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Could we ever pull enough carbon out of the atmosphere to stop climate change?

Planting 1 trillion trees is one way to store unwanted carbon.
Planting 1 trillion trees is one way to store unwanted carbon.
(Image: © Shutterstock)

Nature has equipped Earth with several giant "sponges," or carbon sinks, that can help humans battle climate change. These natural sponges, as well as human-made ones, can sop up carbon, effectively removing it from the atmosphere. 

But what does this sci-fi-like act really entail? And how much will it actually take — and cost — to make a difference and slow climate change

Sabine Fuss has been looking for these answers for the last two years. An economist in Berlin, Fuss leads a research group at the Mercator Research Institute on Global Commons and Climate Change and was part of the original Intergovernmental Panel on Climate Change (IPCC) — established by the United Nations to assess the science, risks and impacts of global warming. After the panel’s 2018 report and the new Paris Agreement goal to keep global warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius) or less, Fuss was tasked with finding out which carbon removal strategies were most promising and feasible. 

Related: What is a carbon sink?

Afforestation and reforestation — planting or replanting of forests, respectively — are well known natural carbon sinks. Vast numbers of trees can sequester the greenhouse gas carbon dioxide (CO2) from the atmosphere for photosynthesis, a chemical reaction that uses the sun's energy to turn carbon dioxide and water into sugar and oxygen. According to a 2019 study in the journal Science, planting 1 trillion trees could store about 225 billion tons (205 billion metric tons) of carbon, or about two-thirds of the carbon released by humans into the atmosphere since the Industrial Revolution began. 

Agriculture land management is another natural carbon removal approach that's relatively low risk and already being tested out, according to Jane Zelikova, terrestrial ecologist and chief scientist at Carbon180, a nonprofit that advocates for carbon removal strategies in the U.S. Practices such as rotational grazing, reduced tilling and crop rotation increase carbon intake by photosynthesis, and that carbon is eventually stored in root tissues that decompose in the soil. The National Academy of Sciences found that carbon storage in soil was enough to offset as much as 10% of U.S. annual net emissions — or about 632 million tons (574 million metric tons) of CO2 — at a low cost. 

But nature-based carbon removal, like planting and replanting forests, can conflict with other policy goals, like food production, Fuss said. Scaled up, these strategies require a lot of land, oftentimes land that's already in use. 

This is why more tech-based approaches to carbon removal are crucial, they say. With direct air capture and carbon storage, for instance, a chemical process takes carbon dioxide out of the air and binds it to filters. When the filter is heated, the CO2 can be captured and then injected underground. There are currently 15 direct air capture plants worldwide, according to the International Energy Agency. There's also bioenergy with carbon capture. With this method, plants and trees are grown, creating a carbon sink, and then the organic material is burned to produce heat or fuel known as bioenergy. During combustion, the carbon emissions are captured and stored underground. Another carbon capture trick involves mineralization; in this process, rocks get ground up to increase the surfaces available to chemically react with, and crystallize, CO2. Afterward, the mineralized CO2 is stored underground. 

However, none of these technologies have been implemented on a large scale. They're extremely expensive, with estimates as high as $400 per ton of CO2 removed, and each still requires a lot of research and support before being deployed. But the U.S. is a good example of how a mix of carbon removal solutions could work together, Zelikova said: Land management could be used in the agricultural Midwest; basalt rocks in the Pacific Northwest are great for mineralization; and the oil fields in the Southwest are already primed with the right technology and skilled workers for underground carbon storage, she said. 

Related: Why does the Earth rotate?

Ultimately, every country will have to put together its own unique portfolio of CO2 removal strategies because no single intervention will be successful on its own. "If we scaled up any of them exclusively, it would be a disaster," Fuss said. "It would use a lot of land or be prohibitively expensive." Her research has shown that afforestation and reforestation will be most productive in tropical regions, whereas solar radiation differences in the more northern latitudes with more albedo (reflection of light back into space) mean those countries will likely have better luck investing in the more technological interventions, such as carbon capture and biomass extraction.

The need to deploy these solutions is imminent. The global carbon budget, the amount of CO2 humans can emit before the global temperature rises 2.7 F (1.5 C) above preindustrial levels, is about 300 gigatons of CO2, Fuss said. 

