When a scientist wins a Nobel Prize, the King of Sweden hands that person a golden megaphone. It’s not the loudest instrument of its kind, but it has a bright, luxuriant finish, and it is guaranteed to work for the lifetime of its owner.

That is how it came to pass that on July 1st, as temperatures in Paris reached a record 103.5 degrees F, as the London underground became hotter than the legal limit for transporting cattle, a Nobel laureate named Ivar Giaever (Physics, 1973) stood at a dais in Lindau, Germany, and argued that climate change wasn’t happening. Or maybe he argued that climate change is happening, but that’s a good thing—it was hard to tell. He showed a series of slides containing dubious data of unclear origin and said things like: “The temperature has not increased!” And then: “Global warming is supposed to cause climate change. But the climate changes anyway!” And: “Another thing which amazes me really is when they talk about climate change it’s always to the worse. You see, the climate changes also for the better. And if the climate changes you have a 50 percent chance anyway it’s gotta be better someplace, for heaven’s sake.”

The occasion was the 65th Lindau Nobel Laureates Meeting, an annual gathering on the Swabian shores of Lake Constance where old dons give talks and mingle with young scientists from around the world. People were whispering about Giaever’s scheduled talk from the start. Monday afternoon one of the laureates, an astrophysicist, mentioned it to me with a weary roll of the eyes. We were standing in an interview room at the main conference hall. It contained one of the approximately three air conditioners in the entire nation of Germany. He said that a few of the Nobelists had actually discussed issuing a statement on climate change from the meeting. The idea was to support the science behind anthropogenic warming ahead of December’s climate meetings in Paris, where the nations of the world will—once again—try to reach a deal to reduce greenhouse gas emissions. But it was hard not to see such a declaration as a unison megaphone blast intended to drown out Giaever’s.

That day, the weather was perfect—cobalt sky, steady lake breeze—but the heat came quickly, and by Wednesday the air was a lead blanket. Walking through Lindau’s medieval streets it was easy to imagine that this was what first-world summers would be like from now on: heat inescapable, air-conditioning largely nonexistent, water rationed out in disappointingly small, ice-free portions. Even the impressive recycling efforts of the conference organizers took on extra layers of meaning. Those neat racks of empty water bottles stacked throughout the conference hall started to look like crates of fine china—indulgences of an era when people still drank water out of bottles made from petrochemicals.

By Thursday, Lindau’s old buildings had had some time to absorb the heat, and it was hotter indoors than out. That morning five of the laureates gave a press conference on the second floor auditorium of Forum am See, a whitewashed embassy-like hall facing the lake. The windows were open, and a breeze kept the room tolerable. Brian Schmidt (Physics, 2011), Steven Chu (Physics, 1997), David Gross (Physics, 2004), George Smoot (Physics, 2004), and Peter C. Doherty (Physiology or Medicine, 1996) sat on a low riser while a couple dozen journalists asked questions. Robert Wilson (Physics, 1978), co-discoverer of the cosmic microwave background, sat in the front row of the audience.

Schmidt began by explaining the precedent for this declaration. “We find ourselves 60 years after the declaration at Mainau about nuclear war,” he said. “This year the laureates here, represented in part by those on the stage, are going to make a declaration this year discussing the threat of climate change.”

Schmidt was referring to the 1955 Mainau Declaration, initiated at this same conference by Germany physicists Otto Hahn and Max Born. “We, the undersigned, are scientists of different countries, different creeds, different political persuasions,” it began. “Outwardly, we are bound together only by the Nobel Prize, which we have been favored to receive. With pleasure we have devoted our lives to the service of science.” And then things get heavy. “By total military use of weapons feasible today, the earth can be contaminated with radioactivity to such an extent that whole peoples can be annihilated,” the declaration continued. Interestingly, it does not end with a call for nations to renounce nuclear weapons—it instead asks nations to “refrain from violence as the last means of politics” altogether, for in this new world, any traditional skirmish could go nuclear.

The 2015 declaration was still being drafted, the panelists said. They weren’t sure how many Nobelists would sign it, because it was tough to get everyone coordinated via email, especially with Internet access being weirdly spotty in the conference hall. All agreed that the goal was to support the IPCC and exercise whatever influence they could on the upcoming COP meeting in Paris.

