Over the past year, if you looked west a few minutes after sunset on a clear night, you could see a spectacular brightness in the sky. You might have noticed how the pale violet overhead melted closer to the horizon into an orange of astonishing intensity, and that the light show lasted for much longer than usual. That’s because after the sun slips beyond Earth’s horizon, its light continues to shine 10 miles up for 15 minutes, and lately there’s been more dust in the atmosphere to scatter the light back to our eyes.
Such sunsets as we’ve been having remind me of the metaphor that likens the life-supporting veil of air around the Earth to the pigmented outer skin of an orange. Our planet is 8,000 miles in diameter, but our atmosphere contains most of its mass in just the first five miles of air. In other words, the layer of air enfolding Earth is not very thick at all. When dust or gases are sent into the atmosphere, there’s only a limited amount of space in which their molecules can circulate; thus a relative few can have a huge effect.
In fact, the flamboyant sunsets we’ve been seeing are the result of a single volcano, Mount Pinatubo, which erupted in the Philippines in June 1991, sending 20 megatons of sulfuric acid (the stuff in L.A. smog) into the air. This is not the first time Earth has seen its like. The brilliant flaring skies on the canvases of English artist J.M.W. Turner were painted shortly after Mount Tambora erupted in Indonesia in 1815. That blast put up to 200 megatons of sulfuric acid some 10 to 15 miles up in the stratosphere, where the veil of dust and gas lasted for several years.
But if we on Earth can see the dust, then obviously the sun can see it, too. And the sun is the prime mover of our climate. That solar thermonuclear reactor provides us with about 290 watts of radiant heat over each square yard of Earth. That’s roughly equivalent to a hair dryer on low heat, which may not sound like much. But when you consider that there are some 585 trillion square yards on Earth, that amounts to some 17 million billion watts.
Of course, the veil of dust from Mount Pinatubo’s blast doesn’t float overhead only at twilight. It’s there all day, deflecting sunlight from its normal path to Earth. Even 1 percent less solar heating is equivalent to a loss of about three watts of radiant heat per square yard, or some 1,700 trillion watts for the planet as a whole. Tambora’s eruption in 1815 was followed by the legendary 1816 summer that never came in New England and Europe. Until Pinatubo blew its stack last year, no volcano had remotely challenged Tambora for its climatically significant sulfur injection. But Pinatubo was enough to push 1991, which started out as the warmest year on record, into second place behind 1990. Many estimates went on to predict that because of Pinatubo’s pall 1992 would be up to one degree cooler than the global average of the past decade. And that prediction seems to be holding up.
These events show that if something interferes with the sunshine reaching Earth, then climate is likely to be affected. But our planet also radiates heat back to space to maintain its thermal balance--what if something interferes with that? Over the past century the planet as a whole has warmed up in fits and starts by about a degree. Overall, the 1980s were the warmest decade ever recorded since global thermometer records were first assembled 150 years ago. This warming trend has spawned a major scientific and political debate. Is it natural? Or have humans enhanced it? Is it a threat we should do something about?
The culprits most often blamed for global warming are our fossil- fuel-based technology and the rapid clearing and torching of forests by the world’s ever-growing population. Since burning fossil fuels and trees produces carbon dioxide, and since human activities have augmented the carbon dioxide in nature by some 25 percent since the industrial revolution began, environmentalists have increasingly argued for stabilizing, then lowering emissions of this greenhouse gas. This is the position Japan and most European nations took at the Earth Summit in Rio de Janeiro in June. The key question was, What position would our environmental president take, since the United States is the world’s most prolific polluter, and since this country’s cooperation (not to mention financial assistance) will be essential to slow down global CO2 emissions?
