On September 24, 2019, the Intergovernmental Panel on Climate Change released a report that concentrates on the oceans and ice (the cryosphere). The Summary alone is 45 pages and the full report is available here. Both have extensive charts and graphs.
This diary provides a summary of the summary. When they talk about “ecosystem services” they mean things that the ecosystem does for us, like providing food and oxygen. Emphasis added by me in places.
SECTION A — Observed changes and impacts
- Observed physical changes
- Over the last decades, global warming has led to widespread shrinking of the cryosphere, with mass loss from ice sheets and glaciers, reductions in snow cover and Arctic sea ice extent and thickness, and increased permafrost temperature.
- It is virtually certain that the global ocean has warmed unabated since 1970 and the ocean has taken up more than 90% of the excess heat in the climate system.
- The rate of warming has more than doubled since 1993.
- Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity.
- By absorbing more CO2 , the ocean has become more acidic near the surface, and lost oxygen down to 1000 meters.
- Global mean sea level is rising, with acceleration in recent decades, due to:
- Ice loss from the Greenland and Antarctic ice sheets,
- Ice loss from glaciers
- Ocean thermal expansion
- Increases in tropical cyclone winds and rainfall, and increases in extreme waves, combined with relative sea level rise, exacerbate extreme sea level events and coastal hazards.
- Observed impacts on ecosystems
- Changes in ice and water have impacted land and freshwater species in high mountain areas have contributed to changing the seasonal activities, abundance and distribution of ecologically, culturally, and economically important plant and animal species, ecological disturbances, and ecosystem functioning.
- Since 1950 many marine species have shifted their geographical range and
seasonal activities in response to ocean warming, sea ice change and biogeochemical changes, such as oxygen loss.
- This has resulted in shifts in species composition, abundance and biomass production of ecosystems worldwide. Altered interactions between species have caused cascading impacts on ecosystem structure and functioning. In some marine ecosystems species are impacted by both the effects of fishing and climate changes.
- Coastal ecosystems are affected by ocean warming, including intensified marine heatwaves, acidification, loss of oxygen, salinity intrusion and sea level rise. Impacts are already observed on habitat area and biodiversity, as well as ecosystem functioning and services.
- Less ice in the Arctic and on mountains has had negative impacts since the middle of the 20th century. Costs and benefits have been unequally distributed across populations and regions. Adaptation efforts have benefited from the inclusion of Indigenous knowledge and local knowledge. Affected were:
- food security
- water resources
- water quality
- livelihoods
- health and well-being
- infrastructure
- transportation
- tourism and recreation
- culture of human societies, particularly for Indigenous peoples dependant on fisheries
- Coastal communities are exposed to multiple climate-related hazards, including tropical cyclones, extreme sea levels, marine heatwaves, sea ice loss, and permafrost thaw.
- A diversity of responses has been implemented worldwide, mostly after extreme events, but also some in anticipation of future sea level rise, e.g., in the case of large infrastructure.
Section B — Projected changes and risks
- Physical changes
- 1. Global-scale glacier mass loss, permafrost thaw, and decline in snow cover and Arctic sea ice extent are projected to continue in the near-term (2031–2050) due to surface air temperature increases, with unavoidable consequences for river runoff and local hazards. The Greenland and Antarctic Ice Sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond.
- The rates and magnitudes of these cryospheric changes are projected to increase further in the second half of the 21st century in a high greenhouse gas emissions scenario. Strong reductions in greenhouse gas emissions in the coming decades are
projected to reduce further changes after 2050.
- Risks to ecosystems
- Future land cryosphere changes will continue to alter terrestrial and freshwater ecosystems in high-mountain and polar regions with major shifts in species distributions resulting in changes in ecosystem structure and functioning, and eventual loss of globally unique biodiversity. Wildfire is projected to increase significantly for the rest of this century across most tundra and boreal regions, and also in some mountain regions.
- Risks to people and ecosystem services
- Future cryosphere changes on land are projected to affect water resources and their uses, such as hydropower and irrigated agriculture in and downstream of high-mountain areas, as well as livelihoods in the Arctic. Changes in floods, avalanches, landslides, and ground destabilization are projected to increase risk for infrastructure, cultural, tourism, and recreational assets.
- Shifts in fish distribution and decreases in their abundance are projected to affect income, livelihoods, and food security of marine resource-dependent communities.
- Long-term loss and degradation of marine ecosystems compromises the ocean’s role in cultural, recreational, and intrinsic values important for human identity and well-being.
- Rising sea level plus warming and acidification are projected to exacerbate risks
for human communities in low-lying coastal areas. In Arctic human communities without rapid land uplift, and in urban atoll islands, risks are projected to be moderate to high even under a low emissions scenario, including reaching adaptation limits.
- Under a high emissions scenario, delta regions and resource rich coastal cities are projected to experience moderate to high risk levels after 2050 under current adaptation. Ambitious adaptation including transformative governance is expected to reduce risk.
[One has to wonder what “transformative governance” might be...]
Section C — Implementing responses
- Challenges
- Impacts of changes increasingly challenge current governance efforts to develop and implement adaptation responses, and in some cases pushing them to their limits. People with the highest exposure and vulnerability are often those with lowest capacity to respond.
- The services provided by ocean and cryosphere-related ecosystems can be supported by protection, restoration, precautionary management of renewable resource use, and the reduction of pollution and other stressors. Integrated water management and adaptation approaches lower climate risks locally and provide multiple societal benefits. However, ecological, financial, institutional and governance constraints for such actions exist.
- in many regions, adaptation will only be effective under the lowest levels of warming.
- Coastal communities face challenges in crafting local and integrated responses to sea level rise that balance costs, benefits and trade-offs of available options and that can be adjusted over time.
- Enabling conditions
- Urgent and ambitous emissions reductions along with coordinated adaptation are necessary for climate resilience and sustainable development.
- Education and climate literacy, monitoring and forecasting, use of all available knowledge sources, sharing of data, information and knowledge, finance, addressing social vulnerability and equity, and institutional support are also essential.