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 events	Feedback on global warming	Water shortages	Changes in precipitation	Regional temperature change	Ecosystem change	Release of pollutants	Infrastructure damage	Food security	Triggering other ESTPs	Secondary societal impacts	Thresholds, timescales & spatial extent
Cryosphere
Greenland Ice Sheet collapse	Up 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 people	Minor impact (local circulation changes)	Minor impact (~0.1°C over 1000s y.)	Water shortages due to coastal salinisation	Local impact possible effect on tropical monsoons via AMOC disruption [Defrance et al., 2017])	Regional amplification of warming	Coastal areas, new exposed land in Greenland	Minor (some pollutants trapped in ice)	Threat to coastal power plants,Destruction of coastal built environment	Salinisation impacting agriculture & food security	Impact 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 ocean	Uncertain; 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 projections	No impact	Local impact with more open water causing increased evaporation and increased precipitation, shift from snowfall to rainfall	Regional 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 unclear	Changes in pollutant & microplastic transport in the ice-free Arctic; increased contaminant input from the Arctic coastal erosion	Possible damage through extreme weather events and through increased coastal erosion	Extreme weather events could destroy harvests, disruption of traditional Indigenous food systems	Amplifies regional warming over Greenland, AMOC/SPG, boreal forests & permafrost; coastal permafrost loss accelerated	Coastal erosion, loss of Indigenous ways of life, & possible extreme weather events contributing to conflicts, (temporary) displacement, anomie etc	NA 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 impact	Unclear; potential contribution to increase in extreme weather events (Europe)	Negligible impact	No impact	Possible regional impacts in Europe	Local warming	Local ecosystems (marine & bordering land)	Unclear, but changes in circulation can affect pollution redistribution (e.g. of mercury)	Possible damage through extreme weather events	Possible extreme weather events could destroy harvests	Small impact on AMOC & regional boreal forests	Possible 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 thaw	Abrupt thaw can amplify coastal erosion	Minor impact (can lead to increased lightning strikes and wildfire ignition)	Release of greenhouse gases, driving further global warming	Complex changes to the local water table via abrupt drainage, thermokarst lake formation	Minor impact	No impact	Boreal/tundra ecosystems	Release of contaminants such as mercury into the environment	Disrupts travel in Arctic and isolates settlementsBuilt infrastructure damage and destruction	Impact on permafrost-agroecosystems and community-level food storage in frozen underground cellars	Important but uncertain impact on Boreal forest dieback/expansion tipping points	Anomie 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 collapse	3-5m 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 people	Minor impact; possible massive iceberg release events in Southern Ocean	Minor impact (potentially ~0.05°C over 100s-1000s y.)	Water shortages due to sea level-induced coastal salinisation	Local impact	Regional warming amplification	Coastal area, new exposed islands and seas in West Antarctica	No impact	Threat to coastal power plants,Destruction of coastal built environment	Salinisation impacting agriculture & food security	May 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) collapse	Up to 53m total sea level rise potential; sea level rise of several metres possible over 100s-1000s of years	Minor impact; possible massive iceberg release events in Southern Ocean	Additional warming of potentially ~0.6°C over 10,000s y.	Water shortages due to coastal salinisation	Local impact	Regional warming amplification	Coastal areas, new exposed land and seas in East Antarctica	No impact	Threat to coastal power plants,Destruction of coastal built environment	Salinisation impacting agriculture & food security	Collapse of ice sheet in marine basins could accelerate land-based ice sheet tipping & Southern Ocean overturning circulation	Displacement 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 retreat	Up to 0.2m sea level rise	No impact	Minor 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 shortages	No impact	Localised warming amplification	Changes in surrounding montane & downstream ecosystem, new land exposed	Minor (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 security	No impact	Conflicts 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 shift	Partial & temporary counteraction of global warming	Southward 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 Asia	Up to 10°C cooling in North Atlantic and 3°C cooling in Northern Europe / Eastern Canada, warming amplification in Southern Hemisphere	Drastic shifts in many ecosystems on land and in the sea around the world, e.g. Amazon drying	Affects dust aerosols via monsoon disruption in those regions; ocean circulation changes can affect pollutant pathways	Shifted temperatures/precipitation & weather patterns/extremes no longer matching infrastructure tolerance ranges	Threat 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 accelerated	Conflicts 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 America	Similar 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 unclear	Similar to AMOC but possibly smaller impact	Similar to AMOC but impact is not completely clear	Up to 2-3°C cooling in North Atlantic, global warming counteracted in Northern Europe / Eastern Canada	Large changes in ecosystems in affected regions (e.g. reduced North Atlantic productivity, regional ocean acidification, deoxygenation)	Impact unclear, but could be similar to AMOC	Similar to AMOC but smaller impact	Major disruptions of agriculture in Northern Europe and Sahel, impacting food security	Similar to AMOC but impact is not completely clear, potentially a large change in N. Atlantic ecosystems	Conflicts over food and water, displacement from uninhabitable areas, anomie, financial crises, etc	1.1-3.8°C GW, very fast (10 years), regional impacts
