Notes from the UN Intergovernmental Panel on Climate Change (IPCC) Climate Change 2023 Synthesis Report (AR6)

The recent Synthesis Report prepared from the United Nations’ Intergovernmental Panel on Climate Change (IPCC) Assessment Report 6 (AR6) discusses current risks and future risks, by continuing to live our current lifestyle. This section consists of various statements excerpted from this 2023 report:

“The cumulative scientific evidence is unequivocal: climate change is a threat to human well-being and planetary health (very high confidence). Any further delay in concerted anticipatory global action on adaptation and mitigation will miss a brief and rapidly closing window of opportunity to secure a liveable and sustainable future for all (very high confidence).” P. 89.

Current Risks at 1.5°C Global Warming (IPCC AR6 SYR Report)

“Principal hazards and associated risks expected in the near term (at 1.5°C global warming) are:

Increased intensity and frequency of hot extremes and dangerous heat-humidity conditions, with increased human mortality, morbidity, and labour productivity loss (high confidence).
Increasing frequency of marine heatwaves will increase risks of biodiversity loss in the oceans, including from mass mortality events (high confidence).
Near-term risks for biodiversity loss are moderate to high in forest ecosystems (medium confidence) and kelp and seagrass ecosystems (high to very high confidence) and are high to very high in Arctic sea-ice and terrestrial ecosystems (high confidence) and warm-water coral reefs (very high confidence).
More intense and frequent extreme rainfall and associated flooding in many regions including coastal and other low-lying cities (medium to high confidence), and increased proportion of and peak wind speeds of intense tropical cyclones (high confidence).
High risks from dryland water scarcity, wildfire damage, and permafrost degradation (medium confidence).
Continued sea level rise and increased frequency and magnitude of extreme sea level events encroaching on coastal human settlements and damaging coastal infrastructure (high confidence), committing low-lying coastal ecosystems to submergence and loss (medium confidence), expanding land salinization (very high confidence), with cascading to risks to livelihoods, health, well-being, cultural values, food and water security (high confidence).
Climate change will significantly increase ill health and premature deaths from the near to long term (high confidence). Further warming will increase climate-sensitive food-borne, water-borne, and vector-borne disease risks (high confidence), and mental health challenges including anxiety and stress (very high confidence).”
Cryosphere-related changes in floods, landslides, and water availability have the potential to lead to severe consequences for people, infrastructure and the economy in most mountain regions (high confidence).
The projected increase in frequency and intensity of heavy precipitation (high confidence) will increase rain-generated local flooding (medium confidence).” P. 98-99.

“Multiple climate change risks will increasingly compound and cascade in the near term (high confidence). Many regions are projected to experience an increase in the probability of compound events with higher global warming (high confidence) including concurrent heatwaves and drought. Risks to health and food production will be made more severe from the interaction of sudden food production losses from heat and drought, exacerbated by heat-induced labour productivity losses (high confidence) (Figure 4.3). These interacting impacts will increase food prices, reduce household incomes, and lead to health risks of malnutrition and climate-related mortality with no or low levels of adaptation, especially in tropical regions (high confidence). Concurrent and cascading risks from climate change to food systems, human settlements, infrastructure and health will make these risks more severe and more difficult to manage, including when interacting with non-climatic risk drivers such as competition for land between urban expansion and food production, and pandemics (high confidence). Loss of ecosystems and their services has cascading and long-term impacts on people globally, especially for Indigenous Peoples and local communities who are directly dependent on ecosystems, to meet basic needs (high confidence). Increasing transboundary risks are projected across the food, energy and water sectors as impacts from weather and climate extremes propagate through supply-chains, markets, and natural resource flows (high confidence) and may interact with impacts from other crises such as pandemics. Risks also arise from some responses intended to reduce the risks of climate change, including risks from maladaptation and adverse side effects of some emissions reduction and carbon dioxide removal measures, such as afforestation of naturally unforested land or poorly implemented bioenergy compounding climate-related risks to biodiversity, food and water security, and livelihoods (high confidence). P. 99.

Warnings for Further Increases in Temperature (IPCC AR6 SYR Report)

“Global mean sea level rise will continue in the 21st century (virtually certain), with projected regional relative sea level rise within 20% of the global mean along two-thirds of the global coastline (medium confidence). … At sustained warming levels between 2°C and 3°C, the Greenland and West Antarctic ice sheets will be lost almost completely and irreversibly over multiple millennia (limited evidence). The probability and rate of ice mass loss increase with higher global surface temperatures (high confidence). Over the next 2000 years, global mean sea level will rise by about 2 to 3 m if warming is limited to 1.5°C and 2 to 6 m if limited to 2°C (low confidence).” P. 77 AR6.

