Editing IPCC:AR6/WGI/Chapter-12 (section)

==== 12.4.7.1 Heat and Cold ====

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'''Mean air temperature:''' Significant warming trends are clearly evident in the small islands, such as those in the Pacific, CAR, and western Indian Ocean, particularly over the latter half of the 20th century (see Figure Atlas.11; Atlas.10.2; Cross-Chapter Box Atlas.2, Table 1). This observed warming signal in the tropical western Pacific has been attributed to anthropogenic forcing ( [[#Wang--2016|Wang et al., 2016]] ). There is ''high confidence'' of warming over small islands even at 1.5°C GWL (Atlas.10.4 and Figure Atlas.28; [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ). Mean temperature is ''very likely'' to increase by 1°C–2°C (2°C–4°C) by 2041–2060 (2081–2100) under RCP8.5 (BOM and CSIRO, 2014) and SSP3-7.0 (Atlas.10.4, Figure 4.19 and Figure Atlas.12; [[#Almazroui--2021|Almazroui et al., 2021]] ).

'''Extreme heat:''' Observational records indicate warming trends in the temperature extremes since the 1950s in CAR and the Pacific small islands ( ''high confidence'' ) (Sections 11.3.2 and 11.9, and Table 11.13). A detectable anthropogenic increase in summer heat stress has been identified over a number of island regions in CAR, western tropical Pacific, and tropical Indian Ocean, based on wet bulb globe temperature (WBGT) index trends for 1973–2012 ( ''medium confidence'' ) ( [[#Knutson--2016|Knutson and Ploshay, 2016]] ). An increasing trend in the maximum daytime heat index is also noted in CAR during the 1980–2014 period, as well as more extreme heat events since 1991 ( [[#Ramirez-Beltran--2017|Ramirez-Beltran et al., 2017]] ).

Compared with the recent past, it is ''likely'' that the intensity and frequency of hot (cold) temperature extremes will increase (decrease) in the small islands ( [[IPCC:Wg1:Chapter:Chapter-11#11.9|Section 11.9]] and Table 11.13; BOM and CSIRO, 2014). Warm spell conditions will occur up to half the year in CAR at 1.5°C GWL with an additional 70 days at 2°C ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ; [[#Taylor--2018|Taylor et al., 2018]] ), with livestock temperature–humidity tolerance thresholds increasingly surpassed ( [[#Lallo--2018|Lallo et al., 2018]] ). In CAR, a median increase of more than a month per year where temperatures exceed 35°C is projected by end of the 21st century under SSP5-8.5 (Figure 12.4a–c and Figure 12.SM.1). Heatwaves are projected to increase in CAR by the mid- and end-century under RCP8.5 (Sections 11.3.5 and 11.9, and Table 11.13). Figure 12.4d–f and Figure 12.SM.2 also show an increase of about 30–60 days in which HI exceeds 41°C by 2041–2060 under SSP5-8.5 relative to 1995–2014 in CAR, with an additional increase of about 50–100 days by end of the 21st century for RCP8.5/SSP5-8.5, but this increase remains below 50 days for RCP2.6/SSP1-2.6. The Pacific Islands region is also among those projected to have an increase in WBGT by end-century under RCP8.5, increasing the risk of heat stress in the region ( [[#Newth--2018|Newth and Gunasekera, 2018]] ).

'''It is''' very likely '''that the significant recent warming trends observed in the small islands will continue in the 21st century, which will''' likely '''further increase heat stress in these regions.'''

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