Obviously, the most straightforward way to stop the frighteningly rapid rate of climate change is to reduce humans’ output of carbon dioxide by 60 to 80 percent. But that would require imposition of large-scale, politically unpopular conservation measures in the U.S., a nation addicted to gasoline-thirsty SUVs and plentiful electricity from coal-burning power plants. And good luck with convincing China and India to do anything that might possibly cool their rapidly growing economies. Daunted by the difficulty of changing human behavior quickly enough to avert environmental catastrophe, some scientists are proposing a range of massive geoengineering projects and other extreme measures.

Simulating Volcanic Eruptions

The 1991 eruption of Mount Pinatubo in the Philippines sent an estimated 20 million tons of sulfur dioxide high into the stratosphere. Winds proceeded to spread it all over the planet, forming a high-level haze that reflected back light from the sun and reduced global temperature by 0.5 degrees Celsius. Nobel prize-winning atmospheric chemist Paul Crutzen has proposed simulating the Pinatubo effect by using artillery guns or balloons to inject sulfur into the atmosphere. (Rockets filled with sulfur could also do the trick). Crutzen calculates that the cooling effect would begin within six months and last for up to two years. Artificially duplicating Mount Pinatubo’s effects each year might cost $250 billion, though Crutzen says a relatively affordable $25-$50 billion worth would be enough to make a difference. A major downside is the possibility of creating acid rain or wreaking havoc with global weather patterns, as the eruption of the Indonesian volcanic island of Krakatoa did in the 1880s.

Lenses in Space

University of Arizona astronomer Roger Angel has suggested using non-polluting, magnetically-powered vehicles—a concept that NASA is already exploring—to transport trillions of lenses made of silicon nitride film into space and deposit them near inner Lagrange point 1, an area where the combined effect of gravity of the Earth and the Sun would keep them in the same place relative to Earth’s rotation. The lenses would be about three feet across but incredibly thin, weighing about a gram. Rather than blocking sunlight, they would bend some of it slightly away from Earth, reducing the amount of energy transmitted by about 2 percent. Manufacturing the immense quantity of lenses and putting them into space—some 20 million launches would be required—make Angel’s idea a lengthy and pricey one, but he has estimated that the cost would average out to $100 billion annually over the lenses’ 50 year lifetime. The lenses would also be difficult to turn “off” if necessary, and could lead to uneven cooling effects.

Replanting Forests

Trees and plants are a major bulwark against climate change as they consume carbon dioxide during photosynthesis. The United Nation’s Food and Agriculture Organization estimates that forests have the potential to absorb into their biomass up to 15 percent of global carbon emissions in the first half of the 21st Century—assuming we still have forests by then. About half of the world’s forests already have been cut or burned down to harvest timber or clear land for building or farming, and by 2030, only 20 percent might remain. The destruction of forests, in fact, pumps 1.6 billion tons of carbon into the atmosphere, accounting for 25 to 30 percent of the planet’s greenhouse gas emissions. Reforestation projects could undo some of this damage and help reduce the rate of climate change. Carbon offset trading firms already are planting trees on a modest scale, and governments in developing countries have launched larger efforts. Ethiopia, for example, planted 700 million trees in 2007, and Indonesia planted 79 million trees in a single day last November as part of a global campaign to plant one billion trees. But making a major dent in global warming would require an even bigger multinational push.

Seeding the Oceans With Iron

In the 1980s, oceanographer John Martin analyzed nutrient levels in seemingly desolate stretches of the oceans, and concluded that a scarcity of iron was limiting the growth of the microscopic plant life known as phytoplankton. Since phytoplankton, like other plants, consumes carbon dioxide, Martin was struck with an idea that promised not only to revive aquatic ecosystems but curb global warming in the process. He wanted to seed the oceans with large quantities of iron, artificially stimulating phytoplankton blooms that would sequester carbon and, as the tiny plants died, drag it down to the ocean bottom. “Give me a half a tanker of iron, and I will give you another ice age,” he once argued. Since Martin’s death in 1993, others have become enamored of the so-called “Geritol Solution” for global warming. Proponents argue that 15 tankers steaming across the polar oceans all year with a projected cost of about $10 billion, would be enough to absorb most of the 3.5 gigatons a year increase in carbon dioxide emissions expected between now and 2020. Critics argue that artificially inducing large phytoplankton blooms could have disastrous ecological consequences, such as the creation of toxic tides that would endanger fish, marine mammals, and birds.

