The chart below represents country-level estimates of carbon intensity for all major oil and gas producing countries, that is to say emissions expressed as CO2 equivalence from fossil fuel production in addition to emissions from burning fossil fuels from energy used in operations, carbon dioxide and methane venting, flaring, fugitive methane emissions, transport and refining.

These emissions factors are embedded in the estimates made by the Global Registry. The analysis is based on three datasets published by the International Energy Agency, and one by Opgee, a research unit based in Stanford University.

In seeking to cover the entire supply chain, the Global Registry’s scope of non-combustion emissions from fossil fuel production is more comprehensive than many scopes in use in two significant ways.

First, the oil and gas industries are traditionally segmented into upstream, midstream and downstream. Roughly speaking, upstream is what happens at the wellhead and in the field, midstream is transportation to and processing in units such as refineries and petrochemicals factories, and downstream is around distribution and marketing of secondary energy and related products. Emissions factors have mostly been built mirroring this structure, so that it is not uncommon to see upstream emissions factors published by commercial information providers, fossil fuel companies, regulators and others.

The Global Registry aims to establish supply side carbon accounting. From this perspective, when a barrel of oil or ton of coal comes out of the ground, the question emissions factors are designed to address is: what are, or will be, the total emissions in all greenhouse gases by the production of that barrel or ton? In that sense, it supports a “top down” paradigm of looking at the impact of each unit of production’s impact on emissions, rather than what emissions have taken place within the boundaries of a specific jurisdiction, or company. This means also that the methodology does not follow the demand-side accounting system of Greenhouse Gas Scopes 1, 2 and 3, since these apply to emissions specified by a known limited scope, such as an individual company or country.

Supply chain emissions vary considerably from field to field, depending on the physical qualities of oil and gas, operational procedures, sophistication of processing equipment and other factors. But asset-level data is extremely rare in public domain. The Global Registry therefore takes an approach of establishing country-level emissions factors. Some differences in carbon intensity do attach to broad areas, such as a petroleum province, or infrastructure across an entire country, so while there are margins of uncertainty, they are not unmanageable. These uncertainties are typically reflected in presenting not a single point estimate of emissions, but a range with a mid-point, a lower bound, and an upper bound. The Registry adopts this practice.

Another key question of interpretation is how to account for methane, the second largest greenhouse gas and a major component of fossil fuel supply chain emissions. The IPCC has endorsed two different factors to convert methane into carbon dioxide equivalency (“CO2e”), one based on the warming impact it is projected to have over 100 years, and the other based on 20 years. The 20 year factor is considerably higher, because methane decomposes relatively faster in the atmosphere, meaning it becomes less potent over time. The Registry stores all methane factors separately so that total CO2e emissions factors can be produced using either factor.

Details of the methodology are available on the methodology page.