IPCC report warns of ocean warming and dire impacts
A separate IPCC report examines how oceans are affected by climate change, pointing, among others, to increased warming, sea level rise and the risks confronting coastal communities.
THE Intergovernmental Panel on Climate Change’s Special Report on the Ocean and Cryosphere in a Changing Climate, which was adopted by member states on 24 September in Monaco, has issued dire warnings on the warming of the oceans and the widespread shrinking of the cryosphere.
(The report defines the cryosphere as ‘the components of the Earth System at and below the land and ocean surface that are frozen, including snow cover, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground’.)
Member states of the IPCC adopted the report’s Summary for Policymakers (SPM) and the underlying assessment report at the 51st session of the IPCC in Monaco.
The adoption was 18 hours behind schedule, as the meeting, which began on 20 September, was initially scheduled to end on 23 September. Instead, it spilled over to the next day, following five days of intense negotiations over the key messages to be presented in the report. The SPM was negotiated line-by-line among governments and authors of the report and saw some contentious issues being raised.
The SPM comprises three sections: (i) ‘Observed changes and impacts’; (ii) ‘Projected changes and risks’; and (iii) ‘Implementing responses to ocean and cryosphere change’.
On observed changes and impacts, the SPM states that ‘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 has taken up more than 90% of the excess heat in the climate system. Since 1993, the rate of ocean warming has more than doubled. Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity. By absorbing more CO2 [carbon dioxide], the ocean has undergone increasing surface acidification. A loss of oxygen has occurred from the surface to 1000 m.’
‘Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets, as well as continued glacier mass loss and 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,’ warns the SPM.
It also states: ‘Coastal ecosystems are affected by ocean warming, including intensified marine heatwaves, acidification, loss of oxygen, salinity intrusion and sea level rise, in combination with adverse effects from human activities on ocean and land. Impacts are already observed on habitat area and biodiversity, as well as ecosystem functioning and services.’
‘Since the mid-20th century, the shrinking cryosphere in the Arctic and high-mountain areas has led to predominantly negative impacts on food security, water resources, water quality, livelihoods, health and well-being, infrastructure, transportation, tourism and recreation, as well as culture of human societies, particularly for Indigenous peoples. Costs and benefits have been unequally distributed across populations and regions. Adaptation efforts have benefited from the inclusion of Indigenous knowledge and local knowledge,’ states the SPM further.
‘Coastal communities are exposed to multiple climate-related hazards, including tropical cyclones, extreme sea levels and flooding, marine heatwaves, sea ice loss, and permafrost thaw.’
It also adds though that ‘the attribution of current coastal impacts on people to sea-level rise remains difficult in most locations since impacts were exacerbated by human-induced non-climatic drivers, such as land subsidence (e.g., groundwater extraction), pollution, habitat degradation, reef and sand mining’.
Under the section on ‘Projected changes and risks’, the SPM highlights that ‘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’.
The SPM also warns that ‘Over the 21st century, the ocean is projected to transition to unprecedented conditions with increased temperatures, greater upper ocean stratification, further acidification, oxygen decline, and altered net primary production. Marine heatwaves and extreme El Niño and La Niña events are projected to become more frequent.’
According to the SPM, sea level will continue to rise at an increasing rate. ‘Extreme sea level events that are historically rare (once per century in the recent past) are projected to occur frequently (at least once per year) at many locations by 2050 in all RCP, especially in tropical regions.’ (RCPs or ‘representative concentration pathways’ are scenarios which describe alternative trajectories for greenhouse gas emissions and the resulting atmospheric concentration from 2001 to 2100.)
‘A decrease in global biomass of marine animal communities, their production, and fisheries catch potential, and a shift in species composition are projected over the 21st century in ocean ecosystems from the surface to the deep seafloor under all emission scenarios. The rate and magnitude of decline are projected to be highest in the tropics…,’ cautions the SPM further.
Under the section on ‘Implementing responses to ocean and cryosphere change’, the SPM highlights that the ‘Impacts of climate-related changes in the ocean and cryosphere increasingly challenge current governance efforts to develop and implement adaptation responses from local to global scales, 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 SPM also states: ‘The far-reaching services and options provided by ocean and cryosphere-related ecosystems can be supported by protection, restoration, precautionary ecosystem-based management of renewable resource use, and the reduction of pollution and other stressors. Integrated water management and ecosystem-based adaptation approaches lower climate risks locally and provide multiple societal benefits. However, ecological, financial, institutional and governance constraints for such actions exist, and in many contexts ecosystem-based adaptation will only be effective under the lowest levels of warming.’
