State 2 ways in which atmospheric co2 can be fixed
Answers
If we have put too much CO2 into the air, wouldn’t it make sense to find ways to remove it again? Well, yes: it would. But sadly it isn’t likely to be easy or cheap and, according to new research, it isn’t an adequate “solution” to the problems of climate change.
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.
Both the UK Royal Society and the US National Research Council point out that doing it on a large enough scale to make a real difference would be hard. Nevertheless, a joint communiqué from UK learned societies recently argued that to limit global warming to 2℃ we are likely to need CO2 removal (CDR) rates in the latter part of this century that will exceed emissions at that time (“net negative emissions”). That will only be possible if we can deploy CDR technologies.
‘Negative emission’ technology comes in many forms. Caldecott et al / SSEE
A new paper in Nature Communications shows just how big the required rates of removal actually are. Even under the IPCC’s most optimistic scenario of future CO2 emission levels (RCP2.6), 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 removal could potentially help to reduce problems such as ocean acidification. So a second paper in Nature Climate Change is also discouraging because it shows that even massive and sustained carbon removal at rates of five billion tonnes a year or more would not be enough to restore anything like pre-industrial conditions in the oceans, if mitigation efforts were to be relaxed.