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Avoid restricting the SCI by prescribing a specific metric. #353

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Avoid restricting the SCI by prescribing a specific metric. #353

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3752611
Remove “marginal” due to lack of scientific consensus. Add hourly gra…
ciril-emaps Feb 14, 2023
a7cf41d
Remove marginal and with it the explanation. Add hourly granularity.
ciril-emaps Feb 14, 2023
ef069dc
Remove “marginal” due to lack of scientific consensus, to allow for d…
ciril-emaps Feb 14, 2023
4f3e817
Remove consequential. Many formulations in SCI are attributional. Con…
ciril-emaps Feb 14, 2023
8a3eadc
Remove “marginal” due to lack of scientific consensus, to allow for d…
ciril-emaps Feb 14, 2023
6309950
Remove paragraph to reflect removal of marginal.
ciril-emaps Feb 14, 2023
28a4d92
Add “verifiable”. Impact of actions need to be verifiable to be credi…
ciril-emaps Feb 14, 2023
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14 changes: 6 additions & 8 deletions Software_Carbon_Intensity/Software_Carbon_Intensity_Specification.md
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Expand Up @@ -46,7 +46,7 @@ attribute of software or hardware that adjusts its behavior (consumption of inpu

The following abbreviations are used throughout this specification:
- E – Energy consumed by a software system
- I – Location-based marginal carbon intensity
- I – Hourly location-based carbon intensity
- M – Embodied emissions of the hardware needed to operate a software system
- O – Operational emissions based on the emissions caused by energy consumption
- R – Functional unit
Expand Down Expand Up @@ -96,7 +96,7 @@ This can be expanded to:

#### General

To calculate the operational emissions associated with software, multiply the electricity consumption of the hardware the software is running on by the regional, granular marginal emissions rate. The marginal emissions rate reflects the change in emissions associated with a change in demand.
To calculate the operational emissions associated with software, multiply the electricity consumption of the hardware the software is running on by the regional, hourly emissions rate.

To calculate the operational emissions `O` for a software application, use the following:

Expand All @@ -115,13 +115,11 @@ Units: this shall be in kilowatt hours (kWh).

The energy consumption should include all energy consumed by hardware reserved or provisioned, not just the hardware actually used to meet the software needs.

#### Location-based marginal carbon intensity
#### Location-based carbon intensity

The carbon intensity of electricity is a measure of how much carbon (CO2eq) emissions are produced per kilowatt-hour (kWh) of electricity consumed. Because this specification uses a consequential approach, marginal emissions rates shall be used for electricity consumption.
The carbon intensity of electricity is a measure of how much carbon (CO2eq) emissions are produced per kilowatt-hour (kWh) of electricity consumed.

Location-based marginal emissions factors measure the grid carbon intensity of a grid region. If the electricity consumption is connected to a grid, the marginal emissions rate of that grid shall be used, which excludes any [market-based measures](#market-based-measures). If the electricity consumption is not connected to a larger regional grid, an appropriate emissions factor for that system shall be used. From a developer perspective, only the location-based info is important in terms of the impact on eliminating carbon emissions. This excludes [market-based measures](#market-based-measures) and is distinct from 100% renewable energy claims.

The only figure that matters when trying to optimize the scheduling of a computation in real-time is the marginal emissions intensity. This is the emissions intensity of the marginal power plant which will need to be turned up if a computation is scheduled (e.g., increase electricity demand from the grid) at that moment.
Location-based emissions factors measure the grid carbon intensity of a grid region. If the electricity consumption is connected to a grid, the emissions rate of that grid shall be used, which excludes any [market-based measures](#market-based-measures). If the electricity consumption is not connected to a larger regional grid, an appropriate emissions factor for that system shall be used. From a developer perspective, only the location-based info is important in terms of the impact on eliminating carbon emissions. This excludes [market-based measures](#market-based-measures) and is distinct from 100% renewable energy claims.

Units: this shall be in grams of carbon per kilowatt hours (gCO2eq/kWh).

Expand Down Expand Up @@ -257,7 +255,7 @@ As this specification develops, the following core characteristics shall remain

- **The SCI is sensitive to carbon awareness, energy efficiency, and hardware efficiency**
- The purpose of the SCI is to encourage actions that reduce the carbon emissions of software. Therefore, the SCI shall be sensitive to those actions described in this document under **Software Sustainability Actions**; specifically, carbon awareness, energy efficiency, and hardware efficiency.
- If an application's SCI is X, and then actions are taken to make the application more carbon aware, more energy efficient, or more hardware efficient, the value of X shall go down.
- If an application's SCI is X, and then actions are taken to make the application verifiably more carbon aware, more energy efficient, or more hardware efficient, the value of X shall go down.

- **The SCI takes a systems-impact view**
- The purpose of the SCI is to encourage actions that reduce carbon emissions of software in a way that creates reductions at a system-wide level rather than just at a local level. Local-level optimizations may lead to micro improvements but may have negative downstream impacts at a macro level that negate the impact of those actions.
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