Projects' carbon footprints are now an important impact for assessment. The common approach of comparing a project's emissions with that of the host jurisdiction and interpreting the inevitably small emission volume of the project to be of no significance is faulty logic. This minimization argument approach would be unacceptable to proponents if it was applied to project benefits. The correct approach is to adopt internationally-recognized climate change significance thresholds which lead to a conclusion that most projects would cause significant impacts and thus the issue is one of justification.