IPCC Report: Oceans and Ice Systems Already Facing Unprecedented Climate Impacts

IPCC Oceans Cryosphere Report

MONTE CARLO, Monaco – Today, the UN Intergovernmental Panel on Climate Change released the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) in the Principality of Monaco. This report, the product of a week of editing in which the scientists who authored the report took questions from delegations of 111 member nations, is the third Special Report in the IPCC’s Sixth Assessment Report Cycle, following the 1.5° Report in October 2018 and Lands report in August 2019.

The Special Report on Oceans and the Cryosphere offers a grim picture. We have simply waited too long to reduce emissions, and will be forced to grapple with impacts that can no longer be avoided. However, the difference between sharply reducing emissions and continuing along the “business as usual” pathway is stark: Under a low-emissions scenario, managing the impacts of climate change will be expensive but possible; doing nothing will result in unmanageably catastrophic effects.

Key Takeaways:

  • Oceans have gotten warmer, more acidic, and are losing oxygenresulting in a cascade of negative effects that wreak havoc on marine ecosystems, threaten the collapse of the world’s fisheries, and turbocharge deadly hurricanes and tropical storms.
  • Polar ice sheet loss has increased dramatically, overtaking thermal expansion and glacial melt as the predominant cause of sea level rise since the IPCC last made an assessment in 2013. Sea level rise is now accelerating and the IPCC is now forecasting higher sea levels under the high-emissions pathway. Even under a low-emissions scenario, most of the East and West Coasts of the U.S. will experience a hundred-year flood every year unless major investments are made to adapt to these coming extreme events. Globally, this investment would run up to hundreds of billions of dollars per year.
  • The world has reached or is nearing critical tipping points. Polar ice sheets may now be unstable, and as a result long-term melting may now be irreversible. Meanwhile, methane and carbon released as permafrost thaws will further contribute to warming, pushing toward a tipping point that, if passed, could trap the planet in a vicious feedback loop that could unleash accelerating warming.
  • Water scarcity and wildfires will become worse as glaciers melt and snowpack declines. Already, communities that rely on glacial melt and snow runoff for agriculture and drinking water are left high and dry, while wildfires have grown increasingly common in the Arctic and high mountains as snowpacks melt.


Current Impacts

Carbon emissions are driving unprecedented changes from the highest mountain peaks to the bottom of the ocean. The impacts are already significant and getting worse.


  • The world’s oceans have historically served as a buffer, taking up over 90% of the excess heat in the climate system since 1970 and up to a third of human-caused CO2 emissions since the 1980s.
  • Carbon emissions have led to an ocean that is warmer, more acidic and losing oxygen. This is having a cascade of negative effects, such as changing the presence and abundance of many species. Fisheries have been disrupted and fish catch has already been reduced in some regions.
  • Warming oceans are now fueling tropical and extratropical storms, loading them with additional rainfall and increasing their intensity. And sea level rise is elevating storm surge, contributing to extreme flooding events. 
  • Marine heat waves have doubled in frequency and have become longer-lasting, more intense, and more extensive events that have already resulted in large coral bleaching events and worldwide reef degradation. Nine out of ten marine heat waves are now attributable to climate change. 

Coastal impacts

  • Melting polar ice sheets have now begun to dominate sea level rise, and as a result, sea level rise is accelerating, eroding our coastlines, and increasing both high tides and storm tides, contributing to coastal flooding. Mass loss from the Greenland and Antarctic ice sheets has accelerated, and scientists cannot rule out the possibility that irreversible ice sheet instability has begun.
  • Coastal ecosystems, which help protect coastlines and buffer sea level rise and ocean acidification, are being degraded by climate change and other human disturbance.

High Mountains and Polar

Projected Impacts

Regardless of the future efforts to reduce carbon pollution, severe changes are now locked-in and managing those changes will require urgent and ambitious adaptation measures.

Coastal impacts 

Arctic impacts

High mountain impacts

On a business as usual path…

  • Ocean ecosystems will be profoundly damaged due a triple threat of rising temperatures, acidifying waters and oxygen starvation.
  • Ecosystems and biodiversity, such as wetlands, kelp forests, and coral reefs, are at severe risk of failure or disappearance.
  • Fisheries that feed much of the world are in critical danger of collapsing or moving beyond reach of communities that rely on them. Under business-as-usual, the report projects a 20% decline in fish catch potential on the East Coast of the United States.
  • Warming oceans and sea level rise will fuel increasingly severe extreme weather, with increased intensity, storm surge events, and flooding. 
  • There is a very high risk that permafrost thaw will set off a vicious warming feedback loop by releasing tens of thousands of carbon into the atmosphere. While there is conflicting evidence on whether such permafrost thaw may already be contributing to global warming, permafrost carbon includes methane, which is significant because of its high global warming potential.


  • There are dramatic differences between the impacts on a low-emissions pathway forward versus the impacts on a high-emissions pathway.
  • Adaptation options to many impacts will be severely compromised on the business-as-usual path, especially for some marine ecosystems including coral reefs, and Arctic and low-lying coastal communities.
  • We have to adapt to and manage the changes that we can no longer avoid, requiring tens to several hundreds of billions of dollars in investment per year. We also have to act quickly to prevent the catastrophic changes we can still prevent, such as extreme sea level rise and widespread ocean ecosystem failure.
  • Ocean-based renewable energy sources, including offshore wind, can help address climate change and generate economic opportunities.

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