3.3.1 Rethinking impact governance for global environmental change

Based on current scientific assessments, including in this report (see Section 1), the likelihood of transgressing one or several ESTPs has been increasing and will likely grow substantially beyond 1.5°C warming, but no tipping process has been set in motion yet. Given that several tipping systems have been destabilised, and could be transgressed in the near term, it is imperative that decision makers start to develop appropriate governance frameworks to address the potential future impacts of ESTPs. If transgressed, ESTPs would severely undermine the pursuit of the SDGs, and reverse recent development progress around the world. The possibly short remaining window of time before the impacts of a tipping process could be felt should be used to increase preparedness, foster community resilience and invest in resources, processes and institutional capacity that would be needed to effectively respond to tipping-point impacts.

Section 2 of this report has assessed the highly diverse expected impacts of ESTPs which are summarised in Table 3.3.1. The assessment shows that ESTPs are very diverse, each with a distinct set of impact types and impact distribution over time and space. Given this diversity, different tipping points (or groups of tipping points) might require distinct kinds of policy responses and impact governance strategies, involving different sets of actors.

Table 3.3.1: Impacts of ESTPs
Overview of impacts and challenges of the various Earth system tipping elements. Please note the anticipated timescales of tipping points unfolding until new equilibrium is reached are best average estimates. GW = global warming; red highlights are temperature thresholds that we are currently approaching, the colouring of the ESTP column signifies the expected severity of the impacts, with darker red shades demonstrating greater severity. We also note the high uncertainty around secondary impacts (see Chapter 2.3 and 2.4)

Earth system tipping point Sea level rise/coastal erosion Extreme weather eventsFeedback on global warmingWater shortagesChanges in precipitationRegional temperature changeEcosystem changeRelease of pollutantsInfrastructure damageFood securityTriggering other ESTPsSecondary societal impacts Thresholds, timescales & spatial extent
Cryosphere
Greenland Ice Sheet collapseUp to 7m sea level rise overall over 1000s years, together with WAIS potentially up to c. 2m by 2100 [IPCC AR6 WG1 Ch9], affecting 480 million peopleMinor impact (local circulation changes)Minor impact (~0.1°C over 1000s y.)Water shortages due to coastal salinisationLocal impact possible effect on tropical monsoons via AMOC disruption [Defrance et al., 2017])Regional amplification of warmingCoastal areas, new exposed land in GreenlandMinor (some pollutants trapped in ice)Threat to coastal power plants,Destruction of coastal built environmentSalinisation impacting agriculture & food securityImpact on AMOC/SPG as tipping may be reached sooner (but timescales unclear)Displacement of coastal area popula- tions, conflicts over water etc, financial crises (stranded assets)0.8-3°C GW,
long period (1000s y.),

global impacts
Arctic Sea Ice loss (not considered a tipping system in this report)Increased coastal inundation and erosion from larger waves with more open oceanUncertain; possible contribution to increase in extreme weather events (e.g. Extreme European snowfall)Uncertain, possibly ~+0.25°C for summer sea ice loss & ~+0.6 °C for winter sea ice loss, included in model projectionsNo impactLocal impact with more open water causing increased evaporation and increased precipitation, shift from snowfall to rainfallRegional amplification of warming (particularly Arctic and Northern Hemisphere)Details uncertain, but loss of sea ice is expected to substantially affect the marine Arctic ecosystems; impact on land ecosystems unclearChanges in pollutant & microplastic transport in the ice-free Arctic; increased contaminant input from the Arctic coastal erosionPossible damage through extreme weather events and through increased coastal erosionExtreme weather events could destroy harvests, disruption of traditional Indigenous food systemsAmplifies regional warming over Greenland, AMOC/SPG, boreal forests & permafrost; coastal permafrost loss acceleratedCoastal erosion, loss of Indigenous ways of life, & possible extreme weather events contributing to conflicts, (temporary) displacement, anomie etcNA for tipping;
4.5-8.7°C GW for gradual winter sea ice loss in models [McKay et al., 2022],

fast (20 y.),

global impacts
Barents Sea Ice loss (not a tipping system, low confidence)No impactUnclear; potential contribution to increase in extreme weather events (Europe)Negligible impactNo impactPossible regional impacts in EuropeLocal warmingLocal ecosystems (marine & bordering land)Unclear, but changes in circulation can affect pollution redistribution (e.g. of mercury)Possible damage through extreme weather eventsPossible extreme weather events could destroy harvestsSmall impact on AMOC & regional boreal forestsPossible extreme weather events contributing to conflicts, (temporary) displacement, anomie etc NA for tipping, (but 1.5-1.7°C GW in some models) [McKay et al., 2022],