Monsoon shifts (intensification or collapse, e.g. South Asian, West African, South American)	No impact	Monsoon intensity & extremes projected to increase with warming, or strong drop due to aerosol-induced collapse	No Impact	Shifted precipitation may lead to water shortages	Drastic precipitation changes	Change in tropical and subtropical climates	Change in vegetation and ecosystems in general relying on the monsoon	Changes to where monsoons redistribute air pollution	More intense monsoons overwhelming current infrastructure; monsoon collapse leaving infrastructure mal-adapted	Changed vegetation, agriculture dependent on monsoon rainfall will impact livelihoods and food security	WAM could drive Sahel greening, SAM could affect Amazon	Conflicts 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 dieback	No impact	Increasing extreme weather events (e.g. wet bulb spikes, wildfires) in region	Additional global warming (0.1-0.2°C, depending on extent)	Decreased precipitation may lead to water shortages	Declining regional precipitation in Amazon and Southern Cone region	Over 1°C extra regional warming	Parts of rainforest (particularly in South & East) shift to degraded forest or savannah	Smoke from increased wildfires	Minor impact	Decreased precipitation would impact agricultural belt of Brazil and into Southern Cone	Amplified global warming, bringing other warming thresholds closer	Conflicts 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 expansion	No impact	Increasing extreme weather events (e.g. wildfires)	Complex effects – dieback releases carbon but reduces albedo, expansion vice versa	May change with evapotranspiration-induced weather pattern shifts	Changes to evapotranspiration likely to shift regional weather patterns	Regional changes due to changes in land albedo	Shift to open, steppe/prairie-like ecosystems in south, tundra afforestation in north	Smoke from wildfires	Minor impact	Disruption of traditional Indigenous food systems	Complex interplay with permafrost thaw, northern expansion adds to Arctic warming; drives lake browning	Anomie 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-off	Decreased coastal protection (coastal erosion)	Increased vulnerability to extreme weather events	Limited impact on GW until very long term	No impact	Minor impacts	Minor impact	Tropical and subtropical coral reefs mostly die-off, resulting in great biodiversity loss	No impact	Loss of coastal protection services may require engineered replacements	Impact on marine food web, Impact on 500 million livelihoods and food security	Possible interaction with nearby mangroves and seagrass die-off and marine regime shifts	Conflicts 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 events	Loss of C sink and release of GHGs, but small impact at global scale	Reduced coastal protection can allow greater seawater ingress, with storms and, aquifer salinisation	Minor impact	No impact	Many mangroves & seagrass ecosystems die-off, resulting in great biodiversity & ecosystem services loss	No impact	Loss of coastal protection services may require engineered replacements	Impact on marine food web, fishery and food security	Possible interaction with nearby coral reef die-off and marine regime shifts	Conflicts 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 impact	Greater vulnerability to drought or extremely high rainfall	Shifts in carbon storage – some GHG release possible (but globally small)	Greater groundwater depletion (with shrub encroach- ment)	Regional precipitation changes	Complex regional temperature change from changes to albedo and eco- hydrology	Change in vegetation, leading to biodiversity loss, reduced fires with shrub encroachment	No impact	Minor impact	Loss of grazing lands will impact livelihoods and food security	Possible interaction with nearby dryland and tropical forest tipping points	Conflicts over food and water, displacement from uninhabitable areas, anomie, etc	Regionally variable rainfall & fire thresholds, regional impacts
Temperate forestsdieback	No impact	Increased wildfires	Carbon emissions (amplifying global warming)	Less atmospheric water supply and groundwater recharge	Changes to evapotranspiration likely to shift regional weather patterns	Regional warming in summer due to less evaporative cooling and cloud cover	Change in forest ecosystems leading to biodiversity loss	Smoke from wildfires	Minor impact	Loss of indirect ecosystem services (e.g. pollinators, groundwater recharge)	Possible impacts on nearby boreal forest	Anomie because of loss of livelihoods and cultural loss	Thresholds unknown regional impacts
Drylands (ecosystem regime shift)	No impact	Greater vulnerability to drought or extremely high rainfall	Shifts 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 loss	No impact	Minor impact	Aridification/desertification or shrub encroachment will impact agriculture and food security	Possible interaction with nearby savannah and tropical forest tipping points	Conflict 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 impact	No impact	Increased GHG emissions (reduced for salinisation) could impact GW	Water quality decline could lead to water shortages	Minor impact	Minor impact	Lake ecosystem regime shift, biodiversity loss	Some algae blooms are toxic	Minor impacts	Freshwater fish stock decline could impact food security; water shortages could impact agriculture and food security	No impact	Conflict over water, anomie due to livelihood and cultural loss, etc	Variable 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 shift	Minor impact (loss of kelp forests could reduce coastal protection in some places)	No impact	Major changes in ocean productivity, carbon sinks & ocean biogeochemistry could have moderate impact on GW	No impact	Minor impact	Minor impact	Biodiversity loss from trophic cascades and regime shifts	Coastal eutrophication can lead to e.g. toxic ‘red tides’	Minor impact	Fish stock collapse could impact food security	Minor impact via reduced carbon sink amplifying GW	Conflicts 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