Can you believe, he said to me in one of our conversations, that some of us get to spend our lives exploring places like Greenland and Antarctica?  Many climate scientists spend most of their days behind a desk. Vast troves of data arrive from satellites orbiting the planet or from robotic floats roaming the ocean, and the task is to plug the numbers into computer models.  That work does have its hazards. Publish elementary facts about melting ice and rising seas, and you may be attacked by name on the floor of Congress. Speak out about the risks of unchecked fossil-fuel emissions, and people you have never met will email you death threats.  Yet for a whole cadre of climate scientists, the work entails real physical risks. Thousands of specialists — glaciologists, geologists, geodetic engineers, wildlife biologists and many others — must travel to remote regions to better understand the effects of warming on the natural world.  Experts who retrieve long cylinders of glacial ice to recreate climates of the past are rushing to secure samples before the ice melts and the precious information it records is gone forever. The immense ice sheets covering Greenland and Antarctica, whose disintegration would raise the ocean and drown coastal cities the world over, must be studied firsthand if scientists hope to understand what is happening to them.  Over meals, after a couple of beers, many of these scientists will speak of close calls on their expeditions: the slip of a foot on a narrow mountain trail, the collapse of a heavy piece of gear inches from somebody’s head, the icy crevasse spotted just in time. For his Greenland expeditions, Dr. Hamilton carried a rifle to guard against attacks by polar bears.  Lonnie G. Thompson, a renowned glaciologist at Ohio State University, was once camped on an ice cap when a savage wind knocked down his tent and began blowing it off the side of the mountain — with him inside. A colleague helped him stop the slide by plunging an ax through the canvas into the ice.  I have watched on expeditions as senior scientists have put their own bodies at risk to protect junior associates and students. Nor are students who go on these trips immune to danger. One of the tragedies of Dr. Thompson’s career was losing a graduate student, Shawn Wight, to an illness that began with altitude sickness on a Himalayan expedition.  You might imagine that a certain kind of personality would be drawn to this work, a swashbuckling Indiana Jones type for whom science is an excuse to go off and have grand adventures.  The reality, though, is that most field scientists are rational people, not thrill-seekers. Even out on the ice, they spend a lot of their time thinking in equations. They tend to be safety minded and careful, following rules as best they can.  The real thrill for them is figuring out something hard — becoming the first human being to understand why that particular glacier has sped up so much, or what role the warming ocean might be playing in destabilizing the world’s ice sheets.  Over a weeklong trip to the east coast of Greenland in 2010, I spent hours talking to Dr. Hamilton and several of his colleagues. He was deeply worried, and in that beautiful and savage landscape, it was easy to see why. A helicopter deposited our team at the edge of the immense Helheim glacier, which carries ice from the Greenland sheet and dumps it into the sea, raising the sea level.  The moment we landed, Dr. Hamilton pointed out a sort of bathtub ring on the rock walls of the canyon. As climate change had apparently caused the glacier to speed up, the surface had dropped some 300 feet, exposing light-colored rock that had not seen the sun in thousands of years.  The exact mechanics of what was happening were far from clear. With several colleagues, including Fiamma Straneo of the Woods Hole Oceanographic Institution, Dr. Hamilton was struggling to work that out.  The issue can be overwhelming. The science is complicated. We get it. This is your cheat sheet.  After taking the doors off the chopper, they braved icy wind to hover over the fjord at the mouth of the glacier. They dropped instruments to measure water temperatures below the surface that were high enough to weaken the ice from below, possibly a consequence of the overall warming of the global ocean.  As we talked through the complexities of the science, it dawned on me that the work Dr. Hamilton and his colleagues were doing was really a race against time. The planet was, and is, changing faster than the scientists can understand it.  “We’re always playing catch-up,” Dr. Hamilton said in Greenland. “The ice sheet does something we never predicted, and then we see it. It makes you think there’s just so much we don’t know.”  The loss to science from Dr. Hamilton’s death will be immense. In a phone conversation on Monday, Dr. Straneo recalled how often he went out of his way to help colleagues with the difficult logistics of polar research — the maestro behind many papers on which his name never appeared. The personal loss for his family and colleagues is acute, as well, of course. He leaves a wife, Fiona, and two adult children, Martin and Calum.  At the time of that Greenland trip, six years ago, Dr. Hamilton was frustrated that the public was not yet sufficiently alarmed about the danger of climate change. If there is any consolation to be found in his death, it is that he lived long enough to see the world’s political leadership begin to take the problem seriously. The Paris Agreement on climate change, under which the nations of the world are pledging to cut emissions, will take effect early next month.  If the worst of the danger is ultimately averted, it will be because of the brave efforts of people like Gordon Hamilton.  An article on Tuesday about Gordon Hamilton, a climate scientist who died in Antarctica, described inaccurately an accident involving Lonnie G. Thompson, a glacier scientist. A colleague helped stop the slide of Dr. Thompson’s tent down a mountainside using an ax; Dr. Thompson did not stop the slide by himself. The article also misstated the circumstances of the death of one of Dr. Thompson’s graduate students. The student, Shawn Wight, died from a lung infection acquired after falling ill with altitude sickness on a Himalayan expedition. He did not die of altitude sickness.  A version of this article appears in print on October 25, 2016, on page D1 of the New York edition with the headline: Discovery Amid Danger. Order Reprints| Today's Paper|Subscribe
Dr. Hamilton, who was killed in Antarctica over the weekend, studied glaciers with our future in mind, and with a smile.