Nereus director (science) William Cheung (UBC) and Thomas Frölicher (University of Bern) are co-authors on the newly released Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), which was approved at the 51^st session of the Intergovernmental Panel on Climate Change (IPCC) and presented on September 25, 2019. The Summary for Policymakers (SPM) is comprised of three major sections – ‘Observed changes and impacts’, ‘Projected changes and risk’, and ‘Implementing Responses to Ocean and Cryosphere Change’. Findings within the report are assessed according to evidence and agreement, from very low to very high confidence, and likelihood (e.g., from exceptionally unlikely to virtually certain). Some (of the many) key findings within the report are the following:

Observed Physical Changes

• Ice sheets and glaciers have lost mass (very high confidence), largely in the Greenland Ice Sheet and Antarctic Ice Sheet, leading to accelerated sea-level rise
• Arctic sea ice has very likely decreased during all months from 1978-2018, with continued September sea ice reductions very likely in each of the coming decades
• “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 (high confidence)”
• Marine heatwaves have increased globally, become more intense, extensive and longer lasting
• The ocean continues to acidify, due to it absorbing “20-30% (very likely) of total anthropogenic CO₂ emissions since the 1980s”
• Marine species are increasingly shifting their distribution toward the poles

Projected Physical Changes

• “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 (high confidence), with unavoidable consequences for river runoff and local hazards (high confidence)”
• In all emission scenarios, average annual and summer runoff from glaciers are projected to peak at or before the end of the 21^st century
• It is virtually certain the ocean will continue to warm throughout the 21^st century
• It is virtually certain the ocean will continue to acidify due to carbon sequestration

Projected Physical Changes (Continued)

• “Marine heatwaves are projected to further increase in frequency, duration, spatial extent and intensity (maximum temperature) (very high confidence)”
• El Niño and La Niña events will likely increase in frequency this century
• Global marine biomass will decrease, impacting fisheries catch potential and productivity, with species composition continuing to shift at all ocean depths
• Coastal ecosystems (e.g. seagrass meadows, saltmarshes, mangroves, coral reefs, etc.) are all at risk of increasing losses
• Human communities in low-lying coastal areas are especially at risk due to sea-level rise, ocean warming and acidification, and arctic sea ice loss, with the potential for some small island nations to become uninhabitable

Implementing Responses to Ocean and Cryosphere Change

• “People with the highest exposure and vulnerability are often those with lowest capacity to respond (high confidence)”
• Governance arrangements are fragmented, making it more difficult to respond to the increasing risks due to climate change
• There are financial, technological and institutional barriers to implementing responses to climate change, which impede “resilience building and risk reduction measures”
• Ecosystem management tools are “most successful when they are community-supported, are science-based whilst also using local knowledge and Indigenous knowledge, have long-term support that includes the reduction or removal of non-climatic stressors, and under the lowest levels of warming (high confidence)”

Towards the conclusion, the authors stress that “enabling climate resilience and sustainable development depends critically on urgent and ambitious emissions reductions coupled with coordinated sustained and increasingly ambitious adaptation actions (very high confidence)” and that there is a need for “cooperation and coordination among governing authorities across spatial scales and planning horizons.” They add that it’s essential to improve climate change education, literacy and “use of all available knowledge sources, sharing of data, information and knowledge, finance, addressing social vulnerability and equity and institutional support”.