For example, very high extinction risk for endemic 
species in biodiversity hotspots is projected to increase at least tenfold 
if warming rises from 1.5°C to 3°C (medium conﬁdence). Projected 
increases in direct ﬂood damages are higher by 1.4 to 2 times at 2°C 
and 2.5 to 3.9 times at 3°C, compared to 1.5°C global warming without 
adaptation (medium conﬁdence). {WGII SPM B.4.1, WGII SPM B.4.2, 
WGII Figure SPM.3, WGII TS Appendix AII, WGII Appendix I Global to 
Regional Atlas Figure AI.46} (Figure 3.2, Figure 3.3)
Global warming of 4°C and above is projected to lead to far-reaching 
impacts on natural and human systems (high conﬁdence). Beyond 
4°C of warming, projected impacts on natural systems include local 
extinction of ~50% of tropical marine species (medium conﬁdence) 
and biome shifts across 35% of global land area (medium conﬁdence). 
At this level of warming, approximately 10% of the global land area 
is projected to face both increasing high and decreasing low extreme 
streamﬂow, affecting, without additional adaptation, over 2.1 billion people 
(medium conﬁdence) and about 4 billion people are projected to 
experience water scarcity (medium conﬁdence). At 4°C of warming, the 
global burned area is projected to increase by 50 to 70% and the 
fire frequency by ~30% compared to today (medium confidence). 
{WGII SPM B.4.1, WGII SPM B.4.2, WGII TS.C.1.2, WGII TS.C.2.3, 
WGII TS.C.4.1, WGII TS.C.4.4} (Figure 3.2, Figure 3.3)