Top-down and bottom-up approaches to estimating city-level CO2 emissions have complementary strengths and weaknesses. Top-down approaches use aggregated national data to provide overall emission figures for sectors but cannot identify specific pollution hotspots. Bottom-up approaches use highly disaggregated local data in engineering models to suggest outcomes of policies and efficiency measures, but require detailed equipment-level information. An ideal approach for cities would combine top-down and bottom-up methods to establish baselines, forecast reductions, and inform targeted actions.

3. In conclusion Top down approaches Are they complementary to each other? What do we need to adopt for cities to be able to estimate baseline emissions, predict potential emission reductions, and take action? Bottom-up models