airmosaic-ai

GCAM-China vs Official GCAM-Core

Understanding the differences between GCAM-China (umd-cgs/gcam-china) and official GCAM-Core (JGCRI/gcam-core) before writing queries or interpreting output.

Structural Differences

GCAM-China extends official GCAM-Core with:

1. Province-level disaggregation: China is modeled as 31 provincial regions plus a national aggregate node, rather than a single “China” region.
2. Additional sectors: GCAM-China adds independent sectors that do not exist in official core (e.g., coke as a standalone supply sector).
3. Modified sector configurations: Some sectors that exist in both versions have different metadata in GCAM-China.

Sector Differences: Concrete Examples

Coke

• GCAM-Core: Coke does NOT exist as an independent supplysector=coke. In A323.sector.csv, only iron and steel is present.
• GCAM-China: Coke is an independent sector. In A323.sector_China.csv, coke appears with output-unit=Mt, price-unit=1975$/GJ.

Iron and Steel

• GCAM-Core A323.sector.csv: iron and steel, Mt, EJ, 1975$/kg, -3, industry
• GCAM-China A323.sector_China.csv: iron and steel, Mt, EJ or Mt, 1975$/GJ, 0

The price unit differs: 1975$/kg in core vs 1975$/GJ in China. This means sector cost and physical output cannot be directly multiplied to get a monetary proxy in GCAM-China without unit conversion.

Cement

• GCAM-Core: cement, Mt, EJ, 1975$/kg
• GCAM-China: Same as core for cement (no override in sector_China.csv)

Ammonia / N fertilizer

• GCAM-China uses ammonia as the internal sector name for what is conceptually the fertilizer production sector.
• The R constant gcamchina.FERT_NAME <- "ammonia" confirms this mapping.
• Some CCS-related XML files reference N fertilizer instead of ammonia, which causes initialization failures when loaded directly.

File Location Differences

File	GCAM-Core Path	GCAM-China Path
Sector catalog	energy/A323.sector.csv	gcam-china/A323.sector_China.csv
Technology costs	energy/A323.globaltech_cost.csv	gcam-china/A323.globaltech_cost.csv
Detailed industry XML	N/A (no province detail)	detailed_industry_CHINA.xml
CCS share weights	N/A	CCS_shrwt_CHINA.xml

When to Check Which Source

• Writing extraction queries for GCAM-China output: Always check GCAM-China input files and generated XML, not GCAM-Core defaults.
• Understanding a sector’s conceptual role: GCAM-Core documentation and source code can be helpful for understanding model logic.
• Comparing results between versions: Use official documentation at https://jgcri.github.io/gcam-doc/ for core definitions.

Key Reference

• GCAM-China GitHub: https://github.com/umd-cgs/gcam-china (branch gcam-china-v8)
• GCAM-Core GitHub: https://github.com/JGCRI/gcam-core
• GCAM Documentation: https://jgcri.github.io/gcam-doc/

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