Billions & Billions (16 page)

Another way to check whether the climatologists know what they’re doing is to ask them to make predictions retrospectively. The Earth has gone through ice ages. There are ways of measuring how the temperature fluctuated in the past. Can they predict (or, better, postdict) the climates of the past?

Important findings on the climate history of the Earth have emerged by studying cores of ice cut and extracted from the Greenland and Antarctic ice caps. The technology for these borings comes straight from the petroleum industry; in this way, those responsible for extracting fossil fuels from the Earth have made an important contribution to clarifying the dangers of so doing. Minute physical and chemical examination of these cores reveals that the temperature of the Earth and the abundance of CO
₂
in its atmosphere go up and down together—the more CO
₂
, the warmer the Earth. The same computer models used to understand the global temperature trends of the last few decades correctly postdict ice age climate from fluctuations in greenhouse gases in earlier times. (Of course no one is saying that there were pre–ice age civilizations that drove fuel-inefficient cars and poured enormous quantities of greenhouse gases into the atmosphere. Some variation in the amount of CO
₂
happens naturally.)

In the last few hundred thousand years, the Earth has gone into and emerged out of several ice ages. Twenty thousand years
ago, the city of Chicago was under a mile of ice. Today we are between ice ages, in what’s called an interglacial interval. The typical temperature
difference
for the whole world between an ice age and an interglacial interval is only 3° to 6°C (equivalent to a temperature difference of 5° to 11°F). This should immediately set alarm bells ringing: A temperature change of only a few degrees can be serious business.

With this experience under their belts, this calibration of their abilities, climatologists can now try to predict just what the future climate of the Earth may be like if we keep on burning fossil fuels, if we continue to pour greenhouse gases into the atmosphere at a frenetic pace. Various scientific groups—modern equivalents of the Delphic Oracle—have employed computer models to calculate what the temperature increase ought to be, predicting how much the world temperature increases if, say, the amount of carbon dioxide in the atmosphere doubles, which it will (at the present rate of burning fossil fuels) by the end of the twenty-first century. The chief oracles are the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration (NOAA) at Princeton; the Goddard Institute of Space Studies of NASA in New York; the National Center for Atmospheric Research in Boulder, Colorado; the Department of Energy’s Lawrence Livermore National Laboratory in California; Oregon State University; the Hadley Center for Climate Prediction and Research in the United Kingdom; and the Max Planck Institute for Meteorology in Hamburg. They all predict that the average temperature increase will be between about 1° and 4°C. (In Fahrenheit it’s about twice that.)

This is faster than any climate change observed since the rise of civilization. At the low end, developed, industrial societies, at least, might be able with a little struggle to adjust to the changed circumstances. At the high end, the climatic map of the Earth
would be dramatically changed, and the consequences, both for rich and poor nations, might be catastrophic. Over much of the planet, we have confined forests and wildlife to isolated, noncontiguous areas. They will be unable to move as the climate changes. Species extinctions will be greatly accelerated. Major transplanting of crops and people will become necessary.

None of the groups claims that doubling the carbon dioxide content of the atmosphere will cool the Earth. None claims that it will heat the Earth by tens or hundreds of degrees. We have an opportunity denied to many ancient Greeks—we can go to a number of oracles and compare prophecies. When we do so, they all say more or less the same thing. The answers in fact are in good accord with the most ancient oracles on the subject—including the Swedish Nobel Prize—winning chemist Svante Arrhenius, who around the turn of the century made a similar prediction using, of course, much less sophisticated knowledge of the infrared absorption of carbon dioxide and the properties of the Earth’s atmosphere. The physics used by all these groups correctly predicts the present temperature of the Earth, as well as the greenhouse effects on other planets such as Venus. Of course, there may be some simple error that everyone has missed. But surely these concordant prophecies deserve to be taken very seriously.

There are other disquieting signs. Norwegian researchers report a decrease in the extent of Arctic ice cover since 1978. Enormous rifts in the Wordie Ice Sheet in Antarctica have been evident over the same period. In January 1995, a 4,200 square kilometer piece of the Larsen Ice Shelf broke away into the Antarctic Ocean. There has been a notable retreat of mountain glaciers everywhere on Earth. Extremes of weather are increasing in many parts of the world. Sea level is continuing to rise. None of these trends by itself is compelling proof that the activities
of our civilization rather than natural variability is responsible. But together, they are very worrisome.

Increasing numbers of climate experts have recently concluded that the “signature” of man-made global warming has been detected. Representatives of the 25,000 scientists of the Intergovernmental Panel on Climate Change, after an exhaustive study, concluded in 1995 that “the balance of evidence suggests there is a discernible human influence on climate.” While not yet “beyond all reasonable doubt,” says Michael MacCracken, director of the U.S. Global Change Research Program, the evidence “is becoming quite compelling.” The observed warming “is unlikely to be caused by natural variability,” says Thomas Karl of the U.S. National Climatic Data Center. “There’s a 90 to 95 percent chance that we’re not being fooled.”