‘Coastal communities face challenging choices in crafting context-specific and integrated responses to sea level rise that balance costs, benefits and trade-offs of available options and that can be adjusted over time. All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and retreat, wherever possible, can play important roles in such integrated responses.’
The SPM also highlights that ‘Enabling climate resilience and sustainable development depends critically on urgent and ambitious emissions reductions coupled with coordinated sustained and increasingly ambitious adaptation actions. Key enablers for implementing effective responses to climate-related changes in the ocean and cryosphere include intensifying cooperation and coordination among governing authorities across spatial scales and planning horizons. 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.’
Areas of contention
The SPM was adopted only after some difficult, line-by-line negotiations. A number of contentious issues had to be addressed through contact groups and huddles.
Among the areas of contention were the establishment of a link between the ocean report and the IPCC’s special report on 1.5°C warming (SR1.5), scenarios assessed in the ocean report, description of ‘high mountain regions’, the lack of adequate mention of small island developing states (SIDS) in the SPM, and discussion around the term ‘governance’.
In relation to a reference to SR1.5, a proposed sentence in the draft SPM read: ‘This assessment reinforces findings in IPCC SR1.5 and SRCCL (Special Report on Climate Change and Land), and IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) (very high confidence).’
Saudi Arabia and the Russian Federation were opposed to the sentence. Saudi Arabia said that it had no problem with the 1.5°C limit, but was against references to SR1.5 in the ocean report since SR1.5 had several limitations which were highlighted in the SR1.5 report. A long discussion ensued and the following compromise was arrived at: ‘This report reflects the state of science for ocean and cryosphere for low levels of global warming (1.5°C), as also assessed in earlier IPCC and IPBES reports.’ Saudi Arabia was also opposed to referencing SR1.5 in other sections of the SPM and compromises were found after intense negotiations.
The RCP scenarios assessed in the report were also questioned by several governments including Saudi Arabia and Ecuador. The primary concern related to using findings from two extreme scenarios (RCP2.6 and RCP8.5) and ignoring other scenarios (RCP4.5).
A footnote was added to clarify why only two scenarios were primarily used: ‘This report primarily uses RCP2.6 and RCP8.5 for the following reasons: These scenarios largely represent the assessed range for the topics covered in this report; they largely represent what is covered in the assessed literature…; and they allow a consistent narrative about projected changes. RCP4.5 and RCP6.0 are not available for all topics addressed in the report.’
Several developing countries such as India and Bhutan were of the view that the report focused too much on the Arctic and the description of ‘high mountain regions’ was not adequate. The solution arrived at was on the need to expand high mountain regions when underlying literature supported it, and a footnote was revised to this effect. The addition in the footnote said: ‘For a list of high mountain regions covered in this report, see Chapter 2.’
Sentences dealing with high mountain regions were either expanded or elaborated on, such as the following:
• ‘Glacier retreat and snow cover changes have contributed to localised declines in agricultural yields in some high mountain regions, including Hindu Kush Himalaya and the tropical Andes.’
• ‘High mountain aesthetic and cultural aspects have been negatively impacted by glacier and snow cover decline (e.g. in the Himalaya, East Africa, the tropical Andes).’
Another issue that gained prominence in the negotiations was inadequate mention of SIDS in the SPM. Following the discussions, SIDS were included in the following sentences:
• ‘Human communities in close connection with coastal environments, small islands (including Small Island Developing States, SIDS), polar areas and high mountains are particularly exposed to ocean and cryosphere change, such as sea level rise, extreme sea level and shrinking cryosphere.’
• ‘The low-lying coastal zone is currently home to around 680 million people (nearly 10% of the 2010 global population), projected to reach more than one billion by 2050. SIDS are home to 65 million people.’
• ‘Many low-lying megacities and small islands (including SIDS) are projected to experience historical centennial events at least annually by 2050 under RCP2.6, RCP4.5 and RCP8.5.’
SIDS and countries affected by tropical cyclones also wanted exclusive reference to tropical cyclones, and the SPM was adjusted accordingly. For example, the following sentences were added:
• ‘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.’
• ‘Anthropogenic climate change has increased observed precipitation, winds, and extreme sea level events associated with some tropical cyclones, which has increased intensity of multiple extreme events and associated cascading impacts. Anthropogenic climate change may have contributed to a poleward migration of maximum tropical cyclone intensity in the western North Pacific in recent decades related to anthropogenically-forced tropical expansion. There is emerging evidence for an increase in annual global proportion of Category 4 or 5 tropical cyclones in recent decades.’
*Third World Resurgence No. 341/342, 2019, pp 39-41