The White House, some business groups, and a few contrary-minded scientists had always argued that the possibility of a nasty greenhouse effect was too uncertain to justify spending billions of dollars to fix it. They (as the tobacco industry has done for decades with smoking) called instead for further studies. Yet the greenhouse effect itself is neither new nor controversial. It has been known for almost 150 years that atmospheric gases such as water vapor, carbon dioxide, methane, and nitrous oxide have the capacity to trap most of Earth’s radiative heat near its surface--an effect that accounts for about 60 degrees of perfectly natural greenhouse warming. Indeed, there was speculation a century ago that the burning of fossil fuels would increase the greenhouse effect by adding carbon dioxide to the atmosphere. Human industry has caused not only a 25 percent increase in carbon dioxide but also a 100 percent rise in methane and has introduced such unnatural chemicals as chlorofluorocarbons (CFCs), implicated both in global warming and in creating the ozone hole.
It is also not controversial that these greenhouse gases have helped trap about two to three watts per square yard of extra radiative energy near Earth’s surface since the industrial revolution. (That’s equivalent to the power of one small Christmas tree bulb over each square yard of Earth’s surface.) In other words, people have already shown, albeit inadvertently, that they can compete with nature as the power behind the weather.
What is controversial is how to translate those extra watts of human-induced heating into X degrees of temperature rise. Most assessments, however, have concluded that temperatures could rise as much as 9 degrees by the year 2100.
Not since the end of the last ice age--a period that totally revamped the ecological face of the Earth--has the global temperature gone up by 9 degrees. (Humans have subsequently never had to contend with a planet that is much more than 3 degrees warmer than at present.) Such a sudden upturn of the thermostat could cause considerable disruption to ecological systems, agriculture, water supplies, and human and animal health. Sea levels might rise as waters expand and ice caps melt, and hurricanes, which form over warm seas, might intensify, threatening the very existence of island nations. My own view is that there’s at least a 50 percent chance of unprecedented warming--that is, of a rise of more than 3 degrees. The chance of a catastrophic rise--9 or more degrees--is, I’d guess, only 10 percent, though it can’t be ruled out.
What, then, should the world’s response be? Should we act now, as a hedge against plausible if uncertain outcomes, or should we wait ten years for more certain data? Environmentalists like Michael Oppenheimer of the Environmental Defense Fund contend that Earth will warm by at least 3 degrees irrespective of what ameliorative steps are taken now. So the only hope of stabilizing climate at a level slightly warmer than it has been is to cut emissions of carbon dioxide and other greenhouse gases by 50 percent or more over the next 50 years. To achieve that, developed countries might have to make dramatic cuts in fossil-fuel consumption. Developing countries might even have to forsake fossil fuels as a basis for development and stop clearing forests to make room for their expanding populations. But critics maintain these measures threaten economic development and discourage competitiveness. Are there alternatives?
One controversial way is to counteract the impact of human activities with large-scale engineering schemes. These Jules Verne-like ideas range from putting iron in the oceans to fertilize more CO2-absorbing plankton to putting huge parasols in space to block 1 percent of the sun’s incoming light. Another suggestion is to inject dust into the stratosphere, using jets or giant rifles, to create a human Pinatubo.
Calculations by the physicist Robert Frosch illustrate the idea: Assume dust lasts one to three years in the stratosphere. Based on computer calculations, we need spread only a seemingly tiny amount of dust (.00059 ounce per yard) in the stratosphere to cause a cooling of two watts per square yard of Earth’s surface--enough to counteract the warming due to greenhouse gases over the past few decades. A 16-inch naval rifle fired vertically could hurl a one-ton shell 12 miles into the stratosphere. The cost of using such a rifle system, Frosch estimates, might be up to $30,000 per ton of dust lifted. As little as 1 million tons a year might do the trick, at a cost of $30 billion. That represents .1 percent of the combined gross national products of the world--a small enough sum to catch people’s attention.
