IPCC Special Report on Global Warming of 1.5ºC

Relevance:
Mains: GSIII-

• Environmental conservation
• Environmental pollution & degradation

• Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels.
• Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate.
• Even assuming full implementation of conditional and unconditional Nationally Determined Contributions(NDC's) submitted by nations in the Paris Agreement, net emissions would increase compared to 2010, leading to a warming of about 3 °C by 2100.
• Warming greater than the global annual average is being experienced in many land regions and seasons, including two to three times higher in the Arctic.
• Warming is generally higher over land than over the ocean.

Droughts and floods

• Risks from droughts and precipitation deficits, heavy precipitation associated with tropical cyclones are projected to be higher at 2°C compared to 1.5°C of global warming.
• As a consequence of heavy precipitation, the fraction of the global land area affected by flood hazards is projected to be larger at 2°C compared to 1.5°C of global warming.

Sea-level rise

• By 2100, the global mean sea level rise is projected to be around 0.1 meters lower with global warming of 1.5°C compared to 2°C.
• Sea level will continue to rise well beyond 2100, and the magnitude and rate of this rise depend on future emission pathways.
• Increasing warming amplifies the exposure of small islands, low-lying coastal areas, and deltas to the risks associated with sea-level rise for many human and ecological systems, including increased saltwater intrusion, flooding, and damage to infrastructure.
• A slower rate of sea-level rise enables greater opportunities for adaptation in the human and ecological systems of small islands, low-lying coastal areas, and deltas.
• A reduction of 0.1 m in global sea-level rise implies that up to 10 million fewer people would be exposed to related risks.

Impact on biodiversity and ecosystems

• On land, impacts on biodiversity and ecosystems, including species loss, extinction, forest fires, and the spread of invasive species are projected to be lower at 1.5°C of global warming compared to 2°C.
• High-latitude tundra and boreal forests are particularly at risk of climate change-induced degradation and loss, with woody shrubs already encroaching into the tundra and this will proceed with further warming.
• Limiting global warming to 1.5°C rather than 2°C is projected to prevent the thawing over centuries of a permafrost area in the range of 1.5 to 2.5 million km2.

Impact on ocean temperature and marine biodiversity

• Limiting global warming to 1.5°C compared to 2°C is projected to reduce increases in ocean temperature as well as associated increases in ocean acidity and decreases in ocean oxygen levels.
• There is a high probability of a sea ice-free Arctic Ocean during summer being substantially lower at global warming of 1.5°C when compared to 2°C. 
• Global warming of 1.5°C is projected to shift the ranges of many marine species to higher latitudes and reduce the productivity of fisheries and aquaculture (especially at low latitudes).
• Coral reefs are projected to decline by a further 70–90% at 1.5°C with larger losses (>99%) at 2°C.
• The level of ocean acidification due to increasing CO2 concentrations associated with global warming of 2°C impacts the growth, development, calcification, survival, and thus the abundance of a broad range of species, for example, from algae to fish.
• Impacts of climate change in the ocean are increasing risks to fisheries and aquaculture via impacts on the physiology, survivorship, habitat, reproduction, disease incidence, and risk of invasive species but are projected to be less at 1.5°C of global warming than at 2°C.

Deepening of Poverty

• Populations at disproportionately higher risk of adverse consequences with global warming of 1.5°C and beyond include disadvantaged and vulnerable populations, some indigenous peoples, and local communities dependent on agricultural or coastal livelihoods.
• Regions at disproportionately higher risk include Arctic ecosystems, dryland regions, small island developing states, and Least Developed Countries.
• Limiting global warming to 1.5°C, compared with 2°C, could reduce the number of people both exposed to climate-related risks and susceptible to poverty by up to several 100 million by 2050.

Impact on human health

• Lower risks are projected at 1.5°C than at 2°C for heat-related morbidity and mortality.
• Urban heat islands often amplify the impacts of heatwaves in cities.
• Risks from some vector-borne diseases, such as malaria and dengue fever, are projected to increase with warming from 1.5°C to 2°C.

Food security

• Reductions in projected food availability are larger at 2°C than at 1.5°C of global warming in the Sahel, southern Africa, the Mediterranean, central Europe, and the Amazon.
• Livestock is projected to be adversely affected by rising temperatures, depending on the extent of changes in feed quality, the spread of diseases, and water resource availability.

• Limiting warming below or close to 1.5 °C would require decreasing net emissions by around 45% by 2030 and reach net zero by 2050 (i.e. keeping total cumulative emissions within a carbon budget).
• Pathways (i.e. scenarios and portfolios of mitigation options) that would allow such reduction by 2050 describe a rapid transition towards producing electricity through lower-emission methods, and increasing use of electricity instead of other fuels in sectors such as transportation.
• It also requires switching to renewable energy, lower energy use, and enhancing energy efficiency.
• Most pathways describe a larger role for nuclear energy and carbon capture and storage and less usage of natural gas.
• CO2 emissions from industry can be reduced through combinations of new and existing technologies and practices, including electrification, hydrogen, sustainable bio-based feedstocks, product substitution, and carbon capture, utilization, and storage (CCUS). 
• The urban and infrastructure system transition consistent with limiting global warming to 1.5°C requires changes in land and urban planning practices, as well as deeper emissions reductions in transport and buildings.
• The systems transitions consistent with adapting to and limiting global warming to 1.5°C include the widespread adoption of new and possibly disruptive technologies and practices and enhanced climate-driven innovation.
• Carbon dioxide removal (CDR) technologies like bioenergy with carbon capture and storage (BECCS) can be used to compensate for residual emissions and, achieve net negative emissions to return global warming to 1.5°C following a peak.
• However, CDR technology is in its infancy and the feasibility is an open question.
• Similarly, solar radiation management (SRM) has the potential to limit warming, but face large uncertainties and knowledge gaps as well as substantial risks, and constraints.
• Education, information, and community approaches, including those that are informed by indigenous knowledge, can accelerate the wide-scale behaviour changes consistent with adapting to and limiting global warming to 1.5°C. 
• International cooperation is a critical enabler for developing countries to strengthen their action for the implementation of 1.5°C-consistent climate responses, including through enhancing access to finance and technology and enhancing domestic capacities.

• Climate change impacts and responses are closely linked to sustainable development which balances social well-being, economic prosperity, and environmental protection.
• The consideration of ethics and equity can help address the uneven distribution of adverse impacts associated with 1.5°C.
• Meeting a 1.5 °C target is possible but would require deep emissions reductions and rapid, far-reaching, and unprecedented changes in all aspects of society.