Editing IPCC:AR6/WGII/Chapter-14 (section)

== 14.1 Introduction and Point of Departure ==

<div id="h1-2-siblings" class="h1-siblings"></div>

Earth’s climate is currently changing in significant ways as a result of human activities, and future projections indicate continued and possibly accelerating change without reductions in greenhouse gas (GHG) emissions (Gutiérrez et al., 2021; [[#IPCC--2021|IPCC, 2021]] ). Climate change affects human and natural systems; this chapter provides an assessment of present and future climate-change impacts, risks and adaptation for North America, including Mexico, Canada, the USA and coastal waters within the 370-km exclusive economic zone. We do not consider Hawaii and other island territories of the USA in depth as they are assessed in Chapter 15. [https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-14 Chapter 14] assesses evidence from Arctic Canada and Alaska, which is synthesised in [https://www.ipcc.ch/chapter/cross-chapter-paper-6 Cross-Chapter Paper 6] Polar Regions (CCP6).

Evidence from Indigenous knowledge (IK) systems is included in this chapter to assess climate-change risks and solutions in North America following the framing provided in [[IPCC:Wg2:Chapter:Chapter-1|Chapter 1]] Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) ( [[#Abram--2019|Abram et al., 2019]] ) and Special Report on Climate Change and Land (SRCCL) ( [[#IPCC--2019a|IPCC, 2019a]] ). Indigenous contributing authors provided this assessment, reflecting the importance of meaningfully including IK in assessment processes ( [[#Ford--2012|Ford, 2012]] ; [[#Ford--2016|Ford et al., 2016]] ; [[#Hill--2020|Hill et al., 2020]] ). This addition represents an important advancement since AR5 ( [[#IPCC--2013|IPCC, 2013]] ; [[#IPCC--2014|IPCC, 2014]] ).

Our main point of departure was the Fifth Assessment Report (AR5) for WGII ( [[#IPCC--2014|IPCC, 2014]] ). Key findings drawn from the Executive Summary for the North America chapter are summarised in Table 14.1. Subsequent IPCC reports, such as Special Report on Global Warming of 1.5°C (SR1.5) ( [[#Hoegh-Guldberg--2018|Hoegh-Guldberg et al., 2018]] ; [[#IPCC--2018|IPCC, 2018]] ), SROCC ( [[#IPCC--2019b|IPCC, 2019b]] ) and SRCCL ( [[#IPCC--2019a|IPCC, 2019a]] ), also informed the assessment. We additionally incorporated recent national climate assessments of the USA ( [[#USGCRP--2018|USGCRP, 2018]] ) and Canada ( [[#Bush--2019|Bush and Lemmen, 2019]] ; [[#Warren--2021|Warren and Lulham, 2021]] ) as well as the Sixth National Communication of Mexico to the United Nations Framework Convention on Climate Change ( [[#SEMARNAT%20and%20INECC--2018|SEMARNAT and INECC, 2018]] ).

'''Table 14.1 |''' Key findings from AR5 North America chapter ( [[#Romero-Lankao--2014|Romero-Lankao et al., 2014]] b)

{| class="wikitable"
|-
! General topic

! AR5 finding

|-
| rowspan="2"| Climate hazards

| Climate has changed in North America, with some changes attributed to human activities.

|-
| Climate hazards, especially related to heatwaves, heavy precipitation and snowpack, are expected to change in ways that are adverse to natural and human systems.

|-
| Natural ecosystems

| Warming, increasing carbon dioxide (CO 2 ) concentrations, sea level rise (SLR) and climate extremes are stressing ecosystems.

|-
| rowspan="6"| Human systems

| Water resources that are already stressed in many parts of North America are expected to become further stressed by climate change. Current adaptation options can address water supply deficits, but responses to flooding and water quality concerns are more limited.

|-
| Climate change has affected yields of major crops, and projections indicate continued declines, although with variability.

|-
| Extreme climate events have affected human health, although climate-change-related trends and attribution to climate change have not been confirmed.

|-
| Multiple aspects of climate change have affected livelihoods, economic activities, infrastructure and access to services.

