Saving the Earth From Roasting
By MALCOLM W. BROWNE
Published: June 5, 1992
Is there yet time to save Earth from a catastrophic roasting that some experts now regard as virtually inevitable? A new show at the American Museum of Natural History offers a rare opportunity for visitors to crystallize their thinking about this monstrous prospect.
The museum and its partner in the project, the Environmental Defense Fund, recently opened a spectacular exhibition aimed not only at demonstrating the possibly imminent danger of global warming, but also at suggesting the possibility of salvation, provided that people everywhere begin pitching in.
The show, "Global Warming: Understanding the Forecast," occupies a substantial part of the museum's third floor and cost $3.7 million, making it one of the most expensive and elaborate temporary exhibitions the institution has mounted. It also breaks new ground.
"By attempting to look into the future, this exhibition is clearly different from anything we've done in the past," said Dr. George D. Langdon Jr., the museum's president. "We're not an advocacy organization, but our department heads agree that it's important for people to understand the scientific questions involved in the threat of global warming. We also believe that steps should be taken before it's too late." A World Debate
National leaders are meeting in Rio de Janeiro this week to consider environmental issues, and although many agree that urgent action is needed to head off global warming, President Bush, a participant in the meeting, does not. Mr. Bush's Administration contends that international regulations limiting the amount of carbon dioxide industries may emit would be enormously costly and not justified by the meager evidence that the world has already begun to warm up.
While rancorous debate among experts has not resolved this question, no one disputes the fact that carbon dioxide levels have been rising rapidly in this century and that at least in theory, their continued increase could cause global warming of up to 8 degrees in the 21st century.
The effects of the carbon dioxide may be offset, of course, by increased cloud cover reflecting sunlight away from Earth or by increased levels of sulfur dioxide produced by volcanoes (which increases cloud cover), or by many other mechanisms scientists have hypothesized -- none of them well understood.
But in some worst-case predictions, global warming could rapidly melt polar ice, raising sea levels and inundating Bangladesh, Venice and countless other places. The world's great granaries -- America's Midwest, Ukraine, Argentina and other regions -- might become arid semi-desert land, with incalculable effects on global food supplies.
A strength of the new exhibition is its wealth of displays clearly explaining some of the scientific methods and gadgets used to study Earth's climate. With money from Shearson Lehman Brothers, the National Science Foundation, the MacArthur Foundation, the Geraldine R. Dodge Foundation and Turner Broadcasting Systems, the project was able to splurge on unusually elaborate displays.
For example, scientists seeking to calculate how carbon dioxide levels in the atmosphere may have raised or lowered global temperatures in the past base some of their calculations on the study of ice buried deep in the Greenland and Antarctic ice caps. Ice core samples brought to the surface by drilling machines are windows into the past.
The age of such a sample can be determined accurately from its depth and the chemical and physical composition of its layers. Best of all, an ice-cap sample contains myriad tiny, highly compressed air bubbles trapped intact since the ice froze.
"Fossil" air in these tiny bubbles is immensely valuable to scientists. Not only does an ancient air bubble reveal how much carbon dioxide the atmosphere contained at a specific time in the past, but also oxygen isotopes trapped in the bubbles indicate the temperature of the atmosphere at that time as well. Greenland Ice and Cows
The display includes a freezer with a large window, through which viewers can look at a big chunk of real Greenland ice clouded by tiny bubbles of 660-year-old air.
Another eye-catcher is a model cow equipped with a gut represented by a twisted neon tube and a speaker emitting recorded cow burps. The point of the display is that hoofed animals digesting vegetable fodder burp enormous amounts of methane, which, with carbon dioxide, is one of the most potent "greenhouse" gases -- gases that prevent the sun's radiant energy from being reflected back into space. Cattle, mainstays of rural economies throughout the world, may be adding to the greenhouse problem.
An elderly woman said to a companion with whom she had just toured the exhibits: "This is just horrifying. I had no idea Earth was in such trouble. I'm so glad we came."
The climate debate is far from over, and to their credit, the museum and the Environmental Defense Fund offer viewers an assortment of dissenting views. Explanatory panels and interactive computer programs point out, for instance, that climate temperature varies widely and randomly, and that although the past decade has been unusually warm, the degree of warming is within the normal range of variability.
The museum and the Environmental Defense Fund might have skirted the contentious issue of birth control but chose instead to show how unchecked population growth is closely linked to carbon dioxide production and greenhouse warming. One display panel states that "to create a sustainable global society, we must both conserve our resources and stabilize population size" -- a view shared by most scientists but not by the Vatican, by many third world governments or by the Bush Administration.
"Our trustees properly insisted that we address this issue," Dr. Langdon said. "We've tried to do that without shaking our fingers at anyone."
Despite the publicity lavished on environmental problems in recent years, many people remain confused by or ignorant of the complicated facts and can benefit from guidance offered by the show, said Dr. Samuel M. Taylor, the museum's director of exhibitions.
The most common misconception, he said, is mistaking greenhouse warming (caused largely by carbon dioxide in the atmosphere) with the ozone hole (a completely different phenomenon probably caused by the release of chlorofluorocarbon compounds into the upper atmosphere).
Whether for education or the pleasure of strolling through an exceptionally well-conceived museum exhibition, "Global Warming" is worth an hour's visit. . . . Where to Learn More
The show on global warming will remain at the American Museum of Natural History, at Central Park West and 79th Street in Manhattan, through Jan. 19, after which it will tour these museums:
Los Angeles County Natural History Museum (April 3 to July 25, 1993)
Carnegie Science Center, Pittsburgh (Sept. 24, 1993, to Feb. 13, 1994)
Milwaukee Public Museum (April 15, 1994, to Sept. 5, 1994)
Denver Museum of Natural History (Nov. 4, 1994, to March 26 1995)
St. Louis Science Center (May 26, 1995, to Oct. 15, 1995)
National Museum of Natural History in Washington (Dec. 15, 1995, to May 5, 1996)
On weekdays, the exhibition is usually crowded with school groups, but museum officials say it is much quieter on Friday and Saturday evenings. On those days the museum is open from 10 A.M. until 8:45 P.M. On other days it is open from 10 A.M. until 5:45 P.M. Suggested museum admission: $5 for adults and $2.50 for children. Information: (212) 769-5100.
Photo: An Oakwood, N.J., student with a global-warming display. (Monica Almeida/The New York Times)