Environment

Fighting climate change with science

Some scientists believe geo-engineering could be the answer to climate change. Here are six ideas.
  • Dec 31, 2012
  • 631 words
  • 3 minutes
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When the Haida Salmon Restoration Corp. dumped 100 tonnes of iron-rich dust into the Pacific Ocean 370 kilometres west of Haida Gwaii, B.C., last summer, creating a 10,000-square-kilometre plankton bloom meant to attract fish and absorb carbon dioxide from the atmosphere, it fanned the flames of controversy surrounding ocean fertilization. But this isn’t the only geo-engineering idea that’s being tossed around as a solution to the planet’s climate woes. Here are a few of the more interesting ones.

Stratospheric aerosols Using atmospheric research models, scientists at the University of California, Los Angeles, found that spraying sunreflecting chemical particles into the atmosphere would mimic the effects of a volcanic eruption and block enough sunlight to cool the Earth, offsetting the temperature increase caused by carbon dioxide. Yet the models can’t predict how these “artificial volcanoes” would affect the ozone layer, rainfall and food supplies, and the lack of sunlight would reduce solar-power capabilities.
Deflecting sunlight in space Of all the geo-engineering ideas out there, this one is literally out there. Lowell Wood, an astrophysicist at the Lawrence Livermore National Laboratory in California, has proposed positioning a giant mirror made of a fine mesh of aluminum threads between the Earth and the sun. The mirror could deflect one to two percent of solar radiation, helping cool the planet. The downside? Uneven cooling could make the poles warm and the tropics cool, and the mirror would have to span 1.5 million square kilometres.
Cloud brightening Cloud physicist John Latham of the U.S. National Center for Atmospheric Research believes that specially designed ships could be used to spray seawater into the sky, where particles of sea salt would act as the nuclei around which extra cloud droplets would form. The more droplets there are, the larger and more reflective the cloud becomes, keeping more solar energy away. But clouds don’t last forever, which means the seawater would need to be sprayed into the atmosphere indefinitely.
Biochar What do you get when you heat crop waste and other types of biomass in a low- or zero-oxygen environment? If you guessed biochar, a carbon-rich charcoal product that is more resistant to decomposition and therefore locks in carbon for a longer time than, say, decaying plant matter, you’d be right. Biochar’s carbon can be safely stored in soil for years, while helping improve agricultural productivity, but it’s debatable whether the idea, which was used as early as 8,000 years ago in the Amazon rainforest, could work on a large enough scale to be worthwhile.
Ambient air capture Carbon Engineering, a Calgary-based company, uses industrial-sized fans to mimic the work of the Earth’s trees and plants, trapping and removing carbon dioxide from the atmosphere. Although the process can pull in up to 500,000 tonnes of emissions per square kilometre per year, the carbon dioxide isn’t completely removed from the carbon cycle; instead, it’s reused to run the air-capture facilities or is sold to make products such as jet fuel.
Enhanced weathering Leave it to a geo-engineer to find a way to speed up the Earth’s natural processes to fight climate change. Enhanced weathering involves purposefully exposing large quantities of crushed minerals that will react with atmospheric carbon dioxide, such as magnesium silicate, and storing what’s produced in the soil or the ocean. Unfortunately, the energy and cost required to mine and crush the minerals are far greater than the amount of carbon dioxide that could be removed from the atmosphere.
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