System 
transitions151 consistent with pathways that limit warming to 1.5°C 
(>50%) with no or limited overshoot are more rapid and pronounced 
in the near-term than in those that limit warming to 2°C (>67%) 
(high conﬁdence). Such a systemic change is unprecedented in terms 
of scale, but not necessarily in terms of speed (medium conﬁdence). 
The system transitions make possible the transformative adaptation 
required for high levels of human health and well-being, economic and 
social resilience, ecosystem health, and planetary health. {WGII SPM 
A, WGII Figure SPM.1; WGIII SPM C.3; SR1.5 SPM C.2, SR1.5 SPM 
C.2.1, SR1.5 SPM C.2, SR1.5 SPM C.5}
Feasible, effective and low-cost options for mitigation and 
adaptation are already available (high conﬁdence) (Figure 4.4). 
Mitigation options costing USD 100 tCO2-eq–1 or less could reduce 
151 System transitions involve a wide portfolio of mitigation and adaptation options that enable deep emissions reductions and transformative adaptation in all sectors. This report 
has a particular focus on the following system transitions: energy; industry; cities, settlements and infrastructure; land, ocean, food and water; health and nutrition; and society, 
livelihood and economies. {WGII SPM A, WGII Figure SPM.1, WGII Figure SPM.4; SR1.5 SPM C.2}
152 See Annex I: Glossary.
global GHG emissions by at least half the 2019 level by 2030 (options 
costing less than USD 20 tCO2-eq–1 are estimated to make up more 
than half of this potential) (high conﬁdence) (Figure 4.4). The 
availability, feasibility152 and potential of mitigation or effectiveness 
of adaptation options in the near term differ across systems and 
regions (very high confidence).