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JGCRI / gcam-core

GCAM -- The Global Change Analysis Model
http://jgcri.github.io/gcam-doc/
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Discrepancy between Emissions Queries and the Set Net-Zero Target #423

Open Kasra9494 opened 2 months ago

Kasra9494 commented 2 months ago

Hi all,

I'm using a customized version of GCAM V5.4, where additional CDR methods are added, to run a few net-zero scenarios for Canada. My scenario design excludes emissions from land-use and non-CO2 GHGs. The goal is for CO2 emissions to decline to net-zero by 2050 and remain there for the rest of the century. I set a target of -0.1 MtC, understanding that it's sometimes better not to use overly precise values.

However, when I check the results using the model interface, I notice a discrepancy. The "CO2 emissions by region" query aligns with my target, but when I run the "CO2 emissions by sector" or "CO2 emissions by sector (No bio)" queries and sum their rows, they differ from the "CO2 emissions by region" query and my target. As shown in the figure below, the orange line stays at 0, but the overlapping green lines dip into negative territory toward the end, and they don't match in the initial years either.

Can anyone help me resolve this issue?

Thanks, Kasra Motlaghzadeh Emissions Charts

pkyle commented 2 months ago

The CO2 emissions by sector query is only reporting emissions from sectors, so it misses any emissions from primary energy resource production, which includes fugitive CO2 from oil and gas production (venting of CO2, flaring of associated natural gas), and in Canada probably also includes the energy use in oil sands production. CO2 emissions by region is more comprehensive. You can confirm that this is the source of the difference by querying CO2 emissions by resource production I don't know why the (No Bio) one goes negative towards the end of the century, but I don't recommend using that query for reporting whole-region emissions, because the additional calculations that it's doing, to assign the negative emissions of biomass production to the sectors that use the biomass and derived fuels, aren't being used anyway when all sectors are being added up.

Kasra9494 commented 1 month ago

Thank you so much @pkyle. You are right. The difference is basically equal to the CO2 emissions by resource production. I'm very grateful for the help.