Title page
Contents
Summary 4
01. Introduction 6
02. Emissions trajectory and risks 8
03. Direct climate impacts 11
3.1. Approach: how to understand the impacts presented 11
3.2. Heat, productivity and health 15
3.3. Food security 22
3.4. Water security 30
04. Cascading systemic risks 37
4.1. Vulnerabilities mediating cascading risks 40
4.2. National and international security 41
4.3. Economic and trade disruption 42
4.4. Migration pressures 43
4.5. Food security 44
4.6. Health crises 45
4.7. Energy security 46
05. Conclusions 48
About the authors 50
Acknowledgments 51
Table 1. Cropland areas across crop types and continents. Highlighted entries are shown in Figure 13 28
Figure 1a. Energy sector and industrial process CO₂ emissions to 2040, based on indicator trends 9
Figure 1b. Warming probability in different scenarios, in 2100 9
Figure 2. Number of people exposed to heat stress above the risks to workability and survivability thresholds at a given change in global mean surface temperature relative to pre-industrial levels 16
Figure 3a. Global population experiencing a heatwave that exceeds the 98th percentile of the reference period (1981-2010) for two or more consecutive days per year 17
Figure 3b. Global population experiencing a major heatwave that exceeds the 99th percentile of the reference period (1981-2010) for four or more consecutive days per year 17
Figure 4. Proportion of regional populations experiencing major heatwaves, in 2040 18
Figure 5. Populations within African regions and the Middle East experiencing heatwaves and major heatwaves 19
Figure 6. Populations within Asia and Australasia experiencing heatwaves and major heatwaves 20
Figure 7. Populations within Europe experiencing heatwaves and major heatwaves 21
Figure 8. Populations within North, Central and South America experiencing heatwaves and major heatwaves 21
Figure 9a. Proportion of global cropland experiencing severe drought of three months or more per year 23
Figure 9b. Proportion of regional cropland exposed to severe drought, in 2050 24
Figure 10a. Proportion of global winter wheat crop area experiencing damaging hot spells 25
Figure 10b. Proportion of global rice crop area experiencing damaging hot spells 25
Figure 11. Proportion of global crop areas with reductions in crop duration periods of at least 10 days, by crop type 26
Figure 12. Proportion of continental cropland experiencing severe drought of three months or more 27
Figure 13. Proportion of the largest areas, for different crops per continent (across five crop types), with reductions in crop duration periods of at least 10 days, and experiencing damaging hot spells 29
Figure 14a. Global population experiencing a drought of at least six months with 12-month accumulated Standardized Runoff Index of less than -1.5 31
Figure 14b. Proportion of regional populations experiencing drought, in 2040 32
Figure 15. Populations experiencing a drought of at least six months with 12-month accumulated Standardized Runoff Index of less than -1.5, by continent 33
Figure 16. Regions of increasing water stress (demand relative to supply) in 2040, relative to 2019 34
Figure 17. Committed sea level rise as a function of long-term global temperature increase 35
Figure 18. Populations in selected regions likely to experience coastal and river flooding 36
Figure 19. Summary diagram of the major systemic risk dynamics identified by an expert elicitation process 38
Figure 20. Experts' assessments of systemic cascading climate risks that are likely to lead to greater national and international insecurity 41
Figure 21. Experts' assessments of systemic cascading climate risks that are likely to lead to economic and trade disruptions 43
Figure 22. Experts' assessments of systemic cascading climate risks that are likely to lead to migration pressures 44
Figure 23. Experts' assessments of systemic cascading climate risks that are likely to lead to food insecurity 45
Figure 24. Experts' assessments of systemic cascading climate risks that are likely to lead to health crises 46
Figure 25. Experts' assessments of systemic cascading climate risks that are likely to lead to energy insecurity 47
Boxes
Box 1. A plausible worst-case scenario 10
Box 2. Tipping points 14
Box 3. Extreme weather events often trigger cascading impacts 39