fast (25 y.),

regional & global impacts
Permafrost thawAbrupt thaw can amplify coastal erosionMinor impact (can lead to increased lightning strikes and wildfire ignition)Release of greenhouse gases, driving further global warmingComplex changes to the local water table via abrupt drainage, thermokarst lake formationMinor impactNo impactBoreal/tundra ecosystemsRelease of contaminants such as mercury into the environmentDisrupts travel in Arctic and isolates settlementsBuilt infrastructure damage and destructionImpact on permafrost-agroecosystems and community-level food storage in frozen underground cellarsImportant but uncertain impact on Boreal forest dieback/expansion tipping pointsAnomie among regional population inhabiting the areas, due to livelihood and cultural loss   NA for tipping, abrupt thaw more common from 1.5°C GW [McKay et al., 2022],

medium-term (~200 y.) regional & global impacts
West Antarctic Ice Sheet collapse3-5m sea level rise overall over 100s-1000s y, together with GrIS potentially up to c. 2m by 2100 [IPCC AR6 WG1 Ch9], affecting 480 million peopleMinor impact; possible massive iceberg release events in Southern OceanMinor impact (potentially ~0.05°C over 100s-1000s y.)Water shortages due to sea level-induced coastal salinisationLocal impactRegional warming amplificationCoastal area, new exposed islands and seas in West AntarcticaNo impactThreat to coastal power plants,Destruction of coastal built environmentSalinisation impacting agriculture & food securityMay affect East Antarctic ice sheets & possibly Southern Ocean overturning circulation Displacement of coastal area popula- tions, conflicts over water etc., financial crises (stranded assets) 1-3°C GW,

long period (2000 y.),

global impacts
East Antarctic IceSheet (marine & non-marine) collapseUp to 53m total sea level rise potential; sea level rise of several metres possible over 100s-1000s of yearsMinor impact; possible massive iceberg release events in Southern OceanAdditional warming of potentially ~0.6°C over 10,000s y.Water shortages due to coastal salinisationLocal impactRegional warming amplificationCoastal areas, new exposed land and seas in East AntarcticaNo impactThreat to coastal power plants,Destruction of coastal built environmentSalinisation impacting agriculture & food securityCollapse of ice sheet in marine basins could accelerate land-based ice sheet tipping & Southern Ocean overturning circulationDisplacement of coastal area populations, conflicts over water etc, financial crises (stranded assets) 2-6°C GW marine & 6-10°C GW non-marine, very long period (10,000 y.), global impacts
Extrapolar glacier retreatUp to 0.2m sea level riseNo impactMinor impact (potentially ~0.08°C)Impact of freshwater supply from meltwater in many regions of the world (e.g. Central Asia, Europe) leading to water shortagesNo impactLocalised warming amplificationChanges in surrounding montane & downstream ecosystem, new land exposedMinor (some pollutants trapped in ice)Destabilisa-
tion of valley sides could lead to landslides, glacier collapse events can cause floods/mud-
slides
Water shortages impacting agriculture & food securityNo impactConflicts over water etc, anomie due to livelihood and cultural loss Regionally variable (but potentially widespread from ~2°C GW, e.g. in Europe) [McKay et al., 2022],

medium-term (200 y.),

regional impacts
Ocean/Atmosphere Circulation
AMOC collapse Regional sea level changes (fall in convection region & North European Shelf seas, rise further south)Shift in jet stream and storm tracks affecting weather patterns in Europe, potential increase in extreme weather events, e.g. cold winters in Europe, south-ward hurricanes shiftPartial & temporary counteraction of global warmingSouthward shift in ITCZ leading to drying in the Sahel and Southern Asia; Some models project drying in parts of the Amazon  Summer monsoon weakening and shifts in Africa and AsiaUp to 10°C cooling in North Atlantic and 3°C cooling in Northern Europe / Eastern Canada, warming amplification in Southern HemisphereDrastic shifts in many ecosystems on land and in the sea around the world, e.g. Amazon dryingAffects dust aerosols via monsoon disruption in those regions; ocean circulation changes can affect pollutant pathwaysShifted temperatures/precipitation & weather patterns/extremes no longer matching infrastructure tolerance rangesThreat to food security because of impacts on marine life (reduction of plankton),changes in precipitation severely impacting agriculture (particularly wheat and maize) & food security (particularly in Europe)Warming amplification in Southern Hemisphere accelerating Antarctic Ice Sheet melt and coral bleaching, Amazon drying; monsoon (African and Asian) shifts acceleratedConflicts over food and water, displacement from uninhabitable areas, anomie, financial crises, etc NA in this report, 1.4-8°C GW elsewhere (but low confidence) McKay et al., 2022],

