https://harvardmagazine.com/2020/11/features-controlling-global-thermostat
Controlling the Global Thermostat
Coming to terms with climate change’s relentless, long-term fallout
Wildfires in California are one example of climate-change damages happening now.
CLIMATE CHANGE may be the most inexorable catastrophe the human species has ever faced. What to do about the warming is dominated by uncertainties—and a pervasive inability to agree on who should do what in response. Can humanity agree to meet its energy needs with carbon-free renewables, such as wind and solar power—and if so, how quickly could the transition be made, and feasibly paid for? How high will sea level rise by 2050? By 2100? Given rich nations and poor ones, and public and political attention spans measured in a few years (if that long), rather than decades or centuries, what mechanisms exist to make collective decisions on long time scales, and to allocate the resulting pain and gains?
These are all important questions—but even they ignore a central certainty that no one appears to be addressing: what Dan Schrag calls “climate change’s dirty little secret.” “Even if we could become carbon-neutral tomorrow,” says the director of the Harvard University Center for the Environment, “the climate will keep changing for thousands of years, the ice sheets will keep melting, and the seas will continue to rise.”
The CO2 Crisis
ATMOSPHERIC CARBON DIOXIDE (CO2), the chief global-warming agent by volume, is increasing rapidly. In May 1960, the gas made up 317 parts per million (ppm) of earth’s atmosphere as measured at Mauna Loa, Hawaii, up from preindustrial levels of about 280 ppm; by this May, as humans continued to release more than 35 billion metric tons of CO2 annually, the figure had risen to 417 ppm—and during that period, average temperatures over land increased about 2.5 degrees Fahrenheit. The current, accelerating rate of CO2 increase is 2.5 ppm per year: 100 times faster than at any period in Earth’s geological history, straining the ability of ecosystems to adapt.
A thousand years from now, more than half the CO2 humanity has pumped into the atmosphere…will still be there.
CO2 is also persistent. A thousand years from now—30 human generations—more than half the heat-trapping carbon-dioxide that humanity has pumped into the atmosphere since the beginning of the Industrial Revolution will still be there. Twenty thousand years from now, says Schrag, a third of that CO2 willremain. As the gas traps heat arriving from the sun, temperatures will continue to increase progressively above the natural, preindustrial levels which the human species has come to expect. Unless the process can be reversed—not just slowed—the globally transformative effects of human-induced warming will thus extend across a geological time scale that has come to be known among scientists as the anthropocene: the era of extinctions in which human action plays the determining role.
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DAN SCHRAG, who is teaching the first University-wide course on climate change this fall, says it shouldn’t be “only national labs or the military” that study solar aerosol geoengineering. “We should have the best climate scientists in the world thinking about it—including all the ways that it could go wrong.” It might stabilize the Greenland ice sheet, he points out, but fail to avert a potential collapse of the West Antarctic ice sheet, whose stability depends on the temperature of ocean currents that can melt ice shelves and submarine portions of glaciers from below.
Schrag says his view of geoengineering is a little like Churchill’s assessment of democracy: that it is “‘the worst form of Government except for all those other forms….’ Taking control of the planet’s thermostat is a terrifying idea. I just think that a lot of people don’t understand that climate change is even more terrifying.”
Jonathan Shaw ’89 is managing editor of this magazine.
