# Bottom-up calculations

## This article covers the question of what bottom-up calculation is in ClimateOS and how it differs from other approaches.

### What is bottom-up calculation?

In ClimateOS we’re calculating your emissions based on the socio-economic activities that happen in your city (e.g. transporting people and goods from A to B) and the mechanisms those activities are carried out with. The activities are measured in terms of their operations (km driven, m2 heated, etc.) breaking the activities down to a very tangible and comprehensible level. The operations are then multiplied by the amount of energy needed to carry them out which we call energy intensities (kWh/km, kWh per m2, etc.). This multiplied by the particular emission factor results in the emission generated from the activity. This is what we call the Carbon Causal Chains (CCCs)

Building your emission inventory with CCCs is key to working with ClimateOS. That’s why all parts of the CCCs are fully editable. To give you the freedom to choose which scopes of emissions you want to take responsibility for. ClimateOS gives you full control over your data and therefore emissions. Thus, the emissions of your city are calculated from the bottom-up, from the socioeconomic activities happening in your city.

### How does this differ from other approaches?

Instead of entering emissions data from an external source, the approach in ClimateOS is to first describe the activities and their operations, and then use other parameters to calculate the resulting emissions in your inventory. This approach lies at the heart of all the calculations in ClimateOS, and is essential when we move away from the inventory to the next steps in your Transition, i.e. exploring how to reduce the emissions in each of the Carbon Causal Chains (CCCs).

The key here is not to rely on fixed arbitrary (top-down) reductions, whether absolute or proportional, in emissions, but to be able to calculate, from the bottom-up, what the future activities and operations are, with the resources used, to have an accurate picture of the resulting emissions.

Everything else you’re using ClimateOS for (setting your targets, balancing your targets against each other, ROI, etc.) is based on the data you’re inputting, the very foundation of your climate transition.

An example of bottom-up calculations in practice can be seen by looking at the Transition element for shifting to public transport. The aim of the Transition elements is to shift the high carbon activities to low carbon activities. This Target models the shift of commutes from cars to public transport. Having established how many kilometres are driven by fossil fuelled cars as well as the average load factor for cars and buses through the input data, the shift modelled becomes very comprehensible.