NASA Jet Propulsion Laboratory
One of the great things about the giant American Geophysical Union yearly meeting in San Francisco is the tremendous diversity of subjects that you can plunge into. I started the conference in a session devoted to the history of geophysics. One paper examined the contribution of Scots to the discovery of the existence of the ice ages in the early 19th century, while another unearthed James Van Allen's role in the Argus series of nuclear weapons tests that were designed to “ring the magnetosphere's bell” during the late 1950s and early 1960s. I also attended a pair of sessions devoted to ice loss from marine glaciers in Greenland and West Antarctica. Scientists from a wide variety of U.S. and foreign institutions spoke about their efforts to understand the mechanisms behind the widely-reported phenomenon. At a very general level, they agree that changes in the oceans surrounding these glaciers and their ice shelves are responsible for eroding the ice. But they don’t know whether the cause is warmer water (and the ocean around both Greenland and West Antarctica has warmed significantly), faster circulation of water at the glacier margins (evidence for this seemed mixed), or some combination of both.
To try to understand how marine glaciers erode, the researchers have deployed a variety of tools: moored buoys, ship-based hydrographic cruises, various satellite and aircraft-based remote sensors, and numerical models. One research group at the University of Chicago has even studied the process of ice shelf disintegration using plastic models (no, not rubber ducks!) in a big water tank. The speaker drew a big laugh from the audience, but he had a point: we never catch an ice shelf breakup "in the act" early enough to provide a complete time series to study. We can only study the process through modeling, and geoscientists have used simplified models to help understand complicated phenomena for a couple of centuries. And a physical model like a water tank simply contains different simplifications than numerical models.
The last session I attended before hunger pangs set in was on the co-evolution of planetary atmospheres and climates — in this case, Mars and the Saturnian moon Titan. These researchers are trying to understand the evolution of greenhouse gas inventories over the past four billion years with far less evidence than is available to Earth scientists — bits of evidence like the escape rates of hydrogen and carbon dioxide into space and their present surface compositions.
Erik is a historian based at NASA's Jet Propulsion Laboratory in Pasadena, California.
Global warming is not new.
You might think from the amount of “climate science debate” that is given airtime in the U.S. media that it’s undiscovered territory. But it’s not. The science is very well established and goes back a long way. Global warming is not a new concept.
The Victorians knew about it. John Tyndall (born 1820) knew about it. So did Svante August Arrhenius. In April 1896, Arrhenius published a paper in the London, Edinburgh and Dublin Philosophical Magazine and Journal of Science entitled “On the influence of carbonic acid in the air upon the temperature of the ground.” (Arrhenius referred to carbon dioxide as “carbonic acid” in accordance with the convention of the time.)
Arrhenius’ paper was the first to quantify how carbon dioxide contributed to the greenhouse effect — carbon dioxide warms up the Earth by trapping heat near the surface, a bit like swaddling the planet in an extra blanket. Arrhenius was also the first to speculate about whether changes in the amount of carbon dioxide in the atmosphere have contributed to long-term variations in Earth’s climate. He later made the link between burning fossil fuels and global warming.
Another person who “knew” some time ago was Frank Capra. Graduating from Caltech in 1918, he went on to become a famous filmmaker responsible for “It’s a Wonderful Life” and other movies. But one that stands out, at least for nerds like me or people with an interest in climate change is “Meteora: The Unchained Goddess”, released in 1958:
Made for Bell Labs, this most awesome educational film speaks of “extremely dangerous questions”:
Dr. Frank C. Baxter: “Because with our present knowledge we have no idea what would happen. Even now, man may be unwittingly changing the world’s climate through the waste products of his civilization. Due to our release through factories and automobiles every year of more than six billion tons of carbon dioxide, which helps air absorb heat from the sun, our atmosphere seems to be getting warmer."
Richard Carlson: "This is bad?"
Dr. Frank C. Baxter: "Well, it's been calculated a few degrees rise in the Earth’s temperature would melt the polar ice caps. And if this happens, an inland sea would fill a good portion of the Mississippi valley. Tourists in glass bottom boats would be viewing the drowned towers of Miami through 150 feet of tropical water. For in weather, we’re not only dealing with forces of a far greater variety than even the atomic physicist encounters, but with life itself." In 1958, they knew about the effects of heating up the planet. In the 1800s they knew about it. Today, the biggest challenge facing climate scientists lies in predicting how much our climate will change in the future. It’s not a trivial task, given how complicated the climate system is — we can barely predict in detail more than a week’s worth of weather. We’re not viewing Miami through bottomed-glass boats yet, but we’re already beginning to see some of the predictions of global warming — melting sea and land ice, sea level rise, more extreme weather events, changes in rainfall and effects on plants and animals — be borne out.