Editing IPCC:AR6/SRCCL/SPM (section)

== Box SPM.1 Shared Socio-economic Pathways (SSPs) ==

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In this report the implications of future socio-economic development on climate change mitigation, adaptation and land-use are explored using shared socio-economic pathways (SSPs). The SSPs span a range of challenges to climate change mitigation and adaptation.

* SSP1 includes a peak and decline in population (~7 billion in 2100), high income and reduced inequalities, effective land-use regulation, less resource intensive consumption, including food produced in low-GHG emission systems and lower food waste, free trade and environmentally-friendly technologies and lifestyles. Relative to other pathways, SSP1 has low challenges to mitigation and low challenges to adaptation (i.e., high adaptive capacity)
* SSP2 includes medium population growth (~9 billion in 2100), medium income, technological progress, production and consumption patterns are a continuation of past trends, and only a gradual reduction in inequality occurs. Relative to other pathways, SSP2 has medium challenges to mitigation and medium challenges to adaptation (i.e., medium adaptive capacity).
* SSP3 includes high population growth (~13 billion in 2100), low income and continued inequalities, material-intensive consumption and production, barriers to trade, and slow rates of technological change. Relative to other pathways, SSP3 has high challenges to mitigation and high challenges to adaptation (i.e., low adaptive capacity).
* SSP4 includes medium population growth (~9 billion in 2100), medium income, but significant inequality within and across regions. Relative to other pathways, SSP4 has low challenges to mitigation, but high challenges to adaptation (i.e., low adaptive capacity).
* SSP5 includes a peak and decline in population (~7 billion in 2100), high income, reduced inequalities, and free trade. This pathway includes resource-intensive production, consumption and lifestyles. Relative to other pathways, SSP5 has high challenges to mitigation, but low challenges to adaptation (i.e., high adaptive capacity).
* The SSPs can be combined with Representative Concentration Pathways (RCPs) which imply different levels of mitigation, with implications for adaptation. Therefore, SSPs can be consistent with different levels of global mean surface temperature rise as projected by different SSP-RCP combinations. However, some SSP-RCP combinations are not possible; for instance RCP2.6 and lower levels of future global mean surface temperature rise (e.g., 1.5ºC) are not possible in SSP3 in modelled pathways. {1.2.2, 6.1.4, Cross-Chapter Box 1 in Chapter 1, Cross-Chapter Box 9 in Chapter 6}

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'''Figure SPM.2'''

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'''Risks to land-related human systems and ecosystems from global climate change, socio-economic development and mitigation choices in terrestrial ecosystems As in previous IPCC reports the literature was used to make expert judgements to assess the levels of global warming at which levels of risk are undetectable, moderate, high or very high, as described further in […]'''
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'''Risks to land-related human systems and ecosystems from global climate change, socio-economic development and mitigation choices in terrestrial ecosystems''' As in previous IPCC reports the literature was used to make expert judgements to assess the levels of global warming at which levels of risk are undetectable, moderate, high or very high, as described further in Chapter 7 and other parts of the underlying report. The Figure indicates assessed risks at approximate warming levels which may be influenced by a variety of factors, including adaptation responses. The assessment considers adaptive capacity consistent with the SSP pathways as described below. '''Panel A:''' Risks to selected elements of the land system as a function of global mean surface temperature {2.1, Box 2.1, 3.5, 3.7.1.1, 4.4.1.1, 4.4.1.2, 4.4.1.3, 5.2.2, 5.2.3, 5.2.4, 5.2.5, 7.2, 7.3, Table SM7.1}. Links to broader systems are illustrative and not intended to be comprehensive. Risk levels are estimated assuming medium exposure and vulnerability driven by moderate trends in socioeconomic conditions broadly consistent with an SSP2 pathway. {Table SM7.4} '''Panel B:''' Risks associated with desertification, land degradation and food security due to climate change and patterns of socio-economic development. Increasing risks associated with desertification include population exposed and vulnerable to water scarcity in drylands. Risks related to land degradation include increased habitat degradation, population exposed to wildfire and floods and costs of floods. Risks to food security include availability and access to food, including population at risk of hunger, food price increases and increases in disability adjusted life years attributable due to childhood underweight. Risks are assessed for two contrasted socio-economic pathways (SSP1 and SSP3 {Box SPM.1}) excluding the effects of targeted mitigation policies. {3.5, 4.2.1.2, 5.2.2, 5.2.3, 5.2.4, 5.2.5, 6.1.4, 7.2, Table SM7.5} Risks are not indicated beyond 3°C because SSP1 does not exceed this level of temperature change. '''All panels:''' As part of the assessment, literature was compiled and data extracted into a summary table. A formal expert elicitation protocol (based on modified-Delphi technique and the Sheffield Elicitation Framework), was followed to identify risk transition thresholds. This included a multi-round elicitation process with two rounds of independent anonymous threshold judgement, and a final consensus discussion. Further information on methods and underlying literature can be found in Chapter 7 Supplementary Material.

