Guest post by Owen Paepke.

The globe is warming because incoming solar energy exceeds the heat lost through an atmosphere laden with GHGs. This kind of systemic energy imbalance is a common engineering problem, and any first year thermodynamics student knows to attack it on both ends—increase outflow and decrease inflow. But our policy makers and opinion shapers apparently flunked thermo. All of the effort is being focused on the first approach, which is likely the expensive and long lead side of this equation.

Increased particulates in the atmosphere reduce the amount of sunlight absorbed by the planet. The best known natural experiments verifying that result were called Krakatau, Pinatubo, and Tambora. A more sustained example was global “dimming:” beginning in the 1940s, the planet began to cool. By the 1970s, predictions of a new ice age abounded in popular media. Scientists soon identified the culprit: air pollution was blocking sunlight. In 1970, however, the U.S. enacted the Clean Air Act. European countries soon followed. These initiatives had nothing to do with global dimming; the same pollutants at ground level were affecting peoples’ health. The Clean Air Act sharply reduced these pollutants, the skies cleared, and solar heating returned to natural levels. Because carbon dioxide has never been considered a pollutant, however, those emissions went unregulated and continued to rise. The greenhouse effect arrived with a vengeance. It is ironic that a great environmental success story is partly responsible for Global Warming.

It seems likely that the sunlight-blocking effect of particulates could be engineered and controlled. The most effective reflectors from volcanic eruptions are aerosols of minute particles that spread through the stratosphere. UC Irvine Physics Prof Gregory Benford therefore recommends trying stratospheric introduction of tiny particles of diatomaceous earth, a cheap mineral that is essentially inert. Such particles would be stable in the upper atmosphere and completely harmless when they fell to earth, mixing imperceptibly with the dirt. If the “particle shield” proved effective, it could be maintained for around $1 billion per year, a paltry sum when compared to even the lowest cost estimates for effective reductions in carbon emissions.

Another approach would be the “Cloud Shield” proposed by atmospheric physicist John Latham. Latham hypothesizes a fleet of around 1,000 robotic “cloud boats” scattered around the vast emptiness of the low latitude oceans, each spraying one micron droplets of sea water into the air. These aerosols would both enlarge the naturally occurring stratocumulus clouds and increase their reflectivity. Latham calculates that such a fleet might reduce the planet’s total solar energy absorption by as much as three percent, enough to counterbalance the effects of GHG emissions.

The cost estimates are again quite low. Even if each of the 1,000 boats cost $1 million per year to maintain, the annual tab would be $1 billion. The approach is environmentally benign—ocean water would rain on the ocean. If any problems emerged, the system could be shut off and its effects stopped either regionally or globally within a few days, as natural processes restored the clouds to their normal sizes and densities.

These two approaches could complement each other. A stratospheric particulate layer might bring the global heat equation closer to balance, with the number and activity of the cloud boats being adjusted according to measurements of solar energy intensity and climatic indicators. The almost instantaneous responsiveness of the cloud boats would lend itself to this kind of fine tuning. Even if each approach cost $1 billion per year, the total would still be only a tiny fraction of the cost of stringent carbon emission reductions.

Environmentalists cry that we should eliminate the problem rather than treating the symptoms, but this quickly devolves into a semantic argument. Is the ultimate problem excessive GHG emission, or is it Global Warming? In any event, there is nothing wrong with curing an existing problem while learning how best to address its root cause. After Pasteur discovered microbes, should all efforts have been directed toward antiseptics, or were antibiotics a good idea too? Should we have let all the AIDS victims die while we searched for a vaccine? In the environmental arena, treatment of drinking water long pre-dated the Clean Water Act, saving countless lives. The goal should be to address Global Warming in the quickest and most efficient manner, whether by prevention or cure, and most likely using both.

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