|-
| Much infrastructure is vulnerable to extreme weather events, and unless adaptation investments are made, vulnerability to future climate change will persist and increase.

|-
| Most sectors of the North American economy have been affected by and have responded to extreme weather, including hurricanes, flooding and intense rainfall.

|-
| rowspan="2"| Adaptation

| Technological innovation, institutional capacity-building, economic diversification and infrastructure design are adaptations for reducing current climate impacts as well as future risks due to a changing climate.

|-
| North American governments predominantly have undertaken incremental adaptation assessment and planning at the municipal level. Limited proactive, anticipatory adaptation is directed at long-term investment for energy and public infrastructure.

|}

[https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-14 Chapter 14] sections are organised to address themes and content as contained in the IPCC-approved outline for regions. Regional climate changes assessed within North America are keyed to Figure 14.1 using four-letter abbreviations (e.g., CA-ON, US-SE, MX-NW). The assessment addresses recent and future climate for North America, the impacts, risks and adaptations within sectors, key risksacross sectors (KR), the nature of adaptation and sustainable development pathways as well as two additional sections on Indigenous Peoples and perceptions of climate change. Seven boxes are used to highlight topics of interdisciplinary nature while four frequently asked questions (FAQ) were produced in plain language for communication to the public. The chapter utilises the framework as well as designated terms in the standardised process for evaluating and characterising the degree of certainty in assessment findings developed through the expert judgement process ( [[IPCC:Wg2:Chapter:Chapter-1#1.3.4|Section 1.3.4]] ; [[#Mach--2017|Mach et al., 2017]] ). The Glossary [Annex II] provides definitions for terms and concepts used across the report.

<div id="_idContainer007" class="Figure"></div>

[[File:06a913afc3332575f523b2878ba210a9 IPCC_AR6_WGII_Figure_14_002.png]]

'''Figure 14.2 |''' '''Observed and projected climate changes across North America.''' Black boundary lines delineate North American sub-regions (Figure 14.1). Data were extracted from Gutiérrezet al. 2021a via http://interactive-atlas.ipcc.ch/ (WGI Interactive Atlas) ( [[#Gutiérrez--2021b|Gutiérrez et al., 2021b]] ), where dataset details can be found. (A) Recent observations; (B) to (G) are from an ensemble of CMIP6 projections.

'''(A)''' Observed annual mean temperature trend over land for 1980–2015.

'''(B,C)''' Projected change in annual mean temperature over land relative to the 1986–2005 average, associated with 2°C or 4°C global warming.

'''(D,E)''' Like (B,C) but for projected percentage change in annual precipitation.

'''(F,G)''' Like (B,C) but for projected change in number of days per year with maximum temperature &gt;40°C (‘TX40’).

<div id="14.1.1" class="h2-container"></div>

<span id="context"></span>
=== 14.1.1 Context ===

<div id="h2-1-siblings" class="h2-siblings"></div>

With a 2019 total population of over 494 million people (USA 329 million, Mexico 128 million and Canada 37 million), North America comprises 6.4% of the global population. Relative to other countries, North American countries have low population densities per square kilometre (Mexico 64 people, USA 35 people and Canada 4 people) ( [[#United%20Nations--2019|United Nations, 2019]] ). Population projections indicate a steady growth in the three countries, which will exert pressure on consumption and increase risks under climate change ( [[#United%20Nations--2019|United Nations, 2019]] ). North America is also responsible for about a quarter of global greenhouse gas (GHG) emissions. Since 1990, North American GHG emissions have increased by almost 18% ( [[#Ritchie--2020|Ritchie and Roser, 2020]] ), and in 2019 the region was responsible for 5.9 MtCO 2 emissions worldwide ( [[#Friedlingstein--2020|Friedlingstein et al., 2020]] ). In terms of annual CO 2 emissions per capita, in 2019 Canada had 15 metric tons of CO 2 per person (tCO 2 per person), the USA had 16 tCO 2 per person and Mexico had 3.4 tCO 2 per person ( [[#Friedlingstein--2020|Friedlingstein et al., 2020]] ).

<div id="14.2" class="h1-container"></div>

<span id="current-and-future-climate-in-north-america"></span>