Rising sea levels threaten New York and other major cites, the world's glaciers are melting at alarming rates and global fisheries are shrinking. These are just some of the impacts that emissions of greenhouse gases have already triggered across the planet, according to a new landmark report from the United Nations' Intergovernmental Panel on Climate Change (IPCC).
More than 100 authors from 36 countries assessed the latest scientific literature related to the ocean and cryosphere in a changing climate for the report, referencing about 7,000 scientific publications for the report titled -- "Special Report on the Ocean and Cryosphere in a Changing Climate." It is the last of three special reports from the IPCC following on climate change.
“The open sea, the Arctic, the Antarctic and the high mountains may seem far away to many people,” said Hoesung Lee, Chair of the IPCC. “But we depend on them and are influenced by them directly and indirectly in many ways – for weather and climate, for food and water, for energy, trade, transport, recreation and tourism, for health and wellbeing, for culture and identity.”
“If we reduce emissions sharply, consequences for people and their livelihoods will still be challenging, but potentially more manageable for those who are most vulnerable,” Lee said. “We increase our ability to build resilience and there will be more benefits for sustainable development.”
Warming and changes in ocean chemistry are already disrupting species throughout the ocean food web, with impacts on marine ecosystems and people that depend on them, the report said.
To date, the ocean has taken up more than 90 percent of the excess heat in the climate system. By 2100, the ocean will take up 2 to 4 times more heat than between 1970 and the present if global warming is limited to 2 degree Celsius, and up to 5 to 7 times more at higher emissions. Ocean warming reduces mixing between water layers and, as a consequence, the supply of oxygen and nutrients for marine life.
Marine heatwaves have doubled in frequency since 1982 and are increasing in intensity. They are projected to further increase in frequency, duration, extent and intensity. Their frequency will be 20 times higher at 2 degree Celsius warming, compared to pre-industrial levels. They would occur 50 times more often if emissions continue to increase strongly.
The ocean has taken up between 20 to 30 percent of human-induced carbon dioxide emissions since the 1980s, causing ocean acidification. Continued carbon uptake by the ocean by 2100 will exacerbate ocean acidification.
Ocean warming and acidification, loss of oxygen and changes in nutrient supplies, are already affecting the distribution and abundance of marine life in coastal areas, in the open ocean and at the sea floor.
Shifts in the distribution of fish populations have reduced the global catch potential. In the future, some regions, notably tropical oceans, will see further decreases, but there will be increases in others, such as the Arctic. Communities that depend highly on seafood may face risks to nutritional health and food security.
The MSC responds
In response to release of the report, eco-label NGO the Marine Stewardship Council (MSC) said the fishing industry and governments need to urgently step up cooperation to ensure the health and productivity of our oceans in the context of climate change.
The group cited recent declines in North Sea cod stocks as an example of the results of climate change.
"The IPCC report demonstrates that progress towards sustainable fisheries management is now more urgent than ever before," said the MSC's Hans Nieuwenhuis.
"Sustainable, well-managed fisheries which have effective monitoring, regulation and management systems in place are more resilient and able to adapt to climate change. Yet globally governments and fisheries managers are already struggling to reach consensus on how to manage ocean resources in a way which reflects the new reality of changing climates."
The NGO said that its suspension earlier this year of MSC certification of North East Atlantic mackerel demonstrates the challenge in reaching international consensus on managing fishing stocks that are moving across geopolitical boundaries.
Following the rapid change in the distribution of mackerel since 2007, coastal states have been unable to agree catch quotas in line with scientific advice. To resolve this issue, the mackerel fisheries have committed to delivering an effective harvest strategy and well-defined harvest control rules by mid-2020. The MSC is working with partners to support these efforts and encourage a resolution to the dispute.