To understand this, we need to remember that to meet the Paris Agreement target to keep global warming \u201cwell below 2\u00b0C\u201d, the world has less than 12 years<\/a> of current CO\u2082 emissions<\/a> until it exhausts its remaining budget. It is now becoming clear that the only way to stay within this budget is to capture and store massive amounts of CO\u2082<\/a>.<\/p>\n What is usually overlooked though is that since the beginning of industrialization, most of the CO\u2082 emitted (57%)<\/a> has been taken up by natural processes. In fact, while emissions from fossil fuels, cement production and deforestation have been growing exponentially (at 1.65% per year since 1850<\/a>), my own research has found that natural sinks on land and in the ocean have been almost exactly keeping up with the growth<\/a>.<\/p>\n Processes on land alone are responsible for taking up about a third of human CO\u2082 emissions. So for every kilo of carbon emitted by a car or a power plant, about 350 grams will end up in a tree trunk, a leaf, or decomposed into the soil. There is no consensus about exactly what is responsible for the growing strength of the land sink, but most likely it is a combination of more CO\u2082 in the atmosphere and nitrogen-containing chemicals from agriculture and industry ending up on soils and leaves, both of which make plants grow faster, as well as forests regrowing when agricultural lands are abandoned.<\/p>\n The inclusion of a constant EU-wide carbon sink calculated following the EU\u2019s own rules effectively lowers the promised fossil-fuel reduction from 55% to somewhere between 53% and 50%<\/a>.<\/p>\n But there is a much more fundamental problem with the Commission\u2019s approach. It is a subtle form of double accounting that sets a precedent for more significant accounting tricks further down the line \u2013 or by other countries with larger land carbon sinks.<\/p>\n The problem is that when scientists calculated how much CO\u2082 we can emit and still keep within the safe limits of the Paris Agreement, nature\u2019s free carbon sucking service was already included. The net-zero goal is strictly in addition to that. By the time we hit net zero, we actually need those natural sinks to continue functioning, taking up over 22 billion tonnes of CO\u2082 per year<\/a> and continuing to reduce CO\u2082 levels in the atmosphere below where they ended up at the net-zero point. Because current levels of atmospheric CO\u2082 are not safe<\/a>. In other words, the needed net zero really is a \u201cbig minus\u201d.<\/p>\n How much carbon is stored in EU countries through natural processes is essentially unknown. Estimates<\/a> vary between 0.6 and 1.7 gigatonnes of CO\u2082 per year, with no consensus about how much of it is within EU boundaries. Contrary to the global land sink, which can be inferred from combining CO\u2082 and oxygen measurements<\/a>, the European sink cannot be measured directly because these gases mix too quickly in the atmosphere.<\/p>\n But what happens if, at some point in future, the EU produces data that shows its carbon sink has increased? The amount of fossil fuels it would be legally-required to cut would be reduced \u2013 but the scientifically-determined global carbon budget to meet the Paris Agreement would remain unchanged. Given what we know about the global land carbon sink, it is likely the EU carbon sink will approximately double between 1990 and 2030.<\/p>\n This is clearly a bad start on the road to net zero as it sets a precedent for double accounting. A possible solution might be to only account for sinks that are genuinely additional, such as planting more trees or no-till farming to increase soil carbon<\/a>. However there is still no consensus about which processes govern the natural carbon sink, and it is likely to be partly human-induced. It is therefore next to impossible to reliably determine how much of a sink is truly additional.<\/p>\n Another solution could be to allow only direct CO\u2082 uptake by human activities to be counted as \u201cremoval\u201d. So-called bioenergy with carbon capture and storage (BECCS) is one option, however it interferes with the biosphere\u2019s capacity to soak up CO\u2082 as it requires vast amounts of land<\/a> to grow biofuel crops (and competes with food production). The other option is to directly capture carbon from the air, but for now this has limited realistic potential<\/a>.<\/p>\n By far the most scientific, ethical and sensible approach would be to concentrate on emissions reductions and leave the terrestrial biosphere as intact as possible to carry on removing carbon. This free service, after all, is worth at least US$1.3 trillion per year (at a price of 100 US$\/tonne<\/a>). Natural habitats should be restored for that purpose, but the resulting carbon sink should not enter territorial accounting schemes for two reasons: because it has already been counted, and because we have no way of reliably quantifying how much is down to human policy and how much is just the natural background rate. This article is republished from The Conversation<\/a> by Wolfgang Knorr<\/a>, Senior Research Scientist, Physical Geography and Ecosystem Science, Lund University<\/a> under a Creative Commons license. Read the original article<\/a>.<\/em><\/p>\n Read next:<\/b> If you need a VPN (and you do), these five top-tier options are on sale now <\/a>\n<\/p>\n![\"Sunlight](\"https:\/\/images.theconversation.com\/files\/360550\/original\/file-20200929-24-wo7tai.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip\")
<\/a>A subtle form of double accounting<\/h2>\n
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