Possibly relatively fast (~50 y. To centuries)

Complex global impacts with strong regional differences
Labrador-
Irminger Seas Convection (Subpolar Gyre) collapse
20-30cm sea level rise along North-East seaboard of North AmericaSimilar to AMOC but possibly smaller impact, e.g. amplified cold winter blocking events in Europe & increase in summer heat wave frequency Similar to AMOC but magnitude of impact is unclearSimilar to AMOC but possibly smaller impact  Similar to AMOC but impact is not completely clearUp to 2-3°C cooling in North Atlantic, global warming counteracted in Northern Europe / Eastern CanadaLarge changes in ecosystems in affected regions (e.g. reduced North Atlantic productivity, regional ocean acidification, deoxygenation)Impact unclear, but could be similar to AMOCSimilar to AMOC but smaller impactMajor disruptions of agriculture in Northern Europe and Sahel, impacting food securitySimilar to AMOC but impact is not completely clear, potentially a large change in N. Atlantic ecosystemsConflicts over food and water, displacement from uninhabitable areas, anomie, financial crises, etc1.1-3.8°C GW,

very fast (10 years),

regional impacts
Monsoon shifts (intensification or collapse, e.g. South Asian, West African, South American)No impactMonsoon intensity & extremes projected to increase with warming, or strong drop due to aerosol-induced collapseNo ImpactShifted precipitation may lead to water shortagesDrastic precipitation changesChange in tropical and subtropical climates  Change in vegetation and ecosystems in general relying on the monsoonChanges to where monsoons redistribute air pollutionMore intense monsoons overwhelming current infrastructure; monsoon collapse leaving infrastructure mal-adaptedChanged vegetation, agriculture dependent on monsoon rainfall will impact livelihoods and food securityWAM could drive Sahel greening, SAM could affect AmazonConflicts over food and water, displacement from uninhabitable areas, anomie, etc Interhemispheric AOD asymmetry >0.15, AMOC collapse, Amazon dieback; 2-3.5°C for WAM in some models McKay et al., 2022],

relatively fast (50 y.),

regional impacts
Biosphere
Amazon rainforest diebackNo impactIncreasing extreme weather events (e.g. wet bulb spikes, wildfires) in regionAdditional global warming (0.1-0.2°C, depending on extent)Decreased precipitation may lead to water shortagesDeclining regional precipitation in Amazon and Southern Cone regionOver 1°C extra regional warmingParts of rainforest (particularly in South & East) shift to degraded forest or savannahSmoke from increased wildfiresMinor impactDecreased precipitation would impact agricultural belt of Brazil and into Southern ConeAmplified global warming, bringing other warming thresholds closerConflicts over food and water, displacement from uninhabitable areas, anomie, 2-6°C GW (without deforestation) ~20-40% deforestation,

relatively fast (100 y.),

regional and global impacts
Boreal Forest Southern dieback / Northern expansionNo impactIncreasing extreme weather events (e.g. wildfires)Complex effects – dieback releases carbon but reduces albedo, expansion vice versaMay change with evapotranspiration-induced weather pattern shiftsChanges to evapotranspiration likely to shift regional weather patternsRegional changes due to changes in land albedoShift to open, steppe/prairie-like ecosystems in south, tundra afforestation in north  Smoke from wildfiresMinor impactDisruption of traditional Indigenous food systemsComplex interplay with permafrost thaw, northern expansion adds to Arctic warming; drives lake browningAnomie among regional population inhabiting the areas, due to livelihood and cultural loss 1.4-5°C GW southern dieback, 1.5-7.2°C GW northern expansion,

