AMHERST -- Thirty-five years ago Raymond Bradley spent a miserable summer in the Canadian Arctic.
There to map glaciers, he was cold and wet. He was cramped sharing a pup tent with a fellow graduate student. The food, freeze-dried pellets of meat and vegetables, was terrible.
After Bradley returned to the University of Colorado, where he was working on a doctorate in geography, his memory shifted. ''The magic of the Arctic," he says, ''cast its spell."
From that shaky start, Bradley, now a professor of geosciences at the University of Massachusetts and director of its Climate System Research Center, became an internationally recognized paleoclimatologist known for drilling into the sediment beds of frozen Arctic lakes to find in their layers evidence of centuries of climate change. He coauthored studies that -- using data from glaciers, tree rings, coral, and historical records -- found the late 20th century to be the warmest period in 1,000 years. This research produced the ''hockey stick" graph that's become widely used to reflect global warming.
He's also one of three scientists in a political maelstrom. Representative Joe Barton, the Texas Republican who chairs the House energy committee, asked the coauthors of the 1998-99 ''hockey stick" studies for a detailed accounting of the data and funding of all their research on climate change. That prompted protests last month not only from the American Association for the Advancement of Science, the National Academy of Sciences, and individual scientists, but also from Republican Sherwood Boehlert of New York, chairman of the House science committee, and Democrat Henry Waxman of California, a member of the energy committee.
In a letter, Boehlert blasted an investigation whose ''purpose seems to be to intimidate scientists rather than to learn from them." Meanwhile, energy committee spokesman Larry Neal defends the inquiry. ''We have been hotly advised by critics to shut up and just keep the money coming," Neal says via e-mail. ''Representative Barton believes that public money for public science doesn't fall down like manna from heaven."
For Bradley, 57, who as a boy in Merseyside, England, built weather stations at school, this is the latest twist in an increasingly politicized career that began as an esoteric exploration of natural climate variation.
He and three graduate students spent 2 1/2 weeks in the Canadian Arctic in late spring, drilling through 6 feet of ice, 300 feet of water, and almost 40 feet of lake bed to extract sediment from Murray Lake on Ellesmere Island. Afterward, while he and his wife hiked the Pyrenees of France and Spain, Barton's request arrived at UMass. Bradley's short, three-page response reviews research on climate change and directs the committee to his resume, papers, and data archives.
''You can't be pushed around for partisan political reasons," Bradley says. ''Any scientist should be concerned about this. Today it's global warming. Tomorrow it will be stem cell research or evolution or God knows what."
'The Indiana Jones stuff'
Only in the late 1990s did Bradley, author of a textbook on paleoclimatology, become convinced human activity was heating the planet. ''I wasn't an evangelist for global warming until quite recently," he says.
Most climate scientists now believe, as stated by the Intergovernmental Panel on Climate Change, that natural forces alone cannot explain the recent rise in greenhouse gases and temperature. Some skeptics, as Barton emphasizes, question the methodology Bradley, Michael Mann of Pennsylvania State University, and Malcolm Hughes of the University of Arizona used in their ''hockey stick" studies. Those studies, say Bradley and others, are buttressed by others that, whether replicating or tweaking their original assumptions or using different approaches, reach the same conclusion.
''The notion that human beings are influencing the earth's climate is known from a whole variety of sources. The hockey stick is a visually engaging tool to show that," says Michael Oppenheimer, professor of geosciences at Princeton. ''Bradley," he adds, ''is the guy with the most scientific heft in the group, and he has not played in the political arena. They're all good scientists."
Bradley seeks science in earth's most forbidding places. ''The Indiana Jones stuff," quips his colleague Hughes. The adventurous young graduate student is now the adventurous, white-haired, white-bearded, bespectacled professor who regularly leads expeditions to the northern Arctic. The tents are bigger, the food -- frozen steaks and chops and chocolate treats for difficult days -- considerably better, but he's still arriving in twin-engine planes outfitted with skis to land on frozen lakes. He always sleeps with a shotgun in his tent -- and travels with a shotgun in his snowmobile -- in case he meets a polar bear.
