It was after a long day down­play­ing cli­mate sci­ence, play­ing coy about human rights abus­es and ​“for­get­ting” basic details of his 41-year career at Exxon­Mo­bil that the company’s for­mer CEO and prospec­tive Sec­re­tary of State — Rex Tiller­son — got a ques­tion from Sen. Jeanne Sha­heen (D‑NH) about fos­sil fuel subsidies.

If those subsidies were redacted, some 20 billion barrels of oil could stay in the ground.

Refer­ring to the G20 nations’ 2009 com­mit­ment to phase out fos­sil fuel sub­si­dies, she asked, ​“If con­firmed, how would you as Sec­re­tary of State fol­low through on our inter­na­tion­al com­mit­ment to phase out those … subsidies?”

“I am not aware of any­thing the fos­sil fuel indus­try gets that I would char­ac­ter­ize as a sub­sidy,” Tiller­son answered flat­ly. ​“Rather it’s sim­ply the appli­ca­tion of the tax code broad­ly that applies to all industry.”

“How peo­ple should see that is Rex Tiller­son lying under oath,” says Janet Red­man, U.S. Pol­i­cy Direc­tor at Oil Change Inter­na­tion­al. The IMF, World Bank and World Trade Orga­ni­za­tion all refer to the kinds of spe­cial treat­ment Exxon and oth­er fos­sil fuel com­pa­nies receive through the tax code as subsidies.

In fact, Red­man says, fos­sil fuel com­pa­nies col­lect some $17 bil­lion in state and fed­er­al sub­si­dies each year. Exxon alone could reap as much as $1 bil­lion in tax relief. Though fed­er­al report­ing require­ments don’t man­date com­pa­nies to report which sub­si­dies they enjoy, tax breaks like Intan­gi­ble Drilling Costs apply specif­i­cal­ly to (pre­dictably) drilling oper­a­tions that can only be per­formed by cor­po­ra­tions in the oil, coal and nat­ur­al gas business.

A new report (sum­ma­rized here) from the Stock­holm Envi­ron­ment Insti­tute and Earth­Track finds that 45 per­cent of dis­cov­ered but not-yet-devel­oped oil reserves in the U.S. would depend on ener­gy sub­si­dies to be prof­itable at cur­rent oil prices. This means that if those sub­si­dies were redact­ed, per the G20 nations’ com­mit­ment, some 20 bil­lion bar­rels of oil could stay in the ground. ​“The effect of that is not build­ing 100 coal fired pow­er plan and let­ting them run for 23 years,” Red­man says. If burned, the study esti­mates, the sub­si­dized reserves would account for a full 1 per­cent of the car­bon the world can burn — and up to a quar­ter of the oil the U.S. can burn — to keep a decent chance of stay­ing below 2 degree Cel­sius tem­per­a­ture rise.

Part of the rea­son that so much fur­ther oil devel­op­ment is depen­dent on sub­si­dies is that oil prices have faced a slug­gish recov­ery since crash­ing in 2016. But even if those prices rebound, Red­man says, ​“the sub­si­dies will still flow. That mon­ey will just go direct­ly to cor­po­rate pock­ets, which gives them more cash on hand to do more explo­ration or to pay lob­by­ists or make con­tri­bu­tions to con­gres­sion­al campaigns.”

In oth­er words, funds freed up by sub­si­dies can be put toward things like Exxon’s con­sid­er­able lob­by­ing bud­get and pool of funds for cli­mate deny­ing think tanks, which it has fund­ed to the tune of more than $33 mil­lion since 1998.

Red­man adds, ​“These com­pa­nies — some of the wealth­i­est and most pow­er­ful in the world — are not pay­ing their fair share of taxes.”

Tiller­son pled sim­i­lar igno­rance ear­li­er in the day, stat­ing that ​“to my knowl­edge, Exxon nev­er direct­ly lob­bied against sanc­tions.” As sev­er­al out­lets point­ed out, this isn’t true: While Tiller­son was CEO, Exxon lob­bied Con­gress on three dif­fer­ent sanc­tions bills. (Exxon respond­ed direct­ly to the exchange via Twitter.)

But he isn’t alone in claim­ing sub­si­dies aren’t real­ly sub­si­dies. In a 2016 report, the Amer­i­can Petro­le­um Insti­tute — the lob­by­ing arm of the fos­sil fuel indus­try, of which Exxon is a mem­ber — called the idea of fos­sil fuel sub­si­dies ​“a well-cir­cu­lat­ed myth,” claim­ing “ there are no tar­get­ed tax cred­its cur­rent­ly being used by industry.”

Of course, Tiller­son is in the run­ning to be Sec­re­tary of State, not a fos­sil fuel lob­by­ist. If he is con­firmed, those lines could become more blurred than ever.