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CO2 removal cannot save the oceans from acidification. Traumatizing upheaval to plankton predicted.

Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities and it is responsible for increased temperatures of ocean water as well as ocean acidification.  The world’s oceans absorb huge amounts of carbon dioxide, and stores it deep in the ocean, where it’s out of the atmospheric carbon cycle for thousands of years. Over 30 % of human made carbon burned since the industrial revolution has been stored by the worlds oceans. As the oceans absorb the huge amounts of carbon that we produce, the acidity of sea water has increased, a phenomenon that is known as ocean carbonic acidification.

The European Project on Ocean Acidification

It should be noted that increasing sea water acidity lowers the ocean’s natural ‘basic’ or ‘alkaline’ status and unnaturally forces the acid base balance of sea water towards acid. If this accelerates for the next four decades as forecasted, the consequential increase in ocean acidity will be greater than anything experienced in the past 21 million years. Future projections show that by 2060, seawater acidity could have increased by 120%. To the best of our knowledge, the current rate of change is many times faster than anything previously experienced in the last 55 million years.

Microscopic marine plants known as Phytoplankton, form the foundation of the marine food web. In a balanced ecosystem, phytoplankton provide food for a wide range of sea creatures, including whales, shrimp, snails and jellyfish. Being sunlight dependent, they live near the surface allowing photosynthesis to occur. These tiny creatures supply half of the planet's oxygen as much per year as all the land plants combined. They account for 98 percent of the ocean's biomass and they were the only life form on Earth for the first 2 billion to 3 billion years. Because they take up carbon dioxide from the atmosphere, when they die they sink and carry  atmospheric carbon to the deep sea, making phytoplankton an important actor in the climate system.

In the journal Nature Climate Change, researchers report that increased ocean acidification by 2100 will spur a range of responses in phytoplankton: Some species will die out, while others will flourish, changing the balance of plankton species around the world.  

MIT News explains that even a slight advantage in more acidic waters could allow some species to outcompete and wipe out entire other species, disrupting the current balance of phytoplankton.

After running the global simulation several times with different combinations of responses for the 96 species, the researchers observed that as ocean acidification prompted some species to grow faster, and others slower, it also changed the natural competition between species.

“Normally, over evolutionary time, things come to a stable point where multiple species can live together,” Dutkiewicz says. “But if one of them gets a boost, even though the other might get a boost, but not as big, it might get outcompeted. So you might get whole species just disappearing because responses are slightly different.”

Dutkiewicz says shifting competition at the plankton level may have big ramifications further up in the food chain.

“Generally, a polar bear eats things that start feeding on a diatom, and is probably not fed by something that feeds on Prochlorococcus, for example,” Dutkiewicz says. “The whole food chain is going to be different.”

By 2100, the local composition of the oceans may also look very different due to warming water: The model predicts that many phytoplankton species will move toward the poles. That means that in New England, for instance, marine communities may look very different in the next century.

“If you went to Boston Harbor and pulled up a cup of water and looked under a microscope, you’d see very different species later on,” Dutkiewicz says. “By 2100, you’d see ones that were living maybe closer to North Carolina now, up near Boston.”

 

This US firm plans to capture carbon dioxide directly from the atmosphere. Credit: Carbon Engineering

 

 

Phys.org reports on carbon capture and sequestration which is the process of stripping carbon dioxide from fossil fuels after they are burned.

 The possible "carbon removal" techniques are very diverse. They include growing trees on land or algae in the sea and capturing and burying some of the carbon they have taken from the atmosphere. There are also engineered solutions that "scrub" CO2 directly from the air, using chemical absorbents, and then recover, purify, compress and liquefy it, so that it can be buried deep underground. That sounds difficult and expensive, and at the moment, it is.    

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A new paper in Nature Communicationsshows just how big the required rates of removal actually are. Even under the IPCC's most optimistic scenario of future CO2 emission levels in order to keep temperature rises below 2℃ we would have to remove from the atmosphere at least a few billion tons of carbon per year and maybe ten billion or more – depending on how well conventional mitigation goes.

We currently emit around eight billion tonnes of carbon per year, so the scale of the enterprise is massive: it's comparable to the present global scale of mining and burning fossil fuels.

Carbon capture is estimated to cost $17.6 trillion. The IEA calculates there should be about 1,500 full-scale CCS (CARBON CAPTURE & SEQUESTRATION) plants in operation by 2035 in order to keep the international target of limiting temperature rise to 2℃. Currently, there are just eight. CCS makes electricity more expensive. Extra fuel needs to be burned to drive the process of capturing CO2 from the power station's flue gas, and to pump it down to its resting place in rock deep underground according to BBC News. Even if carbon capture technology becomes available immediately, and it won’t, the oceans would not benefit.

Potsdam Institute for Climate Impact Research reports on their grim findings for the world’s oceans.

“Geoengineering measures are currently being debated as a kind of last resort to avoid dangerous climate change – either in the case that policymakers find no agreement to cut CO2 emissions, or to delay the transformation of our energy systems,” says lead-author Sabine Mathesius from GEOMAR Helmholtz Centre for Ocean Research Kiel and the Potsdam Institute for Climate Impact Research (PIK). “However, looking at the oceans we see that this approach carries great risks.” In scenarios of timely emissions reductions, artificially removing CO2 can complement efforts. “Yet in a business-as-usual scenario of unabated emissions, even if the CO2 in the atmosphere would later on be reduced to the preindustrial concentration, the acidity in the oceans could still be more than four times higher than the preindustrial level,” says Mathesius. “It would take many centuries to get back into balance with the atmosphere.”  

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“We did a computer experiment and simulated different rates of CO2 extraction from the atmosphere – one reasonable one, but also a probably unfeasible one of more than 90 billion tons per year, which is more than two times today’s yearly emissions,” says co-author Ken Caldeira of the Carnegie Institution for Science in Stanford, USA, who worked on this issue during a research stay at PIK. The experiment does not account for the availability of technologies for extraction and storage. “Interestingly, it turns out that after business as usual until 2150, even taking such enormous amounts of CO2 from the atmosphere wouldn't help the deep ocean that much – after the acidified water has been transported by large-scale ocean circulation to great depths, it is out of reach for many centuries, no matter how much CO2 is removed from the atmosphere.”

The scientists also studied the increase of temperatures and the decrease of dissolved oxygen in the sea. Oxygen is vital of course for many creatures. The warming for instance reduces ocean circulation, harming nutrient transport. Together with acidification, these changes put heavy pressure on marine life. Earlier in Earth’s history, such changes have led to mass extinctions. However, the combined effect of all three factors has not yet been fully understood.

 

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