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Quality of geological CO2 storage to avoid jeopardizing climate targets

Asbjørn Torvanger, Alv-Arne Grimstad, Erik Gøsta Brun Lindeberg, Nathan Appleton Rive, Kristin Rypdal, Ragnhild Bieltvedt Skeie, Jan S. Fuglestvedt, Petter Tollefsen

We explore allowable leakage for carbon capture and geological storage to be consistent with maximum global warming targets of 2.5 and 3°C by 2100. Given plausible fossil fuel use and carbon capture and storage scenarios, and based on modeling of time-dependent leakage of CO2, we employ a climate model to calculate the long-term temperature response of CO2 emissions. We assume that half of the stored CO2 is permanently trapped by fast mechanisms. If 40 % of global CO2 emissions are stored in the second half of this century, the temperature effect of escaped CO2 is too small to compromise a 2.5°C target. If 80 % of CO2 is captured, escaped CO2 must peak 300 years or later for consistency with this climate target. Due to much more CO2 stored for the 3 than the 2.5°C target, quality of storage becomes more important. Thus for the 3°C target escaped CO2 must peak 400 years or later in the 40 % scenario, and 3000 years or later in the 80 % scenario. Consequently CO2 escaped from geological storage can compromise the less stringent 3°C target in the long-run if most of global CO2 emissions have been stored. If less CO2 is stored only a very high escape scenario can compromise the more stringent 2.5°C target. For the two remaining combinations of storage scenarios and climate targets, leakage must be high to compromise these climate targets.

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