As the impacts of climate change become evident worldwide, organisations across all sector of the economy are actively aiming at reducing their carbon footprints. Video streaming has been in the spotlight since the beginning of the pandemic. Previous work has identified opportunities to reduce electricity consumption, yet methods to reliably estimate the carbon reduction potential from interventions on video streaming systems are currently lacking. In particular, not enough consideration is given to the consistent methodological approach to impact assessment required to adequately account for the complex interactions between changes to a service and operational and structural effects at internet-scale systems at varying time scales. In this text, we review the state of knowledge and propose a consistent short-term marginal approach for the assessment of the short-term decarbonisation potential of interventions. We illustrate this with a simplified example intervention and contrast it to previous methodologically inconsistent approaches, in which we evaluate the temporary reduction of the video spatial resolution of user-generated content video on demand from 1080p to 720p in a fixed ladder scenario over one month in the UK. We find that the carbon reductions mainly come from savings at user devices, but are overall negligible at 0.5 gCO2e per day per typical laptop-viewer.

We present the DIMPACT /dimpækt/ tool for environmental assessments of digital services. The tool enables digital media providers to calculate energy consumption and associated environmental impact across the entire product system, including datacentres, networks and user devices. It is based on accepted standard methodologies and applies state-of-the-art research. The DIMPACT tool is used by major media organisations for environmental reporting and to support development of strategies to reduce environmental impact. It has significantly advanced the knowledge of carbon emissions of video streaming. The tool is part of the wider DIMPACT project of companies that collaborate to exchange knowledge, engage suppliers and expand the scope of the tool. In this text we provide an overview of workings of tool and its methodological foundation.

We present the EAM toolkit for life cycle modelling and impact analysis in environmental assessments. The open source toolkit was specifically designed to support maintainability and verification of models within integrated assessments, and has been used in research and industry. The tool offers features to support complex Life Cycle Assessment, including dynamic and scenario modelling, uncertainty and sensitivity analysis, a flexible domain specific modelling language and a visual editor. In this introduction we present the main features of the toolkit, summarise the high-level components and illustrate its use.

Recent research has advocated for a broader conception of evaluation for Sustainable HCI (SHCI), using interdisciplinary insights and methods. In this paper, we put this into practice to conduct an evaluation of Sustainable Interaction Design (SID) of digital services. We explore how SID can contribute to corporate greenhouse gas (GHG) reduction strategies. We show how a Digital Service Provider (DSP) might incorporate SID into their design process and quantitatively evaluate a specific SID intervention by combining user analytics data with environmental life cycle assessment. We illustrate this by considering YouTube. Replacing user analytics data with aggregate estimates from publicly available sources, we estimate emissions associated with the deployment of YouTube to be approximately 10MtCO2e p.a. We estimate emissions reductions enabled through the use of an SID intervention from prior literature to be approximately 300KtCO2e p.a., and demonstrate that this is significant when considered alongside other emissions reduction interventions used by DSPs.

The use of information and communication technology and the web-based products it provides is responsible for significant emissions of greenhouse gases. In order to enable the reduction of emissions during the design of such products, it is necessary to estimate as accurately as possible their carbon impact over the entire product system. In this work we describe a new method which combines models of energy consumption during the use of digital media with models of the behavior of the audience. We apply this method to conduct an assessment of the annual carbon emissions for the product suite of a major international news organization. We then demonstrate its use for green design by evaluating the impacts of five different interventions on the product suite. We find that carbon footprint of the online newspaper amounts to approximately 7700 tCO2e per year, of which 75% are caused by the user devices. Among the evaluated scenarios a significant uptake of eReaders in favor of PCs has the greatest reduction potential. Our results also show that even a significant reduction of data volume on a web page would only result in small overall energy savings.

We present an analysis of the potential worldwide demand for downloaded data and the resulting energy requirements of the cloud. Assuming that the average westerner's media consumption moves fully online but does not rise substantially beyond current levels, and the global middle class reach western levels of consumption, we estimate the overall demand to be 3200 MB/day per person, totaling 2570 Exabytes per year by the world population. We estimate the current energy demand for bandwidth to be 4 Wh/MB, based on two independent sources of data. We conclude that the average power required to support this activity would be 1175 GW at current levels of efficiency, and that a factor 60 performance improvement would be needed if infrastructure energy is to be provided by 1% of renewable energy capacity in 2030. By looking at historical trends in energy efficiency, we observe that this would be reached around 2021 if these trends continue. We document potential new applications that might require bandwidth capacity beyond our estimate. We also outline behavior change strategies that could be used to reduce the overall demand for bandwidth if historical performance improvements are not maintained, and as interim measures prior to efficiencies being realized.

The paper reports on prototype systems to provide an infrastructure for the dynamic and flexible re-purposing of multimedia resources held in a large database. The database, called ARKive, holds film, stills, audio and text about globally endangered and native UK animal and plant species as well as their habitats. It aims to offer a wide range of users customised access to both the core multimedia data, and full integration of core data with external educational resources. Aspects covered in the paper include: designing for re-purposing with respect to specific audiences, storage and querying using RDF, XSL, SMIL and related technologies. The advantages of the approaches taken are discussed and key issues are highlighted.