Exxon Mobil Corp. and Royal Dutch Shell emitted more carbon dioxide last year than they did two years prior, despite producing less oil and natural gas.
The companies produced about 10 percent more greenhouse gases for each barrel of oil or gas they pumped compared to 2011, The Wall Street Journal reported Wednesday.
New production also requires energy-intensive practices like cooling natural gas for transportation or heating oil so it can flow, the Journal said.
The data are based on reports the companies provided to the Carbon Disclosure Project, due to be released publicly Wednesday.
Exxon said it increased the efficiency of its refining by 10 percent and manufacturing by 12 percent between 2002 and 2012, though it does not have a goal for reducing emissions because it does not believe those measures to be effective in fighting climate change.
Shell said its increased emissions come from pumping oil and gas that requires more energy to access, and predicted its emissions would continue to rise, the Journal reported. But Shell also said it is committed to reducing emissions.
Chevron Corp.’s greenhouse gas emissions fell 4 percent in the reporting period.