A wild idea to combat global warming suggests creating an artificial ring of small particles or spacecrafts around Earth to shade the tropics and moderate climate extremes.

There would be side effects, proponents admit. An effective sunlight-scattering particle ring would illuminate our night sky as much as the full Moon, for example.

And the price tag would knock the socks off even a big-budget agency like NASA: $6 trillion to $200 trillion for the particle approach. Deploying tiny spacecraft would come at a relative bargain: a mere $500 billion tops.

But the idea, detailed today in the online version of the journal Acta Astronautica, illustrates that climate change can be battled with new technologies, according to one scientist not involved in the new work.

Mimic a volcano

All scientists agree that Earth gets warmer and colder across the eons. A delicate and ever-changing balance between solar radiation, cloud cover, and heat-trapping greenhouse gases controls long-term swings from ice ages to warmer conditions like today.

Those who are often called experts admit to glaring gaps in their knowledge of how all this works. A study last month revealed that scientists can't pin down one of the most critical keys: how much sunlight our planet absorbs versus how much is reflected back into space.

Nonetheless, most scientists think our climate has warmed significantly over the past century and will grow warmer over the next hundred years. Various studies claim the planet is destined to warm by anywhere from 1 to 20 degrees Fahrenheit over the next few centuries. Seas will rise dramatically, the scenario goes, inundating coastal cities. But another group of scientists argue that the temperature data supporting a warming planet is not firm and that projections, based on computer modeling, might be wildly off the mark.

Either way, perhaps our fate is more in our hands than we might have imagined.

"Reducing solar insolation by 1.6 percent should overcome a 1.75 K [3 degrees Fahrenheit] temperature rise," contends a group led by Jerome Pearson, president of Star Technology and Research, Inc. "This might be accomplished by a variety of terrestrial or space systems."

The power of scattering sunlight has been illustrated naturally, the scientists note. Volcanic eruptions, such as that of Mt. Pinatubo in 1991, pumped aerosols into the atmosphere and cooled the global climate by about a degree. Other researchers have suggested such schemes as adding metallic dust to smoke stacks, to flood the atmosphere and reflect more sunlight back into space.

In the newly outlined approach, reflective particles might come from the mining of Earth, the Moon or asteroids. They'd be put into orbit around the equator. Alternately, tiny micro-spacecraft could be deployed with reflective umbrellas.

A ring created by a batch of either "shades the tropics primarily, providing maximum effectiveness in cooling the warmest parts of our planet," the scientists write. An early version of their idea was presented but not widely noticed in 2002.

Eccentric but reassuring

Those researchers who don't buy the argument that global warming is occurring at any significant rate nor that humans are largely to blame may warm up quickly to the new idea.

Benny Peiser, a social anthropologist at Liverpool John Moores University in the UK, tracks climate research and the resulting media coverage. He's among the small but vocal group that goes against mainstream thought on the topic of global warming.

"I don't think that the modest warming trend we are currently experiencing poses any significant or long-term threat," Peiser told LiveScience. "Nevertheless, what the paper does show quite impressively is that our hyper-complex civilization is theoretically and technologically capable of dealing with any significant climate change we may potentially face in the future."

Peiser also notes that the Kyoto Protocol, a global agreement to reduce greenhouse gas emissions, is estimated to cost the world economy some $150 billion a year. He also sees a broader rationale for supporting the seemingly bizarre manner of managing Earth's temperature budget.

"I believe that this mindset, despite its apparent eccentricity, is actually rather reassuring," Peiser said. "It provides concerned people with ample evidence of the extraordinary human ingenuity that, as so often in the past, has helped to overcome many predicaments that were regarded as impenetrable in previous times."

He also sees an ultimate big-picture reasoning to look favorably on the notion of controlling Earth's climate.

"Whatever the cost and regardless of whether there is any major risk due to global warming," Peiser said, "it would appear to me that such a space-based infrastructure will evolve sooner or later, thus forming additional stepping stones of our emerging migration towards outer space."

Earth's Atmosphere

An illustration of the ring of particles or spacecraft casting a shadow on equatorial Earth. To keep the particles in place, gravitationally significant shepherding spacecraft might be employed. They would herd the particle much like small moons keep Saturns rings in place.

Credit: Star Technology and Research, Inc.