Climate scientist James Hansen has perhaps just published his magnum opus, his ultimate cri de coeur, and it boils down to this: world governments have set an insufficient target—by half—for staving off the worst impacts of global warming, with deadly consequences for human civilization.
Four years ago the journalist Elizabeth Kolbert, a frequent contributor to this magazine, profiled Hansen for the New Yorker. In the 1980s, Hansen was among the first scientists to warn that the earth was warming because of the buildup of carbon dioxide in the atmosphere due to the burning of fossil fuels. By 2009, Hansen told Kolbert, the latest climate science had convinced him that the threat was far greater than he had ever anticipated, and that CO2 had already reached dangerous levels. Immediate action needed to be taken, Hansen said—action that should include the shutdown of all the world’s coal plants within the next two decades. The same week that Kolbert’s profile was published, Hansen was arrested for protesting at a West Virginia coal plant.
Around the same time, Hansen recruited 17 colleagues—climate scientists, paleobotanists, ocean current experts, global economists—to collaborate on a research paper, published today, that makes a similarly impassioned argument about the dire need to address climate change. Allowing a global temperature rise of 2 degrees Celsius—the international goal adopted at a 2009 United Nations-sponsored conference—“would lead to disastrous consequences,” the paper argues, including sea-level rise on the order of at least 20 feet, which would inundate most coastal cities. Even 1 degree Celsius over pre-industrial levels, which we’ve come close to reaching already, is going to be rough for humanity—indeed, all life—leading to long droughts, drinking water shortages, more intense wildfires, ocean acidification, mega heatwaves, and worldwide extinctions of plant and animal species.
The policy prescriptions from Hansen and his co-authors are not all that radical: they advocate for the adoption of a carbon tax by some of the world’s largest economies—particularly the United States and China—along with an immediate shift to low-carbon energy sources such as wind, solar, and nuclear power. But whether the change to clean energy sources can—and will—be made in the timeframe and at the scale Hansen and his colleagues advocate continues to be the big question.
"Without much stronger policies, we will not only blow by the one-degree limit urged by Hansen, but the two-degree limit embraced by governments around the world," said Dan Lashof, director of the climate and clean air program at NRDC, which publishes OnEarth.
Although 1 or 2 degrees doesn’t sound like much, the planet’s history shows that life on earth is actually very sensitive to small temperature changes.
Hansen insisted that change can happen rapidly when the world sees the need for urgent action. “In World War II, we produced a lot of ships and planes very quickly,” he told a small group of journalists in New York at Columbia University, where he is now director of the Earth Institute’s new Program on Climate Science, Awareness, and Solutions after retiring earlier this year as director of NASA’s Goddard Institute for Space Studies. It was a mostly friendly room—reporters who cover the environment and climate change on a regular basis—but Hansen and the institute’s director, economist Jeffrey Sachs (also a co-author of the paper), couldn’t escape skepticism about whether their proposed solutions were politically feasible. New York Times blogger Andrew Revkin, in particular, pressed them on the tough political realities facing significant action on climate change.
“Don’t say it’s not going to happen,” Sachs pleaded at one point. “Focus on what can happen. ... This paper makes it extremely clear what the costs of the current trajectory are. We’re soon to breach all known historical bounds. We don’t want that kind of world.”
Indeed, what’s different about Hansen’s latest effort—for a scientific paper, at least—is the stark moral and ethical terms in which the authors present their findings, painting a picture of humanity at a crossroads, forced to choose between dooming future generations by continuing to burn fossil fuels, or giving them a fighting chance by turning to other energy sources just in the nick of time. Making the moral case for holding global warming closer to 1 degree Celsius caused a problem with the editors at one scientific journal, Hansen said—they kept trying to edit it out and stick to the physical science—so he and his colleagues withdrew the paper and published it instead at PLoS ONE, an open-access peer-reviewed journal from the Public Library of Science.
The researchers base their scientific conclusions on studies of the planet’s geological history. “The modern world as we know it,” Hansen and his colleagues assert, is adapted to climate conditions that have existed for the last 10,000 years, since the end of the last Ice Age, when agriculture and human cities began to arise. Throughout that period, temperatures haven’t varied beyond 1 degree Celsius. So we’re nearly outside of the range that any of our human ancestors experienced already. And although 1 or 2 degrees doesn’t sound like much, the planet’s history—not to mention current conditions—shows that life on earth is actually very sensitive to small temperature changes.
Hansen and other climate scientists have been warning in stronger and stronger terms over the last decade that humanity is nearing a point of no return, “baking in” so much change—due to CO2 already in the atmosphere from burning fossil fuels—that centuries of warming and the resulting consequences are inevitable. “If we have any love for our children or grandchildren,” Hansen said today, “we can’t accept that.”
That plea on behalf of future generations is in keeping with Hansen’s ever-more aggressive efforts to sway public opinion and change political policy on climate, from his civil disobedience at coal plants and the White House to writing the 2009 book Storms of My Grandchildren. Now he’s trying legal action—“I could not sue the government as a government employee,” he said of his decision to leave NASA—and hopes this latest paper can be used to help bolster future lawsuits against state and federal governments “for not doing their job protecting the rights of young people and future generations.”
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