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'''A.5        '''<br />
'''Climate change creates additional stresses on land, exacerbating existing risks to livelihoods, biodiversity, human and ecosystem health, infrastructure, and food systems ( ''high confidence'' ). Increasing impacts on land are projected under all future GHG emission scenarios ( ''high confidenc'' e). Some regions will face higher risks, while some regions will face risks previously not anticipated ( ''high confidenc'' e). Cascading risks with impacts on multiple systems and sectors also vary across regions ( ''high confidence'' ). (Figure SPM.2) {2.2, 3.5, 4.2, 4.4, 4.7, 5.1, 5.2, 5.8, 6.1, 7.2, 7.3, Cross-Chapter Box 9 in Chapter 6}'''

A.5.1<br />
With increasing warming, the frequency, intensity and duration of heat related events including heatwaves are projected to continue to increase through the 21 <sup>st</sup> century ( ''high confidence'' ). The frequency and intensity of droughts are projected to increase particularly in the Mediterranean region and southern Africa ( ''medium confidence'' ). The frequency and intensity of extreme rainfall events are projected to increase in many regions ( ''high confidence'' ). {2.2.5, 3.5.1, 4.2.3, 5.2}

A.5.2<br />
With increasing warming, climate zones are projected to further shift poleward in the middle and high latitudes ( ''high confidence'' ). In high-latitude regions, warming is projected to increase disturbance in boreal forests, including drought, wildfire, and pest outbreaks ( ''high confidence'' ). In tropical regions, under medium and high GHG emissions scenarios, warming is projected to result in the emergence of unprecedented  <sup>[[#fn:29|29]]</sup> climatic conditions by the mid to late 21 <sup>st</sup> century ( ''medium confidence'' ). {2.2.4, 2.2.5, 2.5.3, 4.3.2}

A.5.3<br />
Current levels of global warming are associated with moderate risks from increased dryland water scarcity, soil erosion, vegetation loss, wildfire damage, permafrost thawing, coastal degradation and tropical crop yield decline ( ''high confidence'' ). Risks, including cascading risks, are projected to become increasingly severe with increasing temperatures. At around 1.5°C of global warming the risks from dryland water scarcity, wildfire damage, permafrost degradation and food supply instabilities are projected to be high ( ''medium confidence'' ). At around 2°C of global warming the risk from permafrost degradation and food supply instabilities are projected to be very high ( ''medium confidence'' ). Additionally, at around 3°C of global warming risk from vegetation loss, wildfire damage, and dryland water scarcity are also projected to be very high ( ''medium confidence'' ). Risks from droughts, water stress, heat related events such as heatwaves and habitat degradation simultaneously increase between 1.5°C and 3°C warming ( ''low confidence'' ). (Figure SPM.2) {7.2.2, Cross-Chapter Box 9 in Chapter 6, Chapter 7 Supplementary Material}

A.5.4<br />
The stability of food supply  <sup>[[#fn:30|30]]</sup> is projected to decrease as the magnitude and frequency of extreme weather events that disrupt food chains increases ( ''high confidence'' ). Increased atmospheric CO <sub>2</sub> levels can also lower the nutritional quality of crops ( ''high confidence'' ). In SSP2, global crop and economic models project a median increase of 7.6% (range of 1–23%) in cereal prices in 2050 due to climate change (RCP6.0), leading to higher food prices and increased risk of food insecurity and hunger ( ''medium confidence'' ). The most vulnerable people will be more severely affected ( ''high confidence'' ). {5.2.3, 5.2.4, 5.2.5, 5.8.1, 7.2.2.2, 7.3.1}

A.5.5<br />
In drylands, climate change and desertification are projected to cause reductions in crop and livestock productivity ( ''high confidence'' ), modify the plant species mix and reduce biodiversity ( ''medium confidence'' ). Under SSP2, the dryland population vulnerable to water stress, drought intensity and habitat degradation is projected to reach 178 million people by 2050 at 1.5°C warming, increasing to 220 million people at 2°C warming, and 277 million people at 3°C warming ( ''low confidence'' ). {3.5.1, 3.5.2, 3.7.3}

A.5.6<br />
Asia and Africa  <sup>[[#fn:31|31]]</sup> are projected to have the highest number of people vulnerable to increased desertification. North America, South America, Mediterranean, southern Africa and central Asia may be increasingly affected by wildfire. The tropics and subtropics are projected to be most vulnerable to crop yield decline. Land degradation resulting from the combination of sea-level rise and more intense cyclones is projected to jeopardise lives and livelihoods in cyclone prone areas ( ''very high confidence'' ).  Within populations, women, the young, elderly and poor are most at risk ( ''high confidence'' ). {3.5.1, 3.5.2, 4.4, Table 4.1, 5.2.2, 7.2.2, Cross-Chapter Box 3 in Chapter 2}