"In recent years, we've emitted 40 gigatons," she said. Put another way, only a few years are left in that budget. A recent study in the journal Scientific Reports suggests that waiting even a few years from now may be too late if we are to meet the goal set in the Paris Agreement. Based on their climate model, the authors predict that even if we stop emitting greenhouse gases entirely, "global temperatures will be 3 C [5.4 F] warmer and sea levels 3 meters [10 feet] higher by 2500 than they were in 1850." To reverse climate change's effects, 33 gigatons of existing greenhouse gases must be removed this year and every year moving forward, the researchers said.  

The reality, however, is these approaches are not ready and there's not a consensus on how to pay for them. There is a consensus among scientists on the next step: We need to stop further emissions immediately. But, "since emissions are embedded in our daily lives and infrastructure," Fuss said, "[carbon] removal comes more to the forefront."

Originally published on Live Science.

  • Marathon
    Some of the CO2 we've put into the atmosphere has been absorbed by the oceans. If we are able to remove CO2 from the atmosphere, and do so, will the oceans release excess CO2?

    If the oceans do release their excess CO2, it will increase the amount of CO2 we need to remove from the atmosphere. Will it also help raise the ocean's pH?
    Reply
  • mitomke
    Its not the carbon in the air that warms the sea surface temperature. It's the long chain carbon in the water (Turbidity) and the Heat in the water in streams going into the estuaries, wetlands and coastal waters. This leads to the creation of Anoxic zones. Heterotrophic bacteria decomposing the dirty warm water take oxygen out and respire carbon dioxide. Water holds a thousand times more Heat than Air. So lets think with Common sense in Science.
    Reply
  • Finch
    admin said:
    Can we harness natural and human-made carbon traps to help us slow climate change?

    Could we ever pull enough carbon out of the atmosphere to stop climate change? : Read more
    What was putting Carbon into the atmosphere 20,000 years ago when the current warming trend began.
    Reply
  • FB36
    Also, IMHO, Global Warming problem is already getting solved by humanity using solar & wind (& nuclear) power more & more & there are large scale tree planting campaigns getting done!
    Right/best way to store CO2 is by planting trees!!! (NOT insanely dangerous geoengineering!)
    If Earth's forests were not greatly destroyed since beginning of industrial age, would there be a GW problem today, regardless of how much fossil fuel usage? Please research/simulate/calculate that!!

    Also, IMHO, storing CO2 in old natural gas wells maybe OK, but using it for fracking is extremely dangerous!
    Crashing/filling deep rocks under our feet using a gas is even more dangerous than doing fracking using water!
    Both needs to be banned ASAP unless we want to see much bigger earthquakes & maybe even worse like ground collapse event(s)!!!
    Reply
  • Chem721
    Marathon said:
    Some of the CO2 we've put into the atmosphere has been absorbed by the oceans. If we are able to remove CO2 from the atmosphere, and do so, will the oceans release excess CO2?

    Yes, the oceans will yield up CO2 if we start removing it. As CO2, it is a gas, and can dissolve into water to produce carbonic acid. Since the oceans are slightly basic (pH ca. 8.2), they can absorb a lot more CO2 than fresh water, which is typically near neutral (pH 7).

    Formation of carbonic acid is shown as CO2 + H20 -> H2CO3 -> H+ + HCO3-. The proton from carbonic acid then drives pH down in the oceans. As long as the atmospheric CO2 is high, the carbonic acid formation will remain high, driving down the pH, which ultimately will cause problems for many species.

    However, the above reactions are reversible, and the dominant form in the oceans depend on the amount of CO2 in the atmosphere. As you delete it from the air, the reaction shifts to the left, favoring formation of CO2. Since CO2 can out-gas from the water to increase pH to where we want it, removal of CO2 will reverse this trend.

    But the problem is more dire than many realize. It is not just carbon generated by humans, but the warming planet has begun to release carbon from other sources. As the article in Nature below indicates, we probably need a miraculous invention for direct air capture and develop a means of sequestering the CO2. It does not appear there is sufficient land mass to grow enough biomass to compensate for the ever-increasing CO2 loading.


