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

==== Atlas.7.1.1 Key Features of the Regional Climate and Findings From Previous IPCC Assessments ====

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===== Atlas.7.1.1.1 Key Features of the Regional Climate =====

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The Central America and Caribbean region is assessed considering three reference regions Southern Central America (SCA), including the isthmus and the Yucatan Peninsula; Northern Central America (NCA), including Mexico (centre and north); and the Caribbean (CAR), including the Greater Antilles, the Lesser Antilles, the Bahamas and other small islands (see Figure Atlas.22); NCA is also covered in Section [[#Atlas.9|Atlas.9]] North America.

Precipitation in most of SCA is characterized by two maxima in June and September, an extended dry season from November to May, and a shorter relatively dry season between July and August known as the midsummer drought (MSD; Chapter 10; [[#Magaña--1999|Magaña et al., 1999]] ; [[#Perdigón-Morales--2018|Perdigón-Morales et al., 2018]] ). To some extent, precipitation seasonality is explained by the migration of the Inter-tropical Convergence Zone (ITCZ) ( [[#Taylor--2005|Taylor and Alfaro, 2005]] ). The climate of NCA is temperate to the north of the Tropic of Cancer, with a marked difference between winter and summer, modulated by the North American Monsoon (NAmerM, [[IPCC:Wg1:Chapter:Chapter-8#8.3.2.4.4|Section 8.3.2.4.4]] ). The CAR region has two main seasons, characterized by differences in temperature and precipitation. The wet or rainy season, with higher values of temperature and accumulated precipitation, occurs during the boreal summer and part of spring and autumn ( [[#Gouirand--2020|Gouirand et al., 2020]] ). The MSD is also present in the Greater Antilles and the Bahamas ( [[#Taylor--2005|Taylor and Alfaro, 2005]] ), influenced by the oscillations of the North Atlantic Subtropical High (NASH), interacting with the Pacific and Atlantic branches of the ITCZ and modulated by the Atlantic Warm Pool and the Caribbean low-level jet (CLLJ), while the Atlantic ITCZ is responsible for the unimodal rainfall cycle of the central and southern Lesser Antilles ( [[#Martinez--2019|Martinez et al., 2019]] ). The CLLJ is a persistent climatological feature of the low-level circulation in the Central Caribbean, with a characteristic semi-annual cycle with maxima in the summer (main) and winter (secondary) ( [[#Amador--1998|Amador, 1998]] ; [[#Magaña--1999|Magaña et al., 1999]] ; [[#Whyte--2008|Whyte et al., 2008]] ). Temporal variability is influenced by several large-scale atmospheric modes ( [[IPCC:Wg1:Chapter:Annex-iv|Annex IV]] and Table Atlas.1). A significant positive correlation between precipitation rates in CAR and the Atlantic Multi-decadal Variability (AMV) was found ( [[#Enfield--2001|Enfield et al., 2001]] ). A similar result was found in southern Mexico (north of SCA) in the MSD region (see case-study discussion in [[IPCC:Wg1:Chapter:Chapter-10#10.4.2.3|Section 10.4.2.3]] ; [[#Méndez--2010|Méndez and Magaña, 2010]] ; [[#Cavazos--2020|Cavazos et al., 2020]] ). On the other hand, ENSO favours wet conditions in NCA, but its effect is modulated by Pacific Decadal Variability (PDV; [[#Maldonado--2016|Maldonado et al., 2016]] ).

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[[File:e4b6c43bd9d1331ce8736254d0b7c03e IPCC_AR6_WGI_Atlas_Figure_22.png]]

'''Figure Atlas.22''' '''|''' '''Regional changes over land in annual mean surface air temperature and precipitation relative to the 1995–2014 baseline for the reference regions in Central America, the Caribbean and South America (warming since the 1850–1900 pre-industrial baseline is also provided as an offset).''' Barplots in the left panel of each region triplet show the median (dots) and 10th–90th percentile range (bars) across each model ensemble for annual mean temperature changes for four datasets (CMIP5 in intermediate colours; a subset of CMIP5 used to drive CORDEX in light colours; CORDEX overlying the CMIP5 subset with dashed bars; and CMIP6 in solid colours); the first six groups of bars represent the regional warming over two time periods (near-term 2021–2040 and long-term 2081–2100) for three scenarios (SSP1-2.6/RCP2.6, SSP2-4.5/RCP4.5 and SSP5-8.5/RCP8.5), and the remaining bars correspond to four global warming levels (GWL: 1.5°C, 2°C, 3°C and 4°C). The scatter diagrams of temperature against precipitation changes display the median (dots) and 10th–90th percentile ranges for the above four warming levels for December–January–February (DJF; middle panel) and June–July–August (JJA; right panel), respectively; for the CMIP5 subset only the percentile range of temperature is shown, and only for 3°C and 4°C GWLs. Changes are absolute for temperature (in °C) and relative (as %) for precipitation. See [[#Atlas.1.3|Atlas.1.3]] for more details on reference regions ( [[#Iturbide--2020|Iturbide et al., 2020]] ) and [[#Atlas.1.4|Atlas.1.4]] for details on model data selection and processing. The script used to generate this figure is available online ( [[#Iturbide--2021|Iturbide et al., 2021]] ) and similar results can be generated in the Interactive Atlas for flexibly defined seasonal periods. Further details on data sources and processing are available in the chapter data table (Table Atlas.SM.15).

One of the most prominent features of the regional climate is the incidence of tropical cyclones (TCs), which represent an important hazard for almost all the countries of the region between June and November. A detailed assessment is given in Chapter 11.

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===== Atlas.7.1.1.2 Findings From Previous IPCC Assessments =====

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According to AR5 ( [[#Christensen--2013|Christensen et al., 2013]] ), significant positive trends of temperature have been observed in Central America ( ''high confidence'' ), while significant precipitation trends are regionally dependent, especially during the summer. In addition, changes in climate variability and in extreme events have severely affected the region ( ''medium confidence'' ). A decrease in mean precipitation is projected in SCA and NCA. El Niño and La Niña teleconnections are projected to move eastwards in the future ( ''medium confidence'' ), while changes in their effects on other regions, including Central America and the Caribbean is uncertain ( ''medium confidence'' ). There is ''medium confidence'' in projections showing an increase in seasonal mean precipitation on the equatorial flank of the ITCZ affecting parts of Central America and the Caribbean.

In relation to the 1986–2005 baseline period, temperatures are ''very likely'' to increase by the end of the century, even for the RCP2.6 scenario, with changes of more than 5°C in some regions for the RCP8.5 scenario. Precipitation change is projected to vary between +10% and –25% ( ''medium confidence'' ) ( [[#Christensen--2013|Christensen et al., 2013]] ). The SR1.5 ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ) states there is a ''high agreement'' and ''robust evidence'' that at the 1.5°C global warming level the Caribbean region will experience a 0.5°C–1.5°C warming compared to the 1971–2000 baseline period, with greatest warming over larger land masses.

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