At these smaller scales, factors such as land-use change and pollution also complicate the detection of anthropogenic warming influence on physical and biological systems. {WGI 8.3, 9.4, SPM; WGII 1.4, SPM}The magnitude of CO2 emissions from land-use change and CH4 emissions from individual sources remain as key uncertainties. {WGI 2.3, 7.3, 7.4; WGIII 1.3, TS.14} [3]- Fundamental open questions