{WGII Figure SPM.3}
121 The Reasons for Concern (RFC) framework communicates scientiﬁc understanding about accrual of risk for ﬁve broad categories (WGII Figure SPM.3). RFC1: Unique and 
threatened systems: ecological and human systems that have restricted geographic ranges constrained by climate-related conditions and have high endemism or other distinctive 
properties. Examples include coral reefs, the Arctic and its Indigenous Peoples, mountain glaciers and biodiversity hotspots. RFC2: Extreme weather events: risks/impacts to 
human health, livelihoods, assets and ecosystems from extreme weather events such as heatwaves, heavy rain, drought and associated wildﬁres, and coastal ﬂooding. RFC3: 
Distribution of impacts: risks/impacts that disproportionately affect particular groups due to uneven distribution of physical climate change hazards, exposure or vulnerability. 
RFC4: Global aggregate impacts: impacts to socio-ecological systems that can be aggregated globally into a single metric, such as monetary damages, lives affected, species lost 
or ecosystem degradation at a global scale. RFC5: Large-scale singular events: relatively large, abrupt and sometimes irreversible changes in systems caused by global warming, 
such as ice sheet instability or thermohaline circulation slowing. Assessment methods include a structured expert elicitation based on the literature described in WGII SM16.6 
and are identical to AR5 but are enhanced by a structured approach to improve robustness and facilitate comparison between AR5 and AR6. For further explanations of global 
risk levels and Reasons for Concern, see WGII TS.AII. {WGII Figure SPM.3}
changes in food availability and diet quality are estimated to increase 
nutrition-related diseases and the number of undernourished people, 
affecting tens (under low vulnerability and low warming) to hundreds of 
millions of people (under high vulnerability and high warming), particularly 
among low-income households in low- and middle-income countries in 
sub-Saharan Africa, South Asia and Central America (high conﬁdence). 
For example, snowmelt water availability for irrigation is projected 
to decline in some snowmelt dependent river basins by up to 20% 
(medium conﬁdence).