Climate Change Poses a Threat to Our Oceans


By Isabella Lövin

In 2016, the First Global Integrated Marine Assessment, also known as the World Ocean Assessment I, was published. The introduction of the report is fascinating. It states that 70 per cent of the planet's surface is covered by water and that the average depth is 4,000 metres. These oceans contain 97 per cent of all water on Earth, which is the equivalent of approximately 1.3 billion cubic kilometres. This can seem like an infinite amount.

But the report also states that there are now more than 7 billion people on Earth. If we divided all of this water equally between us, we would only have one fifth of a cubic kilometre each. And in 2050, when there will be some 10 billion people on Earth, we will only have one eighth of a cubic kilometre per person. This relatively small amount of water is what will provide each person with all ecosystem services, including food and oxygen. But this is also where some of our emissions, our waste and our rubbish will end up.

Oceans, however, happen to be borderless and are also unevenly distributed across the planet. We cannot protect our share of the ocean with walls; instead, we must cooperate in a spirit of solidarity if we are to succeed in preserving and protecting the water that we have at our joint disposal. We must work together with our closest neighbours and cooperate at a global level, between countries.

The importance of the 2030 Agenda and the 17 Sustainable Development Goals (SDGs) cannot be stressed enough. They light our way through the darkness that is currently shrouding the world. Progress is being made on many of the SDGs, but one of the goals for which developments are unfortunately moving in the wrong direction is SDG 14, which calls on the international community to "conserve and sustainably use the oceans, seas and marine resources for sustainable development".

This is why the Government of Sweden, together with the Government of Fiji, took the initiative to host the Ocean Conference in New York in June 2017. The Conference will be the first high-level forum to focus on one single goal in the 2030 Agenda, and we are enthusiastic to see growing engagement among the countries of the world.

One of the many issues demanding immediate attention at the Conference is the impact of climate change on the global marine environment. Although the ocean is the single largest habitat on our planet and is a system that is inextricably linked to human survival, climate change and the impact of increasing carbon dioxide emissions on the oceans have been largely overshadowed in the climate change debate. The oceans—which produce half of all our oxygen, regulate the Earth's climate and temperature, give us food and water, and are home to hundreds of thousands of species-have for a long time been our best ally in efforts to curb climate change. More than 93 per cent1 of all the heat people have added to the planet since the 1950s has been absorbed by the oceans—but at a price we are just beginning to understand. Rising ocean temperatures and increased acidification are now becoming apparent in melting Arctic sea ice and coral bleaching. Immediate action is needed here and we must use our entire toolbox at once: mitigation, protection, restoration and adaptation.

The warming of the oceans over the past 60 years has taken place on such a scale that it is difficult to take in. A 2015 analysis produced by the Grantham Institute shows that if the same amount of heat that was added to the top two kilometres of the oceans between 1955 and 2010 had instead been added to the bottom ten kilometres of the atmosphere, we would have seen the temperature on Earth rise by 36 degrees Celsius. So the oceans have protected us from the worst effects of climate change. But there is great uncertainty regarding the ability of the ocean to absorb carbon dioxide in future. If the oceans have so far been our best friend, there is now the risk in the foreseeable future that they will begin to send us the bill: a large proportion of the emissions we have caused since the 1900s, now stored in the oceans, may return to the atmosphere.

Ocean acidification can be called the chemical crisis of the global climate. Alongside global warming, ocean acidification risks pushing marine life beyond catastrophic limits. Since industrialization, acidification of ocean surface water has increased by almost 30 per cent.2 Coral reefs will be one of the most immediate victims of climate change if we do not take action very quickly. Although coral reefs make up just 1 per cent of the surface of the oceans, as much as 25 per cent of marine species are dependent on them. The breakdown of coral reef ecosystems also affects the protection of coastal zones, fisheries and tourism. Without a drastic reduction in carbon dioxide emissions, by 2050 almost all of the world's coral reefs may have been subjected to such acidic conditions that they will be only marginally able to form calcium and continue growing.

Researchers have estimated that the oceans are home to up to 1 million different species.3 Increased ocean temperatures risk causing the mass migration of species, resulting in the global homogenization of biodiversity. This would mean a decline in the numbers of species in the warmer water regions and a drastic increase in the colder regions around the poles. This kind of change could have a very serious impact on global fisheries and aquaculture. The Food and Agriculture Organization of the United Nations estimates that fish now account for 20 per cent of the animal protein source for around 3 billion people. Along with population growth, poor fisheries management and increased fish exports, changes in the local fish fauna can have enormous consequences for food security, especially in poor coastal countries where many people depend on fishing for their daily living.

