Can someone explain why the LCIA, ei- IPCC 2013 and the openLCA version IPCC 2013 (CO2-uptake) have different results?

Question

Why do they have different results?

Including carbon uptake in the result it is clear to get to different results. But when I sum up only the categories, (GWP biogenic, Fossil and Land use change) shouldnt the openLCA IA-method have the same result as ei-IPCC 2013? The results differ 10%.

Comments

Please, can you give more details?

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In which way more details?
If you analyse one and the same product system e.g. Paper and you choose one time ei-IPCC 2013 and one time IPCC 2013 (CO2-uptake) they have different results.  I thought they should only differ in the category CO2-uptake.  If you sum up the results with the LCIA IPCC 2013 (CO2-uptake) but without the CO2-uptake it should have the same result as IPCC 2013 (which is by default without CO2-uptake). But the results differ.

is it more clear now?
thank you!