HTTP Response Header Field: Carbon-Emissions-Scope-2

Introduction The growing awareness of the environmental impact of internet usage has led to increased interest in measuring and reducing the carbon footprint of web-based services. One way to achieve this goal is to report the carbon emissions associated with the processing of HTTP requests, so that service providers and consumers can make more informed decisions about their use of the web. This document defines the "Carbon-Emissions-Scope-2" HTTP response header field , which allows servers to report the amount of carbon emissions associated with the processing of a given HTTP request, and the building of the corresponding HTTP response, as calculated according to the Scope 2 protocol outlined in . The Scope 2 protocol provides a standardized method for quantifying and reporting the greenhouse gas emissions associated with the consumption of purchased or acquired electricity, steam, and heating or cooling. By reporting the carbon emissions associated with the processing of a request, web service providers can give consumers greater visibility into the environmental impact of their service.

Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Header Field Definition The "Carbon-Emissions-Scope-2" header field is a response header field that indicates the amount of carbon emissions associated with the processing of a given HTTP request, as calculated according to the Scope 2 protocol outlined in . The value of this header field MUST be a non-negative decimal number expressed in grams of CO2-eq (carbon dioxide equivalent). A server MAY include the "Carbon-Emissions-Scope-2" header field in any response to an HTTP request. If a server includes the header field in a response, it indicates that the reported emissions are associated with the processing of the request, including any server-side processing and any use of energy by third-party services involved in serving the request. The header field MAY be included in any response status code. However, it is particularly useful in responses that include a representation of a resource, such as a web page or image, where the processing and delivery of the representation is likely to result in significant carbon emissions. The syntax of the "Carbon-Emissions-Scope-2" header field is as follows:

Syntax for the "Carbon-Emissions-Scope-2" header field. Carbon-Emissions-Scope-2 = grams-co2 grams-co2 = 1*DIGIT [ "." 1*3DIGIT ] The "grams-co2" value is the number of grams of CO2 emitted associated with the processing of the corresponding HTTP request, as calculated according to the Scope 2 protocol outlined in .

IANA Considerations This document requests the registration of the "Carbon-Emissions-Scope-2" HTTP response header field in the "Hypertext Transfer Protocol (HTTP) Response Header Fields" registry maintained by the Internet Assigned Numbers Authority (IANA). The registration template for the "Carbon-Emissions-Scope-2" header field is as follows:

Registration template for the "Carbon-Emissions-Scope-2" HTTP response header field. Header field name: Carbon-Emissions-Scope-2 Applicable protocol: http Status: standard Author/Change controller: IETF Specification document(s): This document Related information: None

Security Considerations The use of the "Carbon-Emissions-Scope-2" header field does not introduce any new security risks beyond those associated with the transmission of any HTTP response header field. However, it is important to note that the accuracy of the reported carbon emissions depends on the accuracy of the data used in the Scope 2 calculation, as well as the accuracy of any assumptions made in the calculation. As such, an attacker could potentially attempt to manipulate the reported emissions by tampering with the data or assumptions used in the calculation, or by interfering with the energy sources used by the server or third-party services involved in serving the request. To mitigate these risks, it is important for servers to use accurate data and assumptions in their Scope 2 calculations and to protect the integrity and availability of their energy sources. Additionally, it may be useful to provide transparency and verification mechanisms to ensure the accuracy of reported emissions.