    "Permafrost collapse is accelerating carbon release"

    1. https://www.nature.com/articles/d41586-019-01313-4
    Reply
  • Finch
    Chem721 said:
    Yes, the oceans will yield up CO2 if we start removing it. As CO2, it is a gas, and can dissolve into water to produce carbonic acid. Since the oceans are slightly basic (pH ca. 8.2), they can absorb a lot more CO2 than fresh water, which is typically near neutral (pH 7).

    Formation of carbonic acid is shown as CO2 + H20 -> H2CO3 -> H+ + HCO3-. The proton from carbonic acid then drives pH down in the oceans. As long as the atmospheric CO2 is high, the carbonic acid formation will remain high, driving down the pH, which ultimately will cause problems for many species.

    However, the above reactions are reversible, and the dominant form in the oceans depend on the amount of CO2 in the atmosphere. As you delete it from the air, the reaction shifts to the left, favoring formation of CO2. Since CO2 can out-gas from the water to increase pH to where we want it, removal of CO2 will reverse this trend.

    But the problem is more dire than many realize. It is not just carbon generated by humans, but the warming planet has begun to release carbon from other sources. As the article in Nature below indicates, we probably need a miraculous invention for direct air capture and develop a means of sequestering the CO2. It does not appear there is sufficient land mass to grow enough biomass to compensate for the ever-increasing CO2 loading.


    "Permafrost collapse is accelerating carbon release"

    1. https://www.nature.com/articles/d41586-019-01313-4
    Total nonsense, because the current warming trend began at the ebb of the last ice age which was over 20,000 years ago. How did my car or my fathers or grandfathers car start that warming

    But you believe everything you hear and see on TV, you always did and will
    Reply
  • Chem721
    Marathon said:
    If the oceans do release their excess CO2, it will increase the amount of CO2 we need to remove from the atmosphere. Will it also help raise the ocean's pH?

    So yes, removing CO2 from the atmosphere would out-gas dissolved CO2 in the oceans, driving up pH. And yes it will increase the amount of CO2 we need to remove from the atmosphere.

    It is basically a balancing act between the existing pH of the oceans and how much CO2 is in the atmosphere. The more CO2, the more acidic the oceans. The more acidic the oceans, the more stressed the food chain, etc.
    Reply
  • Finch
    Chem721 said:
    So yes, removing CO2 from the atmosphere would out-gas dissolved CO2 in the oceans, driving up pH. And yes it will increase the amount of CO2 we need to remove from the atmosphere.

    It is basically a balancing act between the existing pH of the oceans and how much CO2 is in the atmosphere. The more CO2, the more acidic the oceans. The more acidic the oceans, the more stressed the food chain, etc.
    LOL so if we reduce CO2 in the atmosphere then the oceans start polluting the air.

    Wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

    Not everything on TV is real

    Really
    Reply
  • CrisS
    The article is missing the whole ocean reef carbon sink (and without acidifying the oceans). There's some students who have figured out a way to build (restore) reefs at an extremely rapid rate versus letting nature take its course (I wish I had the link to their research--if I find it I'll post it). As long as the right locations are found (so it doesn't interfere with shipping channels) you could build reefs in addition to forestation (and apparently the baggage this article says that brings with it). Scuba divers such as myself would love it. Additionally, you can populate the reefs with the plant species that aren't heat sensitive so they are more tolerant than most of the reefs now. I'm much more of a fan of helping nature restore itself and managing to correct for how we disturb nature.
    Reply
  • Aaron80
    What would it take to remove 500 billion tons of carbon dioxide from our shared atmosphere and oceans in the next 100 years? If all our medium sized global cities built Tesla Giga factory sized Giga farms could we reverse our carbon emissions enough to reverse climate change?

    These gigantic renewably powered buildings could be profitable by growing and selling food to their nearby cities in one half. In the other half these buildings could grow high carbon sequestering biology making biochar for biomass extraction and then geologic burial rebuilding our coal mines, oilfields and global soils thus removing industrial carbon emissions.

    What is the highest carbon sequestering and fast growing biology? How much carbon could each Giga farm sequester annually? How many Giga farms would we need to reverse climate change to safe and healthy levels of carbon, say 270 ppm, (now 414 ppm) over the next 100 years?
    Reply