A.5.7<br />
Changes in climate can amplify environmentally induced migration both within countries and across borders ( ''medium confidence'' ), reflecting multiple drivers of mobility and available adaptation measures ( ''high confidence'' ). Extreme weather and climate or slow-onset events may lead to increased displacement, disrupted food chains, threatened livelihoods ( ''high confidence'' ), and contribute to exacerbated stresses for conflict ( ''medium confidence'' ). {3.4.2, 4.7.3, 5.2.3, 5.2.4, 5.2.5, 5.8.2, 7.2.2, 7.3.1}

A.5.8<br />
Unsustainable land management has led to negative economic impacts ( ''high confidence'' ). Climate change is projected to exacerbate these negative economic impacts ( ''high confidence'' ). {4.3.1, 4.4.1, 4.7, 4.8.5, 4.8.6, 4.9.6, 4.9.7, 4.9.8, 5.2, 5.8.1, 7.3.4, 7.6.1, Cross-Chapter Box 10 in Chapter 7}

'''A.6        '''<br />
'''The level of risk posed by climate change depends both on the level of warming and on how population, consumption, production, technological development, and land management patterns evolve ( ''high confidence'' ). Pathways with higher demand for food, feed, and water, more resource-intensive consumption and production, and more limited technological improvements in agriculture yields result in higher risks from water scarcity in drylands, land degradation, and food insecurity ( ''high confidence'' ). (Figure SPM.2b) {5.1.4, 5.2.3, 6.1.4, 7.2, Cross-Chapter Box 9 in Chapter 6}'''

A.6.1<br />
Projected increases in population and income, combined with changes in consumption patterns, result in increased demand for food, feed, and water in 2050 in all SSPs ( ''high confidence'' ). These changes, combined with land management practices, have implications for land-use change, food insecurity, water scarcity, terrestrial GHG emissions, carbon sequestration potential, and biodiversity ( ''high confidence'' ). Development pathways in which incomes increase and the demand for land conversion is reduced, either through reduced agricultural demand or improved productivity, can lead to reductions in food insecurity ( ''high confidence'' ). All assessed future socio-economic pathways result in increases in water demand and water scarcity ( ''high confidence'' ). SSPs with greater cropland expansion result in larger declines in biodiversity ( ''high confidence'' ). {6.1.4}

A.6.2<br />
Risks related to water scarcity in drylands are lower in pathways with low population growth, less increase in water demand, and high adaptive capacity, as in SSP1 {Box SPM.1}. In these scenarios the risk from water scarcity in drylands is moderate even at global warming of 3°C ( ''low confidence'' ). By contrast, risks related to water scarcity in drylands are greater for pathways with high population growth, high vulnerability, higher water demand, and low adaptive capacity, such as SSP3. In SSP3 the transition from moderate to high risk occurs between 1.2°C and 1.5°C ( ''medium confidence'' ). (Figure SPM.2b, Box SPM.1) {7.2}

A.6.3<br />
Risks related to climate change driven land degradation are higher in pathways with a higher population, increased land-use change, low adaptive capacity and other barriers to adaptation (e.g., SSP3). These scenarios result in more people exposed to ecosystem degradation, fire, and coastal flooding ( ''medium confidence'' ). For land degradation, the projected transition from moderate to high risk occurs for global warming between 1.8°C and 2.8°C in SSP1 ( ''low confidence'' ) and between 1.4°C and 2°C in SSP3 ( ''medium confidence'' ). The projected transition from high to very high risk occurs between 2.2°C and 2.8°C for SSP3 ( ''medium confidence'' ). (Figure SPM.2b) {4.4, 7.2}

A.6.4<br />
Risks related to food security are greater in pathways with lower income, increased food demand, increased food prices resulting from competition for land, more limited trade, and other challenges to adaptation (e.g., SSP3) ( ''high confidence'' ). For food security, the transition from moderate to high risk occurs for global warming between 2.5°C and 3.5°C in SSP1 ( ''medium confidence'' ) and between 1.3°C and 1.7°C in SSP3 ( ''medium confidence'' ). The transition from high to very high risk occurs between 2°C and 2.7°C for SSP3 ( ''medium confidence'' ). (Figure SPM.2b) {7.2}

A.6.5<br />
Urban expansion is projected to lead to conversion of cropland leading to losses in food production ( ''high confidence'' ). This can result in additional risks to the food system. Strategies for reducing these impacts can include urban and peri-urban food production and management of urban expansion, as well as urban green infrastructure that can reduce climate risks in cities   <sup>[[#fn:32|32]]</sup> ( ''high confidence'' ). (Figure SPM.3) {4.9.1, 5.5, 5.6, 6.3, 6.4, 7.5.6}

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