4． 碳足跡，即carbon footprint。簡單地說，碳足跡是用來衡量我們在日常生活中消耗的二氧化碳的一種方式。無論是開車上班、乘飛機旅行，還是使用電燈、電腦，我們都消耗石油、煤和天然氣等化石燃料。這些化石燃料在燃燒時，會排放出諸如二氧化碳之類導致地球變暖的溫室氣體。對于carbon footprint，維基百科有如下定義：A carbon footprint is "the total set of greenhouse gas (GHG) emissions caused by an organization, event or product". For simplicity of reporting, it is often expressed in terms of the amount of carbon dioxide, or its equivalent of other GHGs, emitted. 相關表達見如下例句：A new purpose-built office complex that will offer eco-friendly accommodation across 66,250 square feet is under construction in Wales. It is reported that the Cardiff Waterside project, entitled 3 Assembly Square, forms part of a £140 million construction project and will aim to offer business in the area an environment that has a lower carbon footprint than traditional office space. 上述句子的背景是，英國政府成立了一個The Low Carbon Building Programme (LCBP)，即低碳建筑計劃，維基百科解釋說，

LCBP is a Government programme in the United Kingdom administered by BERR (formerly the DTI). It offers grants towards the cost of installing domestic microgeneration technologies and larger scale distributed generation installations for public buildings and businesses, provided energy conservation standards are also met.