1.5°C or 2°C: a conduit’s view from the science-policy interface at COP20 in Lima, Peru

Table 1 Likelihoods of staying below specific temperature targets for various emission concentration pathways

CO ₂ -eq Concentration in 2100 (CO ₂ -eq) * Category label (conc. range)	Subcategories	Relative position of the RCPs *	Change in CO ₂ -eq emissions compared to 2010 (in %) *		Likelihood of staying below a specific temperature level over the 21st century (relative to 1850–1900) *
	Subcategories	Relative position of the RCPs *	2050	2100	1.5°C	2°C	3°C	4°C
<430	Only a limited number of individual model studies have explored levels below 430 ppm CO₂-eq*
450 (430 to 480)	Total range*	RCP2.6	−72 to −41	−118 to −78	More unlikely than likely	Likely	Likely	Likely
500 (480 to 530)	No overshoot of 530 ppm CO₂-eq		−57 to −42	−107 to −73	Unlikely *	More likely than not
500 (480 to 530)	Overshoot of 530 ppm CO₂-eq		−55 to −25	−114 to −90		About as likely as not
550 (530 to 580)	No overshoot of 580 ppm CO₂-eq		−47 to −19	−81 to −59		More unlikely than likely ^*
550 (530 to 580)	Overshoot of 580 ppm CO₂-eq		−16 to 7	−183 to −86
580 to 650	Total range	RCP4.5	−38 to 24	−134 to −50
(650 to 720)	Total range	RCP4.5	−11 to 17	−54 to −21		Unlikely *	More likely than not
(720 to 1,000)*	Total range	RCP6.0	18 to 54	−7 to 72	Unlikely *	Unlikely *	More unlikely than likely
>1,000*	Total range	RCP8.5	52 to 95	74 to 178	Unlikely *	Unlikely *	Unlikely	More unlikely than likely

Source: IPCC AR5 Synthesis Report, 2014 [3]. *Footnotes explained in the original.

ISSN: 2053-7565