Accurately identifying low-carbon jobs is central to understanding the labour market impacts of the low-carbon transition. We develop a novel methodology to identify low-carbon jobs using the near universe of online job postings between 2010-2019 in the US. The share of low-carbon ads in the US economy has been constant around 1.3%, but is growing slightly in low-skilled occupations. We compare low-carbon to other job ads within narrow occupational groups and show that the green skill gaps are larger and broader than previously considered. Emphasis on technical and managerial skills is a distinguishing characteristic of all low-carbon job ads, but skill requirements are higher in general, including in cognitive and IT skills that are also important for the digital transformation. Low-carbon job ads pay a significant wage premium, but such premium declined over time.