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Report on the Ocean and Cryosphere in a Changing Climate
IPCC, 2019

The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), published September 2019, is the first effort made by the IPCC to examine the far regions of the earth, from barren poles to mountain peaks and deep ocean valleys. This report was done to investigate the effects of climate change on areas remote to humans, describing observed and expected changes. It provides a snapshot of the latest knowledge on mountain areas, polar regions, coastal stretches, and marine environments, and describes the changes we can expect from them on a warming planet.

The subject of the report is oceans and the cryosphere. Oceans cover nearly three quarters of the earth’s surface, and hold around 97% of it’s water. The ‘cryosphere’, meanwhile, refers to the frozen parts of our planet - including glaciers and ice sheets. These regions are home to unique environments and ecosystems, and they are closely connected with other regions on earth through various geological cycles. Moreover, they are incredibly important in the services they provide to people, including food and water, cultural value, tourism, and livelihoods. The ocean and the cryosphere tend to bear the initial brunt of global warming, and so they become an important indicator of changes. The SROCC describes the effects of climate change, and their consequences, for each of the following sections.

I. High Mountain Areas

Climate change has caused a significant decline in snow cover, glacier size, and permafrost levels in recent years. Seasonal runoff from melting glaciers and snow is crucial to millions of people around the world living in high mountain regions, providing fresh water supply, irrigation for fields, and an energy source to be harnessed with hydroelectric dams. Decreased snow cover means less seasonal runoff, compromising the living conditions of people who depend on these services. Moreover, these same alterations are significantly shifting the composition of high mountain ecosystems. Warmer temperatures allow the movement of previously absent species into higher altitudes, while the survival of some cold-adapted species is threatened. Sadly, with the path we are on, snow cover, glaciers, and permafrost will continue to decline throughout the 21st century. This means a further decline in water supply to high altitude communities and potential extinction of unique cold-adapted species, such as trout and snowshoe hare. Adaptation strategies exist in some regions to combat shortages in water supply from declining snow cover and runoff, including building synthetic ice reservoirs. Yet, to maintain the integrity of high mountain areas, the report calls for effective and cooperative governance based on a diverse cultural background as well as scientific knowledge. Moreover, it asserts the need to strengthen international treaties and conventions to protect the high mountains. Evidently, the mountains are a unique and important component of global ecosystems, and are heavily impacted by climate change.

II. Polar Regions

The general term ‘polar regions’ encompasses everything beyond the arctic and Antarctic circles, including both the Arctic and Antarctic ocean as well as the associated ice masses. Polar regions experience some of the most significant impacts of climate change. Indeed, they have been warming at more than twice the global average over the past several decades. This coincides with increased air temperature and decreased ice coverage in these areas, as well as a decrease in habitat for ice dependent and cold-adapted species causing a shift in polar biodiversity. Moreover, mass loss of glacier ice has contributed to sea-level rise. Because of these effects, shipping traffic has increased through previously ice-covered seas, leading to increased economic opportunity in the areas (for fishing and tourism) but potentially detrimental effects for further ice loss and species survival. These effects are only expected to get worse over time, with polar sea ice declining, glaciers melting, sea levels rising, shifting biodiversity, and permafrost thawing. Mitigation of and adaptation to climate change at our poles will require innovative, long-term strategies planned in coordination with local arctic communities.

III. Sea Level Rise and Implications for Coastal Settings

This chapter assesses the risks of rising sea level and coastal extreme weather for communities lying close to water level. Global mean sea level has been rising at an increasing rate, currently at 3.6 mm/year. Melting glacier ice due to global warming is the major cause of this rise. Higher sea levels will increase the frequency of what the authors call ‘extreme sea level events’, which include large-scale flooding and intense tropical storms. These events, which are now considerably rare, are expected to occur much more often as the sea continues to rise. Coastal ecosystems are expected to suffer as a result, through loss of habitat and extinction of important species. Sadly, the report acknowledges that even if emissions are lowered to meet the Paris targets, sea level rise will still be accelerating into the next century. Many coastal communities could be lost to the sea, sparking waves of migration. So, several options are outlined for low lying communities to adapt to rising sea levels in the future. These include physical barriers to protect against floods and severe weather, ecosystem conservation, and extension of cities into the sea to mitigate land loss. However, the authors also recognize that these efforts will be easier in richer countries and cities; therefore, they conclude that adaptation to rising sea levels will require significant intergovernmental cooperation and planning far in advance to keep impacts to a minimum.

IV. Marine Ecosystems

The ocean is necessary for almost every aspect of human life and we rely on it to maintain a stable temperature, provide essential nutrients, and circulate water. Moreover, the oceans contain a wealth of biological diversity, upon which the economic success of millions of people depends. Unfortunately, it seems that carbon emissions and global warming are now threatening these resources. The oceans have been steadily warming for several decades, and the rate of warming seems to be increasing. Moreover, oceans are taking up carbon dioxide, leading to acidification at a rate of up to 0.03 pH units per year. An effect of acidification is loss of oxygen in the ocean, which has been occuring at alarming rates. These changes to the ocean greatly impact marine biodiversity. Changing temperatures shift and restrict habitats of marine organisms, from plankton to whales - for example, tropical species have begun to shift further north. Acidification impacts the ability of corals and other similar organisms to create their skeletons, because the calcium carbonate they use reacts with carbon dioxide to form acid. Additionally, warmer temperatures promote large blooms of algae, which tend to use up all the oxygen and other nutrients in that area. Because of these, the report projects that overall numbers of fish and marine mammals will decrease in the future, and that coral reefs will become severely impaired above two degrees of warming. The best mitigation option is to decrease emissions and prevent further warming and acidification.

V. Extremes and Managing Risks

The last section of SROCC deals with future projections - what will ocean and cryosphere warming look like, and how humans might adapt to or mitigate these effects. As far as changes to the ocean surface, it seems that our seas will get rougher, storms will on average be more severe, and the frequency of marine heatwaves (periods of abnormally warm water) will increase. Warmer waters will weaken the temperature-driven ocean water circulation in the Atlantic ocean, decreasing the cycling of nutrients between the arctic and the equator. Further, seasonal weather events like El Nino will intensify, driving greater fluctuations in global weather patterns. So what should we do about all this? First and foremost, the authors report that reducing emissions will directly limit global warming and lower the risk of glacier melts, marine heatwave occurrence, and coral reef degradation. Secondly, risk-reduction measures like flood barriers and early warning systems for weather events will help to limit the damage of the warming oceans and cryosphere. Overall, this section concludes by saying that countries who are better prepared for these impacts will fare better as the world warms.

The SROCC is the third and last IPCC special report of the 6th assessment cycle. It demonstrates clearly that at the current rate, negative impacts of climate change to the oceans and cryosphere are inevitable; but, forceful preventative and risk-reduction measures could help avoid some of the worst effects.

Find the full report here.


1. Intergovernmental Panel on Climate Change (ICC). IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. IPCC, 2019, available from

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