Turning Pollution Into Baking Soda

Burning coal to generate electricity is one of the planet’s major sources of carbon emissions. To cope with their seemingly insatiable demand for electric power, the U.S., China, and India plan to build 850 new coal-fired plants by 2012, which will spew five times as much carbon dioxide into the atmosphere as the Kyoto Protocol nations aim to eliminate. Many believe that carbon sequestration, in which carbon dioxide emissions from smokestacks are trapped and stored, is the best answer. But most ideas for what to do with the carbon dioxide—such as pumping it into manmade caverns—would be costly, and there’s always the risk that the gases will escape. That’s where a Texas-based startup company, Skyonic, and its innovative new carbon sequestration technology, gets involved. Plastic mesh sheets capture 90 percent of the carbon dioxide emitted by a power plant, which is then mixed with sodium hydroxide to produce harmless baking soda. Solids are easier to store, and since the baking soda produced is high-grade, it can be recycled for industrial applications or even used for baking. Texas utility Luminant installed a pilot version of the technology at its Brown Steam Electric Station in 2006, and Skyonics is now designing a system that it hopes to install on a large 500-megawatt power plant in 2009.

Creating Artificial Weather

Based upon an idea conceived in 1990 by atmospheric physicist John Latham of the U.S. National Center for Atmospheric Research in Colorado, University of Edinburgh engineer Stephen Salter has proposed the most massive weather modification project ever. He would build and dispatch a $950 million fleet of 500 unmanned robotic wind-powered ships off the west coast of Africa and in the Pacific, west of Peru, places where low-lying stratocumulus clouds are abundant. The forward movement of the ships would turn underwater turbines attached to their hulls, generating enough electricity to create an electrostatic field, which would cause sea water sucked into the rotors to be sprayed in a fine mist that would carry tiny particles of salt into the clouds, increasing their density and whiteness and making them more reflective. By artificially increasing the estimated 40,000 tons of sea spray already whipped up into the atmosphere each second by a mere half ton, Salter says the sky would reflect 4 percent more solar energy back into space, offsetting global greenhouse gas emissions. An additional 500 ships would have to be deployed each year to keep pace with the rising amount of carbon that civilization is pumping into the atmosphere. One concern about this proposed idea is its potential to change weather patterns on land.

Turning Deserts and Islands Into Mirrors

The surface of the Earth/atmosphere’s albedo—that is, the amount of sunlight that it reflects back into space—averages about 30 percent, but in areas covered by white ice and snow, it can reach 90 percent. That’s why the melting of the polar ice caps threatens to accelerate the global warming process even more. Conversely, however, if we could somehow make more of the Earth’s surface as reflective as the ice caps, climate change might be slowed. To that end, Internet amateur eco-futurists have advocated laying immense sheets of Mylar or some other reflective material across deserts, which have a relatively low natural albedo of 40 percent, to reflect more of the sun's energy back into space (Another similar idea is to float immense artificial islands of white plastic in the oceans). One online advocate determines that to gradually cool the planet by one degree, the scale of such a project would have to be immense, such as covering 37% of the Sahara Desert, or about 1.2 million square miles. This would cost an estimated $24 billion over ten years. One flaw in the plan is that it would require polyester film to be manufactured in unprecedented quantities, which in itself would add to the planet’s carbon emissions. In addition, skeptics envision the devastating effect that such a scheme might have on fragile desert ecosystems, and point to the inherent difficulty of protecting the thin, lightweight sheets from harsh desert conditions.

Source: National Geographic