September 1, 2007
Stephen Schwartz knows as much about the effects of aerosols on climate change as anyone in the world, and he’s worried. He believes climate change is so massive an economic issue that we face costs “in the trillions if not quadrillions of dollars.” He thinks a Herculean effort and great sacrifice is required to get the world down to zero net increase in carbon dioxide concentrations, an effort he compares to that which the Allies undertook in their all-out war against Nazi Germany and Japan.
“Recall World War II, where everyone was making a sacrifice: gas rationing, tire rationing, no new car production, food rationing,” he explains. “I don’t think the people of the world are ready or prepared to make such a level of personal sacrifice. Perhaps when the consequences of climate change become more apparent that will change. But by that time, there will be irreversible changes in climate.”
Few scientists speak with more conviction, or lay out the potential consequences of inaction more starkly. Yet Stephen Schwartz, senior scientist at Brookhaven National Laboratory, chief scientist of the Atmospheric Science Program of the United States Department of Energy, and author of the study some credit with spurring acid rain legislation in the 1990s, is also Al Gore’s worst nightmare. He knows the science on global warming is not settled, as Gore claims. He knows society has antidotes to carbon dioxide − aerosols − that could postpone the day of reckoning far into the future. And although he dreads a reliance on the aerosols, he knows respected scientists are pursuing aerosol-abatement strategies, and that they could be cost effective and environmentally benign.
Aerosols are liquid or solid substances suspended in air. Many aerosols, such as those associated with cloud formation or those that stem from volcanic emissions, occur naturally. Others, such as emissions from automobiles, smokestacks and coal plants, come of industrial activity.
We know a lot about the carbon dioxide that comes of fossil fuel burning. But we know relatively little about the aerosols that industrial activity produces simultaneously. What we do know will surprise many people: The aerosols act as cooling agents, counteracting the warming effect of the carbon dioxide. Every lump of coal, in effect, contains a store of substances, some of which warm, some of which cool, the atmosphere.
Dr. Schwartz thinks he has a good handle on the degree of warming that comes of carbon dioxide. Here the science is fairly straightforward, he says, because we know how much carbon dioxide enters the atmosphere, we know how long it stays there − 100 years − and we know its distribution is fairly uniform globally.
But he doesn’t know how much cooling aerosols provide − the uncertainty surrounding aerosols’ cooling properties has long been a dominant mystery in the climate change field. He can say the amount of cooling is very substantial, likely offsetting most of the carbon dioxide the planet produces, and possibly much, much more − the uncertainty is that great. Conceivably, aerosols are so effective at cooling that humans could double the amount of coal, oil and natural gas we burn and find that aerosols entirely negate the warming for centuries to come.
Getting a handle on how much cooling comes of aerosols is daunting in the extreme. The aerosols come from literally billions of sources producing aerosol precursors that are oxidized in the atmosphere at varying rates, depending on their photochemical surroundings, which are themselves highly variable in space and time. Not only do the myriad aerosols vary in size and composition, they act differently depending on their sources, they interact unpredictably, and they are replaced every week with new generations of aerosols.
With enough time and money − at least a decade if this area of research becomes fully funded − research by Dr. Schwartz and others might make demonstrable headway in reducing the uncertainty surrounding aerosols’ cooling properties. More likely several decades will be needed, because those who hold the purse strings have refused to see the paramountcy of this area of research. Although the work that needs to be funded on aerosols was spelled out in a 1996 National Academy of Sciences report, Dr. Schwartz laments, “the funding agencies have essentially ignored the urgent needs that the report spelled out.”
As a result, the science in this potentially decisive area of climate change remains undone, and the state of the knowledge has made precious little advance. Without knowing the extent of cooling from aerosols, we can’t know the extent of warming that threatens the Earth.
But no amount of funding for research can solve another mystery concerning aerosols, a mystery that is entirely unknowable, and one that may make the uncertainty over aerosols’ cooling properties dwarf in importance. Knowing the future of aerosols requires having a crystal ball that can tell us what the global economy − and its production of aerosols − will look like decades or centuries hence.
The ability of aerosols to counteract the warming from man-made carbon dioxide will continue as long as aerosols increase their presence in the atmosphere at an exponential rate, Dr. Schwartz explains. This exponential rate has existed to date, as the historic record demonstrates. But eventually, Dr. Schwartz believes, for some reason or another aerosols will stop growing at an exponential rate, and when this occurs, the global warming threat could hit us with full force.
Or, with aerosols as an artificial remedy, it could not.
Aerosols do not need to be produced as a byproduct of industrial activity. They could be manufactured specifically to counteract greenhouse gases, for example via aerosol-producing wind-driven generators that would artificially brighten marine stratus clouds, an option that Dr. Schwartz thinks is likely to be environmentally benign.
These aerosol generators − human-controlled global thermostats − might give society the ability to offset the negative effects from carbon dioxide production. The issue would then not be environmental so much as economic, the choice being to abate carbon dioxide via a Kyoto-type treaty in order to bring down carbon dioxide levels, or to abate carbon dioxide’s warming effects via environmentally benign aerosols. Faced with this choice, society may well be better off burning fossil fuels so as to maximize economic growth, and then using part of the increased wealth for future aerosol production, should it prove necessary.
“I think a strong argument can be made along those lines,” Dr. Schwartz acknowledges, although he thinks the more prudent course lies in cutting carbon dioxide emissions today, rather than postponing the inevitable. That argument − whether the pain of going onto a war footing today is worth the future gain − ultimately belongs in a non-scientific forum, not with him. “My job as a scientist is to do the research upon which sound policies can be based. Once we have the research, society can make an informed decision.”
Lawrence Solomon is managing director of Energy Probe Research Foundation and executive director of its Urban Renaissance Institute.
CV OF A DENIER
Stephen Schwartz, an award-winning scientist at Brookhaven National Laboratories, is author or co-author of some 340 journal articles, proceedings, reports and reviews. He received his PhD from the University of California, Berkeley. Dr. Schwartz is a Fellow of the American Geophysical Union and of the American Association for the Advancement of Science.