The IPCC did not do primary research. They cite a source. That source did not do primary research, either. The actual data comes from an estimate from the indus

The IPCC did not do primary research. They cite a source. That source did not do primary research, either. The actual data comes from an estimate from the industry itself. The estimates came from costs. Estimating embodied fossil fuel energy based on cost is a not a bad estimation technique except when a huge amount of your supply chain is subsidized.