eruptions builds up in the atmosphere and gradually brings Earth's temperatures back to the melting point of ice. Once ocean water is exposed at the equator, the planet rapidly transitions into a hot phase. The temperature later returns to its starting point after enough carbon dioxide has been scrubbed from the atmosphere through the formation of carbonate minerals.
Global average
surface temperature
(celsius)
How the Earth may have looked
-40
40°C
-20
0
20
Elapsed time since onset of snowball Earth (millions of years)
0
1
2
3
4
5
6
MURAT YÜKSELIR / THE GLOBE AND MAIL,
SOURCE: TERRA NOVA
The making and unmaking of snowball Earth
In a snowball Earth scenario, the growth of glaciers at the poles increases the amount of sunlight that is reflected into space. This cools the planet, allowing glaciers to grow even larger. As temperatures plunge, the entire planet is encased in ice. This persists until carbon dioxide from volcanic eruptions builds up in the atmosphere and gradually brings Earth's temperatures back to the melting point of ice. Once ocean water is exposed at the equator, the planet rapidly transitions into a hot phase. The temperature later returns to its starting point after enough carbon dioxide has been scrubbed from the atmosphere through the formation of carbonate minerals.
How the Earth may have looked
50°C
40
30
Global mean surface
temperature (celsius)
20
10
0
-10
-20
-30
-40
-50
0
1
2
3
4
5
6
Elapsed time since onset of snowball Earth (millions of years)
MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: TERRA NOVA
“There was a very long period of time when I would ask myself every day, many times a day, if this could possibly be true,” he said. What kept him on track was the evidence.
Barbara Sherwood Lollar, a geochemist at the University of Toronto, said Dr. Hoffman excelled by being the kind of scientist who doesn’t abandon a puzzle when its pieces don’t fit together neatly.
“It takes a particular person, with vision, but also tenacity, to continue to work the problem,” she said. “Paul is one such person.”
Dr. Hoffman’s fascination with Earth’s past came early, starting with childhood summers spent exploring the Niagara Escarpment around Caledon, Ont. As a teenager, he joined the Toronto Field Naturalists’ Club, gravitating toward the mineral collectors “because they went on field trips.”
Dr. Hoffman looks over the Cranswick River in the Mackenzie Mountains, NWT, in 2001.Sasha Turchyn/Supplied
A key moment came after his first year at McMaster University when he was looking for a summer job and was advised to seek out James E. (Jet) Thomson, then-director of the Ontario Geological Survey.
According to Dr. Hoffman, Mr. Thomson “looked me up and down and said: ‘Have you ever been in a canoe?’ ”
What followed was a four-month stint mapping the geology in a remote corner of Northwestern Ontario. For a scientist, it was an invaluable practical experience.
“It’s the act of synthesis, hypothesis and testing in real time,” Dr. Hoffman said. “You’d go to an outcrop and, based on what you found, you’d try to make a prediction of what every other outcrop in the vicinity will be according to your conception. And because you can’t see them all, you have to decide which one to go to next – which one will be the most catastrophic to your idea if it isn’t what you predict.”
Dr. Hoffman’s early career coincided with the development of plate tectonics, a paradigm shift in the field. By the late 1960s, scientists realized that the continents were moving and that Earth’s crust was subdivided into large sections, called plates, that could pull apart or collide. Dr. Hoffman, who earned his PhD in 1970, went to work for the Geological Survey of Canada, where he made his reputation deducing how the Canadian Shield was built up from crustal fragments that existed long before today’s continents were on the map.
In contrast, the ice ages that gave Canada many of its familiar geographic features, including the Great Lakes, came much later – only millions of years ago. But deeper in the rock record were signs of earlier periods of glaciation.
By the 1980s, signs were turning up that there had once been glaciers at the equator hundreds of millions of years ago. Joseph Kirschvink, a geologist at the California Institute of Technology, was among those who pondered this. He knew there was a potential feedback loop in which a cooling climate caused ice caps near the poles to grow larger and reflect more sunlight into space, making the planet still colder until the oceans and continents were entirely frozen over.
It was Dr. Kirschvink who first saw there was a way out of this scenario: Over time, carbon dioxide from volcanic eruptions would build up in the atmosphere until Earth warmed up again and the ice retreated. In 1992, he included the idea in a chapter he contributed to an academic publication and dubbed it “snowball Earth.”
It was on a trip to Namibia that Dr. Hoffman found evidence to support the snowball Earth hypothesis and that is may have occurred at two separate times, between 720 million to 630 million years ago.Chad Hipolito/The Globe and Mail
It was that same year that Dr. Hoffman, frustrated by a lack of research funding, left Canada for Harvard University. There, his work on ancient continents led him to explore Namibia, where he could access rocks from a period he was most interested in. And it was in Namibia that he would find compelling evidence for a snowball Earth – now thought to have occurred at two separate times, between 720 million to 630 million years ago.
Though snowball Earth was regarded as a fringe idea at the time, Dr. Hoffman pursued it. To fully understand how it worked he had to go beyond his own geological training and dig into physics and climatology, showing what may have taken place and how it matched the available data.
“Whenever I don’t understand something, my first instinct is to take two steps backwards not two steps forward,” Dr. Hoffman said.
Working with Dan Schrag, a Harvard colleague, Dr. Hoffman was able to build a strong case for snowball Earth, which came together in a landmark 1998 paper in the journal Science.
It was a turning point, said Galen Halverson, a professor at McGill University who was then Dr. Hoffman’s PhD student and a co-author on the paper.
“I was not prepared for how big of a deal it was,” Dr. Halverson said. “Every Earth science conference after that had to have a session on snowball.”
The was also plenty of pushback from colleagues, but as time passed, evidence for snowball Earth has continued to mount.
Dr. Hoffman, now an adjunct professor at the University of Victoria, said that his main task these days is finishing a book that provides a full scientific overview of snowball Earth and its implications, particularly for life. The microscopic precursors of today’s multicellular lifeforms would have been hard pressed to survive on a planet covered by ice, he said. And that pressure should have left a genetic trace.
“I want to take that to the biologists because I think the best test of the scenario is going to come from the genomics of modern organisms.”