“With increasing warming, adaptation options will become more constrained and less effective.” P. 78.

“With every increment of warming, climate change impacts and risks will become increasingly complex and more difficult to manage.” P. 72, AR6

“With increasing global warming, more limits to adaptation will be reached and losses and damages, strongly concentrated among the poorest vulnerable populations, will increase (high confidence).” P. 78.

“Exceeding a specific remaining carbon budget results in higher global warming. Achieving and sustaining net negative global CO2 emissions could reverse the resulting temperature exceedance (high confidence). Continued reductions in emissions of short-lived climate forcers, particularly methane, after peak temperature has been reached, would also further reduce warming (high confidence). Only a small number of the most ambitious global modelled pathways limit global warming to 1.5°C (>50%) without overshoot.”

“Overshoot increases the risks of severe impacts, such as increased wildfires, mass mortality of trees, drying of peatlands, thawing of permafrost and weakening natural land carbon sinks; such impacts could increase releases of GHGs making temperature reversal more challenging (medium confidence).” P. 87

How to Prevent Increases Above 2°C (IPCC AR6 SYR Report)

“All global modelled pathways that limit warming to 2°C (>67%) or lower by 2100 involve rapid and deep and in most cases immediate GHG emissions reductions in all sectors (see also 4.1, 4.5). Reductions in GHG emissions in industry, transport, buildings, and urban areas can be achieved through a combination of energy efficiency and conservation and a transition to low-GHG technologies and energy carriers (see also 4.5, Figure 4.4). Socio-cultural options and behavioural change can reduce global GHG emissions of end-use sectors, with most of the potential in developed countries, if combined with improved infrastructure design and access. (high confidence) P. 86.

“All global modelled pathways that limit warming to 2°C (>67%) or lower by 2100 involve GHG emission reductions in all sectors (high confidence). The contributions of different sectors vary across modelled mitigation pathways. In most global modelled mitigation pathways, emissions from land-use, land-use change and forestry, via reforestation and reduced deforestation, and from the energy supply sector reach net zero CO2 emissions earlier than the buildings, industry and transport sectors (Figure 4.1). Strategies can rely on combinations of different options (Figure 4.1, Section 4.5), but doing less in one sector needs to be compensated by further reductions in other sectors if warming is to be limited. (high confidence).” P. 93

Statements Indicating How Agriculture is Important

“AFOLU (Agriculture, Forestry, and Other Land Use) mitigation options, when sustainably implemented, can deliver large-scale GHG emission reductions and enhanced CO2 removal; however, barriers to implementation and trade-offs may result from the impacts of climate change, competing demands on land, conflicts with food security and livelihoods, the complexity of land ownership and management systems, and cultural aspects (see 3.4.1). All assessed modelled pathways that limit warming to 2°C (>67%) or lower by 2100 include land-based mitigation and land-use change, with most including different combinations of reforestation, afforestation, reduced deforestation, and bioenergy. However, accumulated carbon in vegetation and soils is at risk from future loss (or sink reversal) triggered by climate change and disturbances such as flood, drought, fire, or pest outbreaks, or future poor management. (high confidence)” p 87.

“For agriculture, land, and food systems, many land management options and demand-side response options (e.g., dietary choices, reduced post-harvest losses, reduced food waste) can contribute to eradicating poverty and eliminating hunger while promoting good health and well-being, clean water and sanitation, and life on land (medium confidence). In contrast, certain adaptation options that promote intensification of production, such as irrigation, may have negative effects on sustainability (e.g., for biodiversity, ecosystem services, groundwater depletion, and water quality) (high confidence).” P. 88.

“All global modelled pathways that limit warming to 2°C (>67%) or lower by 2100 involve reductions in both net CO2 emissions and non-CO2 emissions (see Figure 3.6) (high confidence). For example, in pathways that limit warming to 1.5°C (>50%) with no or limited overshoot, global CH4 (methane) emissions are reduced by 34 [21 to 57]% below 2019 levels by 2030 and by 44 [31 to 63]% in 2040 (high confidence). Global CH4 emissions are reduced by 24 [9 to 53]% below 2019 levels by 2030 and by 37 [20 to 60]% in 2040 in modeled pathways that limit warming to 2°C with action starting in 2020 (>67%) (high confidence).” P. 93

“Climate resilient development strategies that treat climate, ecosystems and biodiversity, and human society as parts of an integrated system are the most effective (high confidence).” P. 114.

Reference

IPCC, 2023: Sections. In: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, pp. 35-115, doi: 10.59327/IPCC/AR6-9789291691647