How to get the carbon dioxide we shoved into the atmosphere back out again

Environmentalists get nervous when they hear people talking about reducing carbon-induced global warming through “geoengineering”, the use of technology to intervene directly in the Earth’s systems to reduce the impact of climate change.

This nervousness is understandable given we got ourselves into this climate emergency mess through the intensive pursuit of energy-hungry technologies as a way to improve living conditions on the planet. Unfortunately, in the process we also managed to cause serious damage to the environment leaving ourselves open to an uncertain long term future.

There are lots of examples of how we might use technology to get the carbon dioxide we shoved into the atmosphere back out again. Some are very straightforward; for example planting replacement forests for the ones we are busily chopping down on a daily basis today.

The fear is that once a geoengineering response is applied there may be no shutting it down

Trees hold on to vast amounts of carbon and use the gas as a feedstuff to produce sugars through the process of photosynthesis. This looks like a viable solution to our carbon problem until you realise that tree growth is slow and we have to retain a certain level of farmland to feed ourselves.

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It does not represent a quick fix, although there is at least some level of carbon benefit and trees can be planted just about anywhere, so we all can become actively involved in this one.

Another approach – and one that many countries are actively studying – is carbon capture and storage. This involves tapping into a carbon dioxide source; for example from a coal-fired power plant, extracting the gas, and then pumping it into suitable deep rock formations as a way to lock up the carbon for many years to come.

This one costs a lot more than the tree option and we have to take it on faith that the gas won’t manage to seep out decades or a century from now. It is also unclear whether this can be done on a scale large enough to achieve a meaningful reduction in atmospheric carbon dioxide levels.

There are also some particularly mad ideas out there. One proposes spraying the ocean’s surface with foaming agents creating a temporary layer of “microbubbles” that would persist on the ocean’s surface thereby increasing the water’s reflectivity.

Dark surfaces such as open ocean and land absorb more solar energy than they reflect, thereby warming these surfaces. Ice and snow are the reverse, reflecting 70 to 90 per cent of the solar energy back into space.

The term for this reflectivity factor is “albedo” and the higher the albedo the better when it comes to global warming. You can see how the warming Arctic has meant a slowly rising albedo as the sea ice and Arctic snow cover melt away.

Serious drawbacks

The microbubbles would increase the ocean’s albedo but there are serious drawbacks. Substances such as latex or polystyrene would be used to help the bubbles persist on the water’s surface, long lasting pollutants that would persist to unknown effect.

The bubble mats would also inhibit oxygenation of the seawater and reduce the sunlight reaching plankton, the foundation of the marine food web.

Whatever method might emerge it is clear it would have to be pursued on a colossal scale if it was to have any impact on the 2,000 gigatonnes of carbon dioxide we have placed in the atmosphere since the Industrial Revolution.

The fear is that once a geoengineering response is applied there may be no shutting it down. There might be some unforeseen runaway effect that could further damage the atmosphere.

The payback is even better if the price of the carbon saved is taken into account

Researchers from Oxford and from Russia believe the answer to our problems may be as simple as letting the grass grow again over vast areas of Arctic tundra, in the process delivering a massive carbon sink and a process that should increase Arctic albedo.

During the last ice age a tundra environment stretched from what is now France all the way to Canada and as far south as China. This enormous habitat included mammoths, woolly rhinoceroses, bison, reindeer, horses, elk and predators including cave lions and wolves.

The grazers ranged across this vast area basically keeping the woody vegetation down thus encouraging more grass growth and the carnivores kept the herds fit and culled. In their search for food the grazers trampled over the snow, compacting it and supporting a rising albedo.

Much changed as the last ice age came to a close 10,000 years or so ago, but a Russian team set up a research station in northeastern Siberia in 1989 with the hope that they might turn the clock back and geoengineer a habitat that would duplicate the one that supported the mammoths.

‘Rewilding’

Known as Pleistocene Park it is an attempt at "rewilding" today's tundra, bringing back as many of the old wildlife cohort as possible and then just letting nature get on with it.

There are no mammoths available any more but there are bison and horses and reindeer and also large predators. The Russians have set up a modest-sized habitat and there are ongoing efforts to achieve a balanced mammoth ecosystem and if this works they would hope to see an expansion of the park.

Oxford’s goal was to try and cost out the rewilding and they concluded that recreating the tundra ecosystem on a huge scale would be costly but economically viable.

They provided a detailed analysis for the cost of setting up three large scale trial areas and monitoring them for 10 years and estimate that the experiment annually would keep 72,000 tonnes of carbon in the ground.

The payback is even better if the price of the carbon saved is taken into account. And it could open up a new kind of tourism, the Oxford researchers suggest, offering visitors a taste of carbon-negative wild meat.

Oxford published its research on January 27th in the Philosophical Transactions of the Royal Society B. Sergey A Zimov founded the research station where he conducts his research and also Pleistocene Park