''These," Bradley says, ''are the experiences that shape you."
His career parallels the development of a discipline that was in its infancy when he was a graduate student and scientists wondered if a new Ice Age were coming. ''We stumbled along," Bradley says. ''That's the way science works. These guys in Washington seem to think it's some kind of conspiracy, that we start out with an agenda and then we conduct the science to prove that."
Bradley is drawn to the Arctic's stark beauty, the jagged mountains of Baffin Island, site of his first trip, the way the perpetual daylight of an Arctic summer produces ''reds and oranges and blues and deep shadows." On Ellesmere, to which he keeps returning, the landscape is softer. ''It has much more wildlife," he says, ''including caribou and musk oxen. Arctic hare, big rabbits, foxes, wolves. A lot of birds. Snow geese. Snow buntings. Jaegers. Seals on ice."
In China he's studied fields of glacial silt. ''We went to villages," he says, ''that had never seen a white person before." On the northern ice field of Tanzania's Mount Kilimanjaro he's established a weather station at 19,000 feet above sea level. In the thin air, Bradley suffered excruciating headaches.
''The sun goes down at 6. By 7 o'clock it is freezing. It is absolutely bitter cold, much colder than the Arctic in summer," Bradley says. ''It's dark for 12 hours. Because you're at high elevations, you're lying in your sleeping bag and your heart is racing. Every now and again you doze off. All of a sudden you wake up because you're not getting enough oxygen. You find yourself, even though you're tired, lying there listening to your heart beat and waiting for the sun to come up."
The samples his teams collect contain clues to climate past: A thick layer in lake sediment, for instance, indicates a warmer summer and more silt flow. In the arduous work of digging holes and hauling up cylinders of sediment and in the tasks of everyday life in the wilderness, camaraderie develops and Bradley relaxes. ''You see the professorial side here. There you see a more loose, more fun side," says graduate student Ted Lewis.
Bradley has had close calls. Once, a plane lost an engine on takeoff just after dropping off his party. It managed to land again. ''If that had happened when we were fully loaded with our equipment," Bradley says, ''that would have been the end."
Once, as he and a colleague wandered lost and disoriented on a snowmobile in a whiteout for an hour, seeking the cabin where they'd spend the night, they knew from the fresh tracks beside them that a polar bear was near. ''If the sea ice goes out and the polar bears get left behind on the land, they're very hungry and they're very aggressive," Bradley says. ''We could have come on top of that bear without realizing it."
He's fascinated with the history of Arctic exploration and collects rare books on the subject. In 1971, on his first trip to Ellesmere, he sledded 20 miles to the site where Adolphus Greely's ill-fated 1881-84 expedition lived for two winters before setting out by boat to meet the ship that never came for them. Only six of two dozen men survived that third winter. In a parka in a tent in the Arctic, Bradley has read aloud from Greely's memoirs. ''There's some of that old-style British explorer in him," graduate student Carsten Braun says of Bradley.
In Amherst the walls of the Climate System Research Center are decorated with photos from expeditions and with graphs, one of the hockey stick and another mapping 400,000 years of gas bubbles trapped in an Antarctic ice sheet that shows a jump in carbon dioxide and methane in the past 150 years.
Since he has become convinced of the human hand on the global thermometer, Bradley turns off lights in vacant classrooms. He drives a 1992 Volvo that gets 28 miles per gallon. He gives briefings about global warming. He wishes Congress had encouraged conservation in its energy bill and that consumers would demand fuel efficiency from automakers. He wonders what will happen next in the investigation that has distracted him from his work.
''I also worry about the students," Bradley says. ''If I saw this happening to my adviser, would I want to go through this? They may decide they don't want to speak out. They may hedge what they saw."
On July 27, a month after Barton launched his probe and two weeks after Bradley responded, the professor became a US citizen. In a ceremony at the Hynes Convention Center, Bradley and 2,521 others swore ''true faith and allegiance" to the Constitution.
''It's a very important thing to be a citizen of the United States," Bradley says. ''Obviously it wasn't the most ideal time to do it."