Each scientist had a personal reason for concern. David Gross had just returned from Kashmir, where it was much hotter than normal, and the people were trying to figure out how to cope with rising temperatures and a looming permanent shortage of meltwater from the surrounding mountains. George Smoot lived for many years in California, and he saw the drought there as a consequence of climate change. Peter Doherty, approaching the problem as a physician, was alarmed by a Lancet Commission on Health and Climate Change report. “Even on a moderate scenario we may expect to see the progressive breakdown of civil society across the planet by 2100,” he told the reporters in the audience. Steven Chu said he thought of action on climate change as an inexpensive insurance policy, a media-friendly answer clearly honed by his time in Washington.

“I want to stress that this is a critical year,” said Gross. “Another failure like in Copenhagen or in Rio would be incredibly demoralizing. And it might very well force sovereign countries to take action on their own. There are ways of mitigating the disasters—fight over water resources, manipulate rainfall, geoengineer. I’m convinced after this week in the Himalayas that the countries that depend on those water resources are not going to stand still as their rivers are destroyed.”

Asked about Giaever, Brian Schmidt was diplomatic. “Science is made up of distinct individuals and diversity of opinion,” he said. “We will acknowledge that one of our laureates has a counterview. A single Nobel laureate who disagrees with the consensus does not eliminate the consensus.”

Peter Doherty wasn’t having it. He leaned forward in his chair and explained the process that creates people like Ivan Giaever. “You’re an eminent, long-retired scientist, and you take a controversial opinion because otherwise you’d be ignored.” he said. “It’s very common.”  

“But I want to make it clear that we are respectful of views,” Schmidt said.

“Some of us are,” Doherty shot back.

The next, sweltering morning, the laureates, young scientists, and various other conference-goers boarded a spaceship-looking boat and sailed for Mainau, a sort of botanic-garden island in the middle of Lake Constance. A few hours later, the attendees were gathered on a lawn under a white wedding-reception tent, ready to watch the Nobelists sign their statement. A little before 1 pm, after a quick introduction by Countess Bettina Bernadotte af Wisborg, President of the Council for the Lindau Nobel Laureate Meetings, Brian Schmidt, gamely wearing a black sport coat, took the stage.

He kept it short, quickly getting to the meat of the declaration: “We believe that the nations of the world must take the opportunity at the United Nations climate change conference in Paris in 2015 to take decisive action to limit future global emissions.” With that, 36 Nobelists, almost all in short sleeves, filed forward and signed one of several sheets of letterhead lying next to the text of the declaration itself.

It’s safe to assume the signatories had realistic expectations for what this piece of paper would accomplish. At least some of the scientists who signed the 1955 Mainau Declaration on nuclear war did. In her book Heisenberg in the Atomic Age: Science and the Public Sphere Cathryn Carson quotes Werner Heisenberg, a signatory to the declaration, saying, in hindsight: “Every human being in his right mind is for peace and against the atomic bomb and doesn’t need statements by scientists.”

Still, the day before, back at the press conference, David Gross argued that scientists—if not the Mainau Declaration itself—did help make the public aware of the dangers of nuclear weapons, an awareness that, for example, eventually put an end to atmospheric testing of nukes. “After the war,” he said, “the scientific community that had built the bomb felt a responsibility to warn about bomb. As I look back in history people were not aware of the dangers. They were aware of the power, but not radiation, etc.” Not that the threat of nuclear annihilation has entirely gone away, he admitted. But things did cool off. And this, he argued, is a similar catastrophe. The declaration “probably will have a very small effect,” he said, “but there is one other aspect of this which is very important: Here at this meeting we are talking not just to ourselves but to 600 young scientists around the world. It’s important that we serve as role models to remind them you’re young scientists you’re going to suffer from this problem more than we are.”

Peter Doherty was clear-eyed about the influence he wielded back in Australia. “In my country the visibility of a Nobel prize winner is something like a minor figure in a coffee commercial that hasn’t run for five years.” But he was still sitting on that stage, probably because of similar reasons that Brian Schmidt gave: “I personally feel a moral bound duty to speak out,” he said. “We do have a voice that has been give to us by the honor of that award. Whether world leaders listen to us or not is up to them, but we are honor bound to speak out.”

If you have a golden megaphone, in other words, you feel a great responsibility to use it.