Top-down approaches

1. Approaches to city-level methodologies Top-down approaches - Top-down methods start with aggregated information and then disaggregate this down as far as they can. - Use of national datasets Bottom-up approaches - Bottom-up methods on the other hand start with disaggregated information and then aggregate this information as far as they possibly can. - Use of local datasets.

2. Approaches to city-level methodologies Top-down approaches - Construct a complete inventory of CO2 emissions from a city - Provide overall CO2 figures for various energy-related sectors. - Do not identify which parts within a particular sector are the pollution hotspots and could be targeted for future action. Bottom-up approaches - Tend to use highly-disaggregated, physically-based engineering-type models. - May require information such as thermal performance of walls, efficiency of heating systems, or the specific energy consumption of a television set. - Used to suggest likely outcomes of policies, or to identify a range of technological measures intended to improve end-use efficiencies.

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