RESEARCH HIGHLIGHT
Na ional Science Re iew
12: nwa 249, 2025
h ps://doi.o g/10.1093/ns /nwa 249
Ad ance access publica ion 20 June 2025
EARTH SCIENCES
Legacy leaks, las ing liabili ies: ele a ing abandoned oil and
gas wells in clima e change mi iga ion policy
Lena Höglund-Isaksson
As he wo ld in ensi ies i s e o s o
educe g eenhouse gas emissions, a -
ge ing me hane emissions has eme ged
wi h heigh ened u gency. Me hane’s
a mosphe ic li e ime is sho , bu i s
global wa ming po en ial o e 20 yea s
is > 80 imes ha o ca bon dioxide [1 ].
Reducing me hane emissions is he e-
o e among he mos e ec i e s a egies
o slowing nea - e m global wa ming.
Among me hane sou ces, one has e-
mained especially elusi e: abandoned
oil and gas (AOG) wells. These wells,
d i l led o e decades o ossil uel ex ac-
ion, o en con inue leaking me hane
long a e p oduc ion ends. Many a e
imp ope ly sealed, unmoni o ed, and
undocumen ed in o icial in en o ies.
Some a e ‘o phaned’, meaning no legally
esponsible ope a o exis s. Thei emis-
sions a e di use bu pe sis en , ep e-
sen ing a me hane sou ce in need o close
moni o ing and con ol long a e he
wo ld has mo ed away om oil and gas
dependency.
AOG wells a e no only a me hane
p oblem. Unplugged o deg aded wells
pose se ious heal h h ea s o local
communi ies as hey con amina e
aqui e s, elease oxic ola ile o ganic
compounds and—unde ce ain p es-
su e condi ions—e en pose explosion
haza ds [2 ]. They also h ea en he
long- e m iabili y o ca bon cap u e and
s o age (CCS) in a ec ed o ma ions,
whe e leakage h ough legacy wellbo es
can unde mine con ainmen in eg i y
[3 ].
IPCC’s Six h Assessmen Repo
Wo king G oup III [4 ] acknowledges
me hane om AOG wells as a sou ce o
unce ain y, bu o e s no global emission
es ima e. S a ing in 2024, he newly
e ised epo ing amewo k o he UN-
FCCC asks Annex-1 coun ies o epo
AOG emissions as a sepa a e ca ego y
[5 ]. Aus alia, Canada, he UK and he
USA adhe ed o his call and epo ed
o yea 2020 a o al 0.32 M me hane
om he sou ce, whe eo 0.30 M was
om he USA alone. The e is acco dingly
a s iking lack o comple eness in he
epo ing o hese emissions a he global
and na ional scales, including o ela-
i ely p ospe ous coun ies like No way
and Romania.
The s udy by Lei e al. [6 ] ep esen s
a majo s ep o wa d in ou unde s and-
ing o he scale o he abandoned wells
p oblem, and opens up o including i
as a measu able componen o he global
me hane budge . The au ho s de elop an
unpa al lel led ha monized global in en-
o y o me hane emissions om AOG
wells, co e ing 4.5 mi l lion wel ls in 127
coun ies, and p o iding a i s global
benchma k: 0.4 M o me hane eleased
om abandoned wells in 2022. Al hough
modes in size, hey ep esen < 1%
o global oil and gas sys ems me hane
emissions, hei pe sis ency and lack o
legal owne ship make hem impo an o
moni o and quan i y. Lei e al. ’s da ase ,
CEADs-AOGI, includes well-le el in o -
ma ion o > 420 0 0 0 si es, and also co -
e s well a ibu es ele an o he de el-
opmen o e ec i e mi iga ion s a egies,
such as esou ce ype, e ain, plugging
and owne ship s a us. By inco po a ing
hese in o a p ocess-based bo om-up
emissions model, he au ho s a e able o
econs uc his o ical si e-le el emissions
and p oduce scena io-based p ojec ions
o u u e ajec o ies. Lei e al. also in-
oduce a no el co po a e a ibu ion
analysis, linking me hane emissions o
his o ical ope a o s. In se e al coun ies,
a small numbe o mul ina ional i ms
a e associa ed wi h a disp opo iona e
sha e o legacy emissions. This aises he
possibili y o e ospec i e accoun abili y
amewo ks, whe e pas emi e s could be
held inancially esponsible o cleanup.
Such an app oach could suppo jus
ansi ion s a egies, pa icula ly in
esou ce-limi ed se ings whe e na ional
go e nmen s inhe i he bu den o
emedia ion.
A s iking inding is he p esence o
‘supe -emi e s’ and he high deg ee o
in e mi ency and spa ial a iabili y in
me hane emission a es ac oss AOG
wells. Au ho s highligh ha his is no
only a p oblem o onsho e wells; shal-
low o sho e wells like in he No h Sea
can exhibi huge emission a es due o
challenging decommissioning condi ions
and aging legacy in as uc u e. This calls
o equen moni o ing o emissions
om abandoned wells, e.g. using sa elli e
emo e sensing echnology. Like o so
many o he me hane sou ce sec o s,
e ec i e mi iga ion s a egies mus com-
bine equen moni o ing o emissions
wi h si e-speci ic bo om-up in o ma ion
on he geological con ex , echnological
se -up, and owne ship s uc u es, i.e.
he kind o in o ma ion compiled and
p esen ed he e by Lei e al. in g ea de ail
o AOG wells. I ’s when si e-speci ic
© The Au ho (s) 2025. Published by Ox o d Uni e si y P ess on behal o China Science Publishing & Media L d. This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e
Commons A ibu ion License (h ps://c ea i ecommons.o g/licenses/by/4.0/), which pe mi s un es ic ed euse, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal
wo k is p ope ly ci ed.
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Na l Sci Re , 2025, Vol. 12, nwa 249
bo om-up in o ma ion is linked o
op-down emissions quan i ica ions ha
egula o s ha e he ools o jump-s a
s ong and legally binding me hane
mi iga ion e o s.
FUNDING
LHI g a e ully acknowledges unding om he Eu-
opean Commission EU-CHINA-BRIDGE p ojec
no. 101137971 unde HORIZON-CL5-2023-D1-
02-01.
Con lic o in e es s a emen . None decla ed.
Lena Höglund-Isaksson
Pollu ion Managemen G oup, Ene gy, Clima e and
En i onmen P og am, In e na ional Ins i u e o
Applied Sys ems Analysis (IIASA), Aus ia
E-mail:
[email p o ec ed]
REFERENCES
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Assessmen Repo o he In e go e nmen al Panel
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si y P ess, 2021.
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2023; 18 : 074012.
3. Celia MA, Bachu S, No dbo en JM e al. Wa e
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4. Cla ke L, Wei YM, De La Vega Na a o A e al.
Ene gy sys ems. In: Shukla PR, Skea J, Slade R
e al. (eds.). Clima e Change 2022: Mi iga ion o
Clima e Change. Con ibu ion o Wo king G oup III
o he Six h Assessmen Repo o he In e go -
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Camb idge Uni e si y P ess, 2022.
5. Uni ed Na ions Clima e Change. Na ional In en o y
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annex-i-pa ies/2024 (19 June 2025, da e las
accessed).
6. Lei T, Chen X, Ma S e al. Na l Sci Re 2025; 12 :
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©The Au ho (s) 2025. Published by Ox o d Uni e si y P ess on behal o China Science Publishing & Media L d. This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e
Commons A ibu ion License ( h ps://c ea i ecommons.o g/licenses/by/4.0/), which pe mi s un es ic ed euse, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal
wo k is p ope ly ci ed.
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