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

==== Atlas.7.1.4 Assessment and Synthesis of Projections ====

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Figure Atlas.22 and the Interactive Atlas synthesize regional mean changes in annual mean surface air temperature and precipitation for the Central American reference regions for CMIP6, CMIP5 and CORDEX for different warming levels and time periods. At the 1.5°C GWL, it is ''very likely'' that average annual temperature in Central America over land surpasses 1.3°C (CAR), 1.7°C (NCA) and 1.6°C (SCA). For the 3°C GWL, the corresponding projected ensemble mean regional warming values are 2.7°C (CAR), 3.5°C (NCA) and 3.1°C (SCA). CAR average annual warming is below the level of global warming, while the two continental reference regions are close to the global warming level with CMIP6 and CMIP5 showing very consistent results (Figure Atlas.22). However, when focusing on time slices instead of warming levels, the CMIP6 projections show systematically higher median values than CMIP5. CORDEX results are also consistent with the previous findings, though the subset of driving models spans a smaller range of uncertainty, particularly over CAR. Results have also been reported for this region based on CMIP5, CMIP6 and downscaled simulations over the CORDEX CAM domain or similar smaller domains ( [[#Taylor--2013b|Taylor et al., 2013b]] ; [[#Nakaegawa--2014|Nakaegawa et al., 2014]] ; [[#Imbach--2018|Imbach et al., 2018]] ; [[#Vichot-Llano--2019|Vichot-Llano et al., 2019]] ; [[#Almazroui--2021|Almazroui et al., 2021]] ). Statistical downscaling methods have been also applied to CMIP5 projections to obtain bias-adjusted regional projections ( [[#Colorado-Ruiz--2018|Colorado-Ruiz et al., 2018]] ; [[#Taylor--2018|Taylor et al., 2018]] ; [[#Vichot-Llano--2019|Vichot-Llano et al., 2019]] ).

Global and regional models consistently project warming in the whole region for the end of the century, under RCP4.5 and RCP8.5 for CMIP5 projections with greater warming for continental compared to insular territories, ''likely'' reaching values between 2°C and 4°C ( ''high confidence'' ) ( [[#Campbell--2011|Campbell et al., 2011]] ; [[#Karmalkar--2011|Karmalkar et al., 2011]] ; [[#Cavazos--2012|Cavazos and Arriaga-Ramírez, 2012]] ; [[#Cantet--2014|Cantet et al., 2014]] ; [[#Chou--2014|Chou et al., 2014]] ; [[#Coppola--2014|Coppola et al., 2014]] ; [[#Hidalgo--2017|Hidalgo et al., 2017]] ; [[#Colorado-Ruiz--2018|Colorado-Ruiz et al., 2018]] ; [[#Imbach--2018|Imbach et al., 2018]] ). The greatest warming of 5.8°C for the end of the century was projected for northern Mexico under RCP8.5 ( [[#Colorado-Ruiz--2018|Colorado-Ruiz et al., 2018]] ), using an ensemble of CMIP5 GCMs (Interactive Atlas).

Regarding precipitation, it is ''likely'' that the annual average precipitation changes for the 1.5°C GWL will be in the ranges of –11 to 0% in CAR, from –12 to 0% in SCA, and from –10 to +3% in NCA (Interactive Atlas). For the 3°C GWL, the corresponding annual average precipitation changes will be from –17 to –2% in CAR, from –16 to +2% in NCA, and from –23 to 0% in SCA. A clear drying tendency is observed for the 3°C GWL relative to the 1.5°C GWL. [[#Maloney--2014|Maloney et al. (2014)]] examined 21st-century climate projections of North American climate in CMIP5 models under RCP8.5, including Central America and the Caribbean. Summer drying was projected in CAR and SCA for most of the models, with good agreement. The strongest drying is projected to occur during July and August which are the months when the MSD occurs in many sub-regions (Figure Atlas.22 and the Interactive Atlas). Intensification of the MSD in SCA was also projected by using the Rossby Centre Regional Climate Model (RCA4; [[#Corrales-Suastegui--2020|Corrales-Suastegui et al., 2020]] ), but with a future decrease in area and frequency (Cross-Chapter Box [[#Atlas.2|Atlas.2]] ). They also found a projected intensification of CLLJ and drying for the future time slice of 2071–2095, relative to their baseline of 1981–2005. Decreased precipitation was also projected for SCA ( [[#Imbach--2018|Imbach et al., 2018]] ) with the 8-km resolution Eta RCM during the rainy season, including an intensification of the MSD, although no significant change was projected for the CLLJ.

[[#Colorado-Ruiz--2018|Colorado-Ruiz et al. (2018)]] assessed an ensemble of 14 GCMs from CMIP5 for a 1971–2000 baseline period, projecting precipitation decreases of between 5% and 10% by the end of the century for the RCP4.5 and RCP8.5 scenarios respectively. The greatest decrease in precipitation is projected during summer reaching 13%, especially in southern Mexico, Central America and the Caribbean. Dynamically downscaled simulations ( [[#Bukovsky--2015|Bukovsky et al., 2015]] ) also projected a decrease of precipitation for the middle of the century (2041–2069) relative to 1971–1999 for the north of Mexico, though despite good agreement amongst the models, these results must be considered of ''low confidence'' , because of their poor simulation of important monsoon physical processes. [[#Vichot-Llano--2021a|Vichot-Llano et al. (2021a)]] used a multi-parameter ensemble of RegCM4, driven by the CMIP5 global model HagGEM2-ES projections to conclude that, relative to the 1975–2004 baseline, in the near (2020–2049) and more prominently in the far (2070–2099) future, drier conditions will prevail at over the eastern Caribbean. The projected future warming trend was statistically significant at the 95% confidence level over CAR and SCA. [[#Almazroui--2021|Almazroui et al. (2021)]] used an ensemble of 31 CMIP6 models to estimate climate change signals of temperature and precipitation in six reference regions in North and Central America and the Caribbean, finding a decrease in precipitation (10–30%) over Central America and the Caribbean under three scenarios with regional and seasonal variations.

There is ''high agreement'' and ''high confidence'' in the projected decrease of precipitation by the end of the century for most of the region, particularly for annual and summer precipitation, but there is ''low confidence'' on the magnitude of this decrease which varies between 5% and 50% for different projections and different sub-regions (see extended information in the Interactive Atlas).

The status of climateextreme trends and projections for the region has been assessed in [[IPCC:Wg1:Chapter:Chapter-11|Chapter 11]] and the main findings are synthesized here. There is ''high confidence'' in the projections of significant heatwave events at the end of the century in SCA ( [[#Angeles-Malaspina--2018|Angeles-Malaspina et al., 2018]] ) and an increase in warm days and warm nights over this region and CAR (Stennett- [[#Brown--2017|Brown et al., 2017]] ). For CAR islands, using dynamically downscaled CMIP3 models, [[#Karmalkar--2013|Karmalkar et al. (2013)]] projected an increase in drought severity at the end of the century, mainly due to a precipitation decrease during the early wet season. In SCA, projections suggest an increase in the MSD ( [[#Imbach--2018|Imbach et al., 2018]] ) and an increase in consecutive dry days ( [[#Chou--2014|Chou et al., 2014]] ), consistent with the projections of Stennett- [[#Brown--2017|Brown et al. (2017)]] .

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