relatively fast (100 y.), regional impacts
Warm-water coral reef die-offDecreased coastal protection (coastal erosion)Increased vulnerability to extreme weather eventsLimited impact on GW until very long termNo impactMinor impactsMinor impactTropical and subtropical coral reefs mostly die-off, resulting in great biodiversity lossNo impactLoss of coastal protection services may require engineered replacementsImpact on marine food web, Impact on 500 million livelihoods and food securityPossible interaction with nearby mangroves and seagrass die-off and marine regime shiftsConflicts over decreasing fish stock, anomie because of livelihood and culture loss, etc. 1-1.5°C GW, plus non-climate thresholds,

very fast (10 years),

regional and global impacts
Coastal ecosystem regime shifts (mangroves/seagrass)Decreased coastal protection (coastal erosion)Increased vulnerability to extreme weather eventsLoss of C sink and release of GHGs, but small impact at global scaleReduced coastal protection can allow greater seawater ingress, with storms and, aquifer salinisationMinor impactNo impactMany mangroves & seagrass ecosystems die-off, resulting in great biodiversity & ecosystem services lossNo impactLoss of coastal protection services may require engineered replacementsImpact on marine food web, fishery and food securityPossible interaction with nearby coral reef die-off and marine regime shiftsConflicts over decreasing fish stock, anomie because of livelihood and culture loss, etc ~1.5oC GW, but highly uncertain and spatially variable; Regional impacts
Savannahs & grasslands (ecosystem regime shift)No impactGreater vulnerability to drought or extremely high rainfallShifts in carbon storage – some GHG release possible (but globally small)Greater groundwater depletion (with shrub encroach-
ment)
Regional precipitation changesComplex regional temperature change from changes to albedo and eco-
hydrology
Change in vegetation, leading to biodiversity loss, reduced fires with shrub encroachmentNo impactMinor impactLoss of grazing lands will impact livelihoods and food securityPossible interaction with nearby dryland and tropical forest tipping pointsConflicts over food and water, displacement from uninhabitable areas, anomie, etc Regionally variable rainfall & fire thresholds,

regional impacts 
Temperate forestsdiebackNo impactIncreased wildfiresCarbon emissions (amplifying global warming)Less atmospheric water supply and groundwater rechargeChanges to evapotranspiration likely to shift regional weather patternsRegional warming in summer due to less evaporative cooling and cloud coverChange in forest ecosystems leading to biodiversity lossSmoke from wildfiresMinor impactLoss of indirect ecosystem services (e.g. pollinators, groundwater recharge)Possible impacts on nearby boreal forestAnomie because of loss of livelihoods and cultural lossThresholds unknown

regional impacts
Drylands (ecosystem regime shift)No impactGreater vulnerability to drought or extremely high rainfallShifts in carbon storage – some GHG release possible (but globally small)Aridification may lead to water shortage, groundwater depletion with shrub encroach-
ment
Regional precipitation changes, leading to aridification in some areas  Complex regional temperature change from changes to albedo and eco-
hydrology
Aridification/desertification or shrub encroachment, leading to biodiversity lossNo impactMinor impactAridification/desertification or shrub encroachment will impact agriculture and food securityPossible interaction with nearby savannah and tropical forest tipping pointsConflict over water and land, displacement from uninhabitable areas, anomie, etc Aridity indices (0.2, 0.3, 0.45) for aridification,

regional impacts
Freshwater lakes (eutrophication-driven anoxia)No impactNo impactIncreased GHG emissions (reduced for salinisation) could impact GWWater quality decline could lead to water shortagesMinor impactMinor impactLake ecosystem regime shift, biodiversity lossSome algae blooms are toxicMinor impactsFreshwater fish stock decline could impact food security; water shortages could impact agriculture and food securityNo impactConflict over water, anomie due to livelihood and cultural loss, etcVariable for each lake, but higher risk beyond 50-100 mgP/m3 and 2.5 (1–4) mg N/l

Impacts in lake regions, with great regional differences in impact severity
Marine environment regime shiftMinor impact (loss of kelp forests could reduce coastal protection in some places)No impactMajor changes in ocean productivity, carbon sinks & ocean biogeochemistry could have moderate impact on GWNo impactMinor impactMinor impactBiodiversity loss from trophic cascades and regime shiftsCoastal eutrophication can lead to e.g. toxic ‘red tides’Minor impactFish stock collapse could impact food securityMinor impact via reduced carbon sink amplifying GWConflicts over decreasing fish stock, anomie because of livelihood and culture loss, etc Multiple drivers with highly localised thresholds;

global and regional impacts; multi-decadal to centennial timescales
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