Further information: Effects of global warming#Social systems and Regional effects of global warming#Regional impacts
Vulnerability of human societies to climate change mainly lies in the effects of extreme weather events rather than gradual climate change.[158] Impacts of climate change so far include adverse effects on small islands,[159] adverse effects on indigenous populations in high-latitude areas,[160] and small but discernable effects on human health.[161] Over the 21st century, climate change is likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts.[162] Most economic studies suggest that global warming would reduce world gross domestic product (GDP).[163][164]