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

==== Atlas.9.1.1 Key Features of the Regional Climate ====

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The recent-past climate of North America is characterized by high spatial heterogeneity and by variability at diverse temporal scales. Considering the traditional Köppen-Geiger classification, North America covers all main climate types (see reference region descriptions below). Important geographical features influence local climates over various distances, like the Rocky Mountains through cyclogenesis ( [[#Grise--2013|Grise et al., 2013]] ) and the Great Lakes through lake-effect snowfall ( [[#Wright--2013|Wright et al., 2013]] ). The cryosphere is an important component of the climate system in North America, with fundamental roles for sea ice cover, snow cover and permafrost. The ocean surrounding the continent also influences its climate, with water temperatures strongly influencing hurricane activity which impacts the coasts of eastern Mexico and south-eastern USA ( [[#Walsh--2010|Walsh et al., 2010]] ). Temporal variability is influenced by several large-scale atmospheric modes (Table Atlas.1 and Annex IV) with the North Atlantic Oscillation (NAO) affecting north-eastern USA and eastern Canada precipitation ( [[#Whan--2017|Whan and Zwiers, 2017]] ), and El Niño–Southern Oscillation (ENSO) affecting temperature and precipitation in California, although in a complex and not yet fully understood manner ( [[#Yoon--2015|Yoon et al., 2015]] ; [[#Yeh--2018|Yeh et al., 2018]] ).

The reference regions defined for summarising North America climate change (Figure Atlas.26) include: North-Western North America (NWN), characterized by a sub-Arctic climate with cool summers and rainfall all year round; North-Eastern North America (NEN), which also has a sub-Arctic climate with sections of tundra climate in the far north (these two northern regions are also discussed in Section [[#Atlas.11.2|Atlas.11.2]] , Polar Arctic); Western North America (WNA), which has a complex but mainly cold semi-arid climate; Central North America (CNA) with a mainly continental climate in the northern part of the region and a humid subtropical climate in the southern portion; Eastern North America (ENA) with a humid continental climate in the northern half and a humid subtropical climate to the south; Northern Central America (northern Mexico; NCA), has a temperate climate to the north of the Tropic of Cancer, with marked differences between winter and summer, modulated by the North American Monsoon ( [[#Peel--2007|Peel et al., 2007]] ).

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