Life Cycle Assessment (LCA) is increasingly used to quantify and regulate the environmental impacts of Information and Communication Technology (ICT) systems. Since direct biosphere measurements are complicated to perform, we claim that the environmental impact assessment of ICT relies heavily on models. In this paper, we first revisit the fundamentals of LCA: we emphasize that ICT LCAs effectively form systems of models, and we argue that such systems require an extra-high level of carefulness in construction, calibration, integration, and interpretation. We then document how this level of rigor is challenging to achieve with current practices. This is illustrated with emblematic examples of model misuse and an analysis of structural challenges related to database choice, scope mismatches, opaque aggregation, and model integration. From this analysis, we derive four key requirements for credible ICT LCA: explicit model lineage, clearly defined model scope, end-to-end traceability, and managed non-obsolescence. Finally, we propose a framework that operationalizes these requirements using explicit dependency graphs, an open and versioned LCA-oriented model repository, automatic enforcement of integrity constraints, and a well-defined model taxonomy.

翻译：生命周期评估（LCA）正越来越多地被用于量化与调控信息通信技术（ICT）系统的环境影响。由于直接进行生物圈测量操作复杂，我们认为ICT的环境影响评估高度依赖模型。本文首先重新审视了LCA的基本原理：我们强调ICT的LCA本质上是模型系统的组合，并论证这类系统在构建、校准、集成与解读过程中需要格外审慎。随后我们通过典型模型误用案例，以及数据库选择、范围错配、不透明聚合和模型集成等结构性挑战的分析，揭示了当前实践难以达到这种严谨性要求。基于此分析，我们提炼出可信赖ICT LCA的四个关键要求：明确的模型谱系、清晰定义的模型范围、端到端可追溯性，以及受控的非过时性。最后，我们提出一个框架，通过显式依赖图、面向LCA的开放版本化模型库、自动完整性约束强制执行以及明确定义的模型分类法，将这些要求付诸实践。