Editing IPCC:AR6/WGII/Chapter-15 (section)

=== 15.2.1 Points of Departure on Exposure, Vulnerability, Impacts and Risks ===

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Scientific studies since AR5 confirm that global temperature will continue to increase even if greenhouse gas emissions are drastically reduced and will escalate the vulnerability, impacts and multiple interrelated risks experienced by small islands ( ''high confidence'' ) ( [[#IPCC--2018|IPCC, 2018]] ). A greater sense of urgency in lowering global greenhouse gas emissions and a call for action now is resonating among small island states.

Post-AR5 new studies confirm observed impacts on the natural and human systems and indicate projected risks in both these systems over time. Over the past four decades, there was a significant increase in the probability of the global exceedances of tropical cyclones (TCs) of major intensity ( [[#Kossin--2020|Kossin et al., 2020]] ), a trend confirmed by the occurrence of a growing number of intense TCs affecting the Atlantic and Pacific regions since AR5 ( [[#Magee--2016|Magee et al., 2016]] ; [[#Bhatia--2019|Bhatia et al., 2019]] ; [[#Knutson--2019|Knutson et al., 2019]] ). Also, scientific evidence since AR5 has confirmed that tropical corals are presently at high risk ( ''very high confidence'' ) and if global warming exceeds 1.5°C, known coral reef restoration options may be ineffective ( [[#IPCC--2018|IPCC, 2018]] ). Even achieving emission reduction targets consistent with the ambitious goal of 1.5°C of global warming under the Paris Agreement will result in the further loss of 70–90% of reef-building corals compared to today, with 99% of corals being lost under warming of 2°C or more above the pre-industrial period ( ''high confidence'' ) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ).

Additionally, since the last assessment, more robust scientific evidence exists on the impacts of sea level rise (SLR) and extreme sea level (ESL) events on small islands. Under Representative Concentration Pathways emission scenarios, RCP2.6, RCP4.5 and RCP8.5, many low-lying coastal areas at all latitudes, including small islands, will experience SLR and ESL events such as coastal storm surges and coastal flooding more frequently in the coming decades ( [[IPCC:Wg2:Chapter:Chapter-4#4.2.3|Section 4.2.3.4.1]] ; [[#IPCC--2019|IPCC, 2019]] ). SLR and ESL events will affect atoll islands and islands with higher elevations differently. New studies forecast that small islands are ''likely'' to experience some of the largest increases in endemic extinctions and may substantially contribute to future global biodiversity loss as well as to impaired ecosystem functioning ( [[#Fortini--2015|Fortini et al., 2015]] ; [[#Vogiatzakis--2016|Vogiatzakis et al., 2016]] ; [[#Cramer--2018|Cramer et al., 2018]] ). Scientific evidence points to large population reductions with an extinction risk of 100% for endemic species within insular biodiversity hotspots by 2100 ( [[#IPBES--2018|IPBES, 2018]] ; [[#Manes--2021|Manes et al., 2021]] ). An overarching concern since AR5 is the reduced habitability of small islands. Eight key risks (KRs) affecting the habitability of small islands are identified in this assessment and these are covered in the pertinent sections of this chapter which assess adaptation responses.

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