As much as half of the oil and gas produced by the largest international majors may not be covered by their own emissions-reduction targets due to the impact of joint ventures on carbon accounting, according to a new report published by the Environmental Defense Fund (EDF).

The study looks specifically at non-operated joint ventures (NOJVs) in which the seven largest international oil companies (IOCs) are partnered with national oil companies, typically providing technical expertise and capital in exchange for a share of production.