Some of the most dramatic measures to suck global warming pollution out of the atmosphere are probably too risky to be worth trying, an academic at a climate research institution concluded.
Phil Williamson, a scientist at the University of East Anglia in the U.K., examined the ecological effect of a number of proposed methods known as “geoengineering” and concluded none would work at a large scale without huge risks for the planet.
“We have to concentrate on reducing emissions,” Williamson said in a phone interview. “We could cool the world in all sorts of weird and wacky ways that seem like they could be technically possible, but whether they will actually work on a large scale is a big question and what kind of disruptions they would cause is another.”
Geoengineering long has captured the attention of researchers looking for an easy way to suck up the fossil-fuel emissions blamed for global warming. Models for predicting the long-term effect of humans on the planet often contain the assumption that it will be possible to eliminate large amounts of carbon dioxide from the atmosphere.
The ideas have gone nowhere partly because policymakers would face a moral dilemma in conducting what’s essentially a science experiment on the entire planet. Still, the dream persists. Billionaire Richard Branson, chairman of Virgin Group Ltd., said in 2007 he would award $25 million to a company that develops a technology that can remove greenhouse gases at a rate of 1 billion tons per year. He has yet to pay out the prize money.
Williamson’s work builds on previous research from the University of East Anglia, one of the key institutions supplying global temperature data interpreted by the United Nations Intergovernmental Panel on Climate Change. In 2014, Nem Vaughan from the school’s environmental science program concluded that geoengineering shouldn’t be considered a “quick-fix” solution to climate change.
There have been dozens of suggestions, but none to date should be considered a real solution, according to Williamson. These are some of them:
- Pouring nutrients such as iron into the ocean. What is it? Boosting algae and seaweed growth with added nutrients because they absorb carbon dioxide just like other plants.
Why it may not work: The carbon dioxide in the algae and seaweed will be released when they eventually die and decompose. Also an increase in these populations may disrupt underwater ecosystems and displace fish and other marine life.
- Greenhouse gas-absorbing rocks. What is it? Scattering certain types of stones known as silicates because they soak up carbon dioxide as they weather.
Why it may not work: To reduce carbon dioxide by 12 percent from current levels, up to 5 kilos (11 pounds) of silicate rock would have to be in every square meter of nearly half of the planet’s surface, according to Williamson. The volume of rock mined would need to exceed the global coal industry with costs estimated to be up to $600 trillion.
- Biochar. What is it? Storing carbon in soil by plowing fields with charcoal.
Why it may not work: It could raise competition for land use. Darkening millions of hectares of soil may also increase the Earth’s heat absorption, like how wearing a black T-shirt on a hot day is a bad idea. The long-term effects on soil are also unknown.
- Afforestation. What is it? Planting trees in an area that wasn’t a forest previously because they store carbon dioxide as they grow.
Why it may not work: Planting forests could result in the loss of natural ecosystems and cause changes to the soil-water balance and cloud cover. This could actually have a net warming effect, according to the paper.
- Bioenergy with carbon capture and storage. What is it? Growing crops to burn in power plants and capturing the carbon dioxide this emits with technology.
Why it may not work: In order to have a significant impact, bioenergy crops would need to be planted on an area about half the size of the U.S., according to Williamson. It would compete with food for land use and the use of fertilizers could actually increase greenhouse gas emissions. Carbon capture and storage is costly and not in advanced stages.
- Carbon dioxide-sucking machines. What is it? A contraption that removes carbon dioxide from the air with a filtration system and chemicals.
Why it may not work: Implementing it on a large scale would be extremely expensive with costs estimated to be around the same as the carbon- absorbing rocks.
For a method to have a real impact, it has to be feasible, cost-effective and socially acceptable, the paper said. Some methods tick two of these boxes, but none have all three.
“We could probably remove carbon dioxide from the atmosphere in modest amounts with the chemical method with machines if we are prepared to pay for it,” he said. “It can be done but on a small scale and it would be very expensive.”