www.sa e- he-clima e.in o A. Wol s eine Ve sion: 27/11/2025
DOI 10.5281/zenodo.16754510 Download his pape : h p://ipcc-co2-budge s.clima e-calcula o .in o
Wha does he IPCC say abou he emaining CO2 budge s?
The goal o he Pa is Ag eemen is o hold “ he inc ease in he global a e age empe a u e o well
below 2°C abo e p e-indus ial le els” and pu sue e o s “ o limi he empe a u e inc ease o 1.5°C
abo e p e-indus ial le els”.
The UN In e go e nmen al Panel on Clima e Change (IPCC) published he ollowing igu es in i s
Six h Assessmen Repo (AR6) Wo king G oup I 20021 (IPCC, 2021, c . Tables SPM.2 and 5.8):
Table 1: Remaining budge s om 2020 onwa ds acco ding o he IPCC (AR6)
Wa ming
Es ima ed emaining
ca bon budge s
Scena io
a ia ion
Geophysical unce ain ies
Non-CO2
scena io
a ia ion
Non-CO2
o cing and esponse
unce ain y
His o ical
empe a u e
unce ain y
ZEC
unce -
ain y
Recen
emissions
unce ain y
P obabili ies:
50%
67%
83%
[°C]
[G CO2 om 2020 on]
[G CO2]
1.5
500
400
300
±220
±220
±550
±420
±20
1.6
650
550
400
1.7
850
700
550
1.8
1000
850
650
1.9
1200
1000
800
2.0
1350
1150
900
A emaining CO2 budge is cu en ly being used up wi h annual emissions o a ound 42 G .
1
He e is a web app o calcula ing linea global emission pa hs ha comply wi h a gi en CO2 budge
( empo a y o e shoo ing can be aken in o accoun ): h p://global-pa hs.clima e-calcula o .in o.
The IPCC w i es abou he CO2 budge (IPCC, 2021, p. 28 ., emphasis and [...] no in he o iginal):
«D.1.1 […] he e is a nea -linea ela ionship be ween cumula i e an h opogenic CO2 emissions and he
global wa ming hey cause. Each 1000 G CO2 o cumula i e CO2 emissions is assessed o likely cause a
0.27°C o 0.63°C inc ease in global su ace empe a u e wi h a bes es ima e o 0.45°C. […] This quan i y
is e e ed o as he ansien clima e esponse o cumula i e CO2 emissions (TCRE). This ela ionship im-
plies ha eaching ne ze o an h opogenic CO2 emissions is a equi emen o s abilize human-induced global
empe a u e inc ease a any le el, bu ha limi ing global empe a u e inc ease o a speci ic le el would
imply limi ing cumula i e CO2 emissions o wi hin a ca bon budge .»
«D.1.2 […] Remaining ca bon budge s ha e been es ima ed o se e al global empe a u e limi s and
a ious le els o p obabili y, based on he es ima ed alue o TCRE and i s unce ain y, es ima es o his o -
ical wa ming [±550 G CO2], a ia ions in p ojec ed wa ming om non-CO2 emissions [±220 G CO2], cli-
ma e sys em eedbacks such as emissions om hawing pe ma os [±220 G CO2], and he global su ace
empe a u e change a e global an h opogenic CO2 emissions each ne ze o [ZEC].»
Rega ding p obabili ies, he IPCC no es (IPCC, 2021, p. 29, emphasis and [...] no in he o iginal):
«This likelihood is based on he unce ain y in ansien clima e esponse o cumula i e CO2 emissions
(TCRE) and addi ional Ea h sys em eedbacks and p o ides he p obabili y ha global wa ming will no
exceed he empe a u e le els […]. Unce ain ies ela ed o his o ical wa ming (±550 G CO2) and non-CO2
o cing and esponse (±220 G CO2) a e pa ially add essed by he assessed unce ain y in TCRE, bu un-
ce ain ies in ecen emissions since 2015 (±20 G CO2) and he clima e esponse a e ne ze o CO2 emis-
sions a e eached (±420 G CO2) a e sepa a e.»
1
Ac ual CO2 emissions in 2024 we e es ima ed a 42.4 G (GCP, 2025). The p ojec ion o 2025 is 42.2 G . See also
oo no e 2.
Remaining global CO2 budge s Page 2 / 3
Upda ed budge s
Since 2023, he Indica o s o Global Clima e Change (IGCC) ini ia i e has published an annual
upda e on emaining CO2 budge s, which also akes in o accoun he la es scien i ic indings. IGCC
publishes he emaining budge s (see Table 2), aking also in o accoun known ac ual emissions
om 2020 onwa ds (c . Fo s e , P.M. e al., 2025). Table 3 shows he esul s con e ed o budge s
om 2020 onwa ds.
2
Table 2: Upda ed budge s om 2025 onwa ds
Wa ming
Es ima ed emaining ca bon budge s
P obabili ies:
50%
67%
83%
[°C]
[G CO2 om 2025 on]
1.5
130
80
30
1.6
310
240
160
1.7
490
390
290
1.8
680
550
430
1.9
860
710
560
2.0
1,050
870
690
Table 3: Recalcula ed upda ed budge s om 2020 onwa ds
Wa ming
Es ima ed emaining ca bon budge s
P obabili ies:
50%
67%
83%
[°C]
[G CO2 om 2020 on]
1.5
336
286
236
1.6
516
446
366
1.7
696
596
496
1.8
886
756
636
1.9
1.066
916
766
2.0
1.256
1.076
896
2
No es on he ollowing able: IGCC de ines LULUCF he e in ele ance o he emaining CO2 budge s acco ding o
he IPCC. P ocess- ela ed emissions om cemen p oduc ion a e included in ‘ ossil’. Cemen ca bona ion sink is aken
in o accoun in GCP.
G CO2
GCP (GCP, 2025)
IGCC (Fo s e , P.M. e al., 2025)
ossil
LUC
o al
ossil
LULUCF
o al
2020
34.4
4.5
38.9
36.0
4.4
40.4
2021
36.0
4.7
40.7
36.5
4.3
40.8
2022
36.7
4.8
41.5
37.1
4.1
41.2
2023
37.3
4.7
42.0
37.8
3.6
41.4
2024
37.8
4.6
42.4
38.2
4.2
42.4
o al
205.5
206.2
Remaining global CO2 budge s Page 3 / 3
Re e ences
Fo s e , P.M. e al., 2025. Indica o s o Global Clima e Change 2024: annual upda e o key
indica o s o he s a e o he clima e sys em and human in luence. [Online]
A ailable a : h ps://essd.cope nicus.o g/a icles/17/2641/2025/
GCP, 2025. [Online]
A ailable a : h ps://globalca bonbudge .o g
[Accessed 13 11 2025].
IPCC, 2021. Summa y o Policymake s. In: Clima e Change 2021: The Physical Science Basis.
Con ibu ion o Wo king G oup I o he Six h Assessmen Repo o he In e go e nmen al Panel
on Clima e Change. [Online]
A ailable a : h ps://www.ipcc.ch/ epo /a 6/wg1/
