78
Section 3
Section 1
Section 3
impacts on populations in low elevation coastal zones. If global 
warming increases, some compound extreme events124 will 
become more frequent, with higher likelihood of unprecedented 
intensities, durations or spatial extent (high confidence). The 
Atlantic Meridional Overturning Circulation is very likely to weaken 
over the 21st century for all considered scenarios (high conﬁdence), 
however an abrupt collapse is not expected before 2100 (medium 
conﬁdence). If such a low probability event were to occur, it would very 
likely cause abrupt shifts in regional weather patterns and water cycle, 
124 See Annex I: Glossary. Examples of compound extreme events are concurrent heatwaves and droughts or compound ﬂooding. {WGI SPM Footnote 18}
such as a southward shift in the tropical rain belt, and large impacts 
on ecosystems and human activities. A sequence of large explosive 
volcanic eruptions within decades, as have occurred in the past, is a 
low-likelihood high-impact event that would lead to substantial cooling 
globally and regional climate perturbations over several decades. 
{WGI SPM B.5.3, WGI SPM C.3, WGI SPM C.3.1, WGI SPM C.3.2, 
WGI SPM C.3.3, WGI SPM C.3.4, WGI SPM C.3.5, WGI Figure SPM.8, 
WGI Box TS.3, WGI Figure TS.6, WGI Box 9.4; WGII SPM B.4.5, WGII SPM C.2.8; 
SROCC SPM B.2.7} (Figure 3.4, Cross-Section Box.2)
3.2 Long-term Adaptation Options and Limits
With increasing warming, adaptation options will become more constrained and less effective. At higher levels 
of warming, losses and damages will increase, and additional human and natural systems will reach adaptation 
limits. Integrated, cross-cutting multi-sectoral solutions increase the effectiveness of adaptation.