In the following sketch is a very broad perspective. At the left, it’s 150,000 years ago; we have stone axes and are really pleased with ourselves for having domesticated fire. The global temperatures vary with time between deep ice ages and interglacial periods. The total amplitude of the fluctuations, from the coldest to the warmest, is about 5°C (almost 10°F). So, the curve wiggles along, and after the end of the last ice age, we have bows and arrows, domesticated animals, the origin of agriculture, sedentary life, metallic weapons, cities, police forces, taxes, exponential population growth, the Industrial Revolution, and nuclear weapons (all that last part is invented just at the extreme right of the solid curve). Then we come to the present, the end of the solid line. The dashed lines show some projections of what we’re in for because of greenhouse warming. This figure makes it quite clear that the temperatures we have now (or are shortly to have if present trends continue) are not just the warmest in the last
century
, but the warmest in the last
150,000 years
. That’s another measure of the magnitude of the global changes we humans are generating, and their unprecedented nature.

Global warming does not by itself make bad weather. But it does heighten the chances of having bad weather. Bad weather certainly does not require global warming, but all computer models show that global warming should be accompanied by significant increases in bad weather—severe drought inland, severe storm systems and flooding near the coasts, both much hotter and much colder weather locally, all driven by a relatively modest increment in the average planetary temperature. This is why extreme cold weather in, say, Detroit in January is not the telling refutation of global warming that some newspaper editorial pages pretend. Bad weather can be very expensive. To take a single example, the American insurance industry alone suffered a net loss of some $50 billion in the wake of a single hurricane (Andrew) in 1992, and that’s only a small fraction of the total 1992 losses. Natural disasters cost the United States over $100 billion a year. The world total is much larger.

Also, changes in the weather affect animals and microbes that carry disease. Recent outbreaks of cholera, malaria, yellow fever, dengue fever, and the hantavirus pulmonary syndrome are all suspected of being related to changing weather. One recent medical estimate is that the increase in the area of the Earth occupied by the tropics and subtropics, and the resulting burgeoning population of malaria-bearing mosquitos, would by the end of the next century result in 50 to 80 million additional cases of malaria each year. Unless something is done. A 1996 U.N. scientific report argues, “If adverse population health impacts are likely to result from climate change, we do not have the usual option of seeking definitive empirical evidence before acting. A wait-and-see approach would be imprudent at best and nonsensical at worst.”

The climate predicted for the next century depends on whether we put greenhouse gases into the atmosphere at the present rate, or at an accelerated rate, or at a diminished rate. The more greenhouse gases, the hotter it gets. Even assuming only moderate increases, temperatures apparently will rise significantly. But these are global averages; some places will be much colder and some much warmer. Large areas of increasing drought are predicted. In many models great food-producing areas of the world, in South and Southeast Asia, Latin America, and sub-Saharan Africa, are predicted to become hot and parched.

Some agricultural exporting nations in middle to high latitudes (the United States, Canada, Australia, for example) may actually gain at first and their exports soar. Poor nations will be most severely impacted. In the twenty-first century, in this as in many other ways, the global disparity between rich and poor may increase dramatically. Millions of people, their children starving, with very little to lose, pose a practical and serious problem for the rich—as the history of revolution teaches.

The chance of a drought-driven global agricultural crisis begins to become significant around 2050. Some scientists think that the chance of a massive worldwide agricultural failure from greenhouse warming by the year 2050 is low—perhaps only 10 percent. But of course the longer we wait, the greater the chances are. For a while some places—Canada, Siberia—might get better (if the soil is suitable for agriculture), even if the lower latitudes get worse. Wait long enough and the climate deteriorates worldwide.

As the Earth warms, sea level rises. By the end of the next century, sea level may have risen by tens of centimeters, and, just possibly, by a meter. This is partly due to the fact that seawater expands as it warms, and partly due to the melting of glacial and
polar ice. As time continues, sea level rises still more. No one knows when it will happen, but eventually many populated islands in Polynesia, Melanesia, and the Indian Ocean will, according to the projections, be wholly submerged, and disappear from the face of the Earth. Understandably enough, an Alliance of Small Island States has constituted itself, militantly opposed to further increases in greenhouse gases. Devastating impacts are also predicted for Venice, Bangkok, Alexandria, New Orleans, Miami, New York City, and more generally for the highly populated areas of the Mississippi, Yangtze, Yellow, Rhine, Rhône, Po, Nile, Indus, Ganges, Niger, and Mekong rivers. Rising sea level will displace tens of millions of people in Bangladesh alone. There will be a vast new problem of environmental refugees—as populations grow, environments deteriorate, and social systems become increasingly incompetent to deal with rapid change. Where are they supposed to go? Similar problems can be anticipated for China. If we keep on with business as usual, the Earth will be warmed more every year; drought and floods both will be endemic; many more cities, provinces, and whole nations will be submerged beneath the waves—unless heroic worldwide engineering countermeasures are taken. In the longer run, still more dire consequences may follow, including the collapse of the West Antarctic ice sheet, its surge into the sea, a major global rise in sea level, and the inundation of almost all coastal cities on the planet.