But will it work, could there be side effects, and is it ethical to counteract our assaults on nature with calculated countermeasures? No doubt a number of geoengineering schemes could make an impact on global climate. But will their impact be significant enough, or too significant? Recall, the global forecast is for a temperature rise of anything from 3 to 9 degrees. That’s a factor-of- three uncertainty about how much global warming we’re inadvertently causing. By symmetry, then, there’s a factor- of-three uncertainty as to how much cooling we might achieve through deliberate attempts to modify Earth’s heat balance. Given all that uncertainty, we could simultaneously overestimate global warming and underestimate the impact of our geoengineering attempts to save ourselves, creating a cure worse than the disease. Besides, there are other ways to repair the air, so why take a chance on trying to cure our addiction to polluting the atmosphere with the counterdrug of geoengineering?
Yet I do reluctantly support research on such schemes. Why? First, I want to know what’s possible--I simply couldn’t vote on ideological grounds not to learn. But the real reason is more serious: present projections are as likely to be underestimates as overestimates. What if we are very unlucky and global warming triggers serious climate instability, threatening coastlines, crops, water supplies, who knows what? Apparently we can’t get unhooked from our addiction to fossil fuels, deforestation, and reproduction overnight. But if we don’t start slowing down our assaults on the air soon, we may need risky geoengineering schemes to muddle through while we figure out a better solution. We must know what antidotes are possible, since humanity may well continue to value short- term economic and national profit over long-term global gains.
This summer’s events in Rio amply demonstrated the conflict. Specific provisions for an international treaty on emissions were supposed to be the big-ticket item at the Earth Summit. Yet international negotiations aimed at limiting emissions proved very difficult because of competing interests between developed and developing countries and widely different ideologies and life-styles among the participants. The United States, for example, typically consumes up to 20 times the amount of energy and materials per head that, say, the Maldives does. While Japan and many European countries wanted a treaty with specific targets--cutting emissions to 1990 levels by the year 2000--President Bush balked on the grounds that such restrictions were economically harmful, and he insisted on a nebulous statement of principle instead. China and India--which are counting on cheap fossil fuels as a means of powering industrialization--also initially resisted a treaty with teeth, but some developing countries, including Brazil, Bangladesh, and many island nations, were all for it.
Yet I’m convinced that some solutions could be acceptable to most nations, at least for a decade or so, until we’ve developed better alternatives, like affordable solar energy. Cutting emissions can be compatible with positive economic development, particularly if you achieve it through energy efficiency. In this country, analyses by the Office of Technology Assessment and the National Academy of Sciences have both concluded that current practices in energy production, housing, transportation, agriculture, and industry fell well short--from 10 to 40 percent short--of what can be achieved by state-of-the-art technology. Initial capital outlay for technologies that consume less fuel, moreover, could be made up in 5 to 30 years. True, developing countries that have neither the capital nor the technical expertise to invest in cleaner energy would need assistance from the world’s richer nations. But the concerted investment would pay off in more ways than one--not just by lowering greenhouse gas emissions but also by reducing acid rain, unhealthy air pollutants, and dependence on imported oil.
In fact, many approaches to curbing emissions offer attractive collateral benefits. By reducing deforestation, many developing countries could cut carbon dioxide emissions from fires while at the same time sustaining the absorption of greenhouse gases by vegetation and helping preserve wild species. By limiting population growth they could ease the pressure to clear land to house and grow food for their people and reduce competition for scarce resources--with the collateral benefit of raising per capita living standards. The tough question is not whether to carry out such policies but how far to push them and who should pay. So far, aid commitments made by the United States look pathetic compared with those made by Japan and the 12 European Economic Community countries.
Indeed, to sustain development and preserve our environment will probably require investment on the order of tens to hundreds of billions of dollars annually for decades. Bear in mind, though, that the world’s nations have been spending some trillion dollars annually on defense. The investment needed to provide environmentally sustainable development, as it’s called, is small potatoes by comparison. If the world community cut back its investment in defense and put the savings toward this larger cause, it could declare war on underdevelopment, overpopulation, waste, environmental damage, and pollution of the atmosphere.
So the next time you admire the spectacular sunsets created by nature’s own volcanic smog, don’t forget that this is her fiery reminder that we live and breathe in a thin veil of safety. Its ethereal future is now increasingly in our hands.