Climate change also threatens the supply of oxygen in the oceans in two different ways. Firstly, warm water cannot hold as much oxygen as cold water, so as the oceans warm up, oxygen levels drop. Secondly, warmer water has lower density, making it more difficult for the oxygen-rich water near the surface to sink and circulate. Consequently, deep oceans face a particularly great risk of oxygen depletion. Fish that are dependent on oxygen will grow more slowly, decrease in size and reproduce less. Larger fish such as tuna, swordfish and shark, which are dependent on a large amount of oxygen, will be driven to more oxygen-rich surface waters, as will a large proportion of their prey. This will lead to increased food competition. Creatures living in or on the seabed will also need to seek out shallower waters. The knock-on effect of this will be a clear risk of even more overfishing, as more sea creatures will inhabit smaller and more easily accessible areas, becoming more readily fished.

One example of a 'hot spot' for the effects of climate change on oceans is the Arctic. Here, both warming and acidification are occurring particularly rapidly and to a greater extent than in many other places in the world. Scientific findings show an increased risk of crossing large-scale tipping points in the Arctic, such as the collapse of summer sea ice, melting ice sheets and methane emissions from melting permafrost, which may all have very significant global consequences-not least with regard to rising sea levels. The biodiversity and ecosystems in the Arctic are irreplaceable assets of global importance. Many Arctic species, ecosystems and habitats are at risk of disappearing completely, or remaining only as isolated fragments. As the ice sheet melts, increasingly large areas in the Arctic are now opening up for shipping and extracting natural resources such as oil, gas and fish. In November 2016, the planet sent perhaps its clearest warning yet, when the temperature in the Arctic was measured at a shocking 20 degrees Celsius warmer than what is normal for that time of year. The abrupt warming of the Arctic entails a dramatic change in life conditions not only around the North Pole, but also for the rest of the planet. Permanent ice at the North and the South Poles is a prerequisite for a stable planet. A self-heating Arctic will have major effects on global climate. Let us therefore hope that this was the last alarm bell from the planet before we humans came together and succeeded in reversing the trend.

It is impossible to estimate the economic value of living oceans for us humans; they are in essence the actual prerequisite for human existence. It is beyond doubt, however, that the effects of climate change on the oceans will entail major economic costs. For example, the cost of reduced tourism due to coral bleaching has been estimated to be as much as $12 billion annually. If lost ecosystem services from reefs are included, the annual cost is estimated to reach $1 trillion by the year 2100.4 But the truly great costs will be measured in the form of reduced human health and security.

Keeping global warming well below 2 degrees Celsius, and aspiring to 1.5 degrees Celsius under the Paris Agreement, is fundamental to mitigating the impact of climate change on our oceans. Sweden is prepared to take a leading role in international climate efforts and has the goal of being one of the world's first fossil-free welfare nations. Sweden has also doubled its contributions to multilateral climate financing in recent years and is now the largest per capita donor to many of the multilateral climate funds, including the Green Climate Fund, the Global Environment Facility and the Adaptation Fund. Climate change is also central to much of Sweden's bilateral cooperation and we want to work proactively to strengthen initiatives that are linked to the impact on oceans. Immediate and dramatic cuts in carbon dioxide emissions will buy us time to strengthen the resilience of oceans, ecosystems and species, that is, their ability to adapt to the negative impact of climate change and the inevitable stressors already in operation in our oceans. Fish that can easily migrate will be able to find new habitats, and organisms with short reproductive cycles such as plankton can evolve to adapt to the new conditions.

Drastic measures must be employed to strengthen the protection of biodiversity and ecosystems. It is still possible to preserve large, relatively unaffected marine ecosystems if measures are taken now. Sweden has allocated substantial funds to protect valuable marine environments in national waters and meet the commitments under the Convention on Biological Diversity, but protection of marine environments is also an important issue in regional and international cooperation. Moreover, the impacts of climate change must be considered in assessments of threatened species and in formulating advice on which measures need to be taken.

In the light of the various stress factors acting on our oceans, the sustainable management of marine resources-not least measures to ensure improved food security—is more important than ever. Forceful measures are essential to stop overfishing and illegal fishing, and ensure a move from industrial fishing to small-scale fishing in coastal nations where many people are dependent on fish for their daily living. Further forceful measures are necessary to prevent and reduce marine pollution, including marine debris and the inflow of nutrients. Finally, we must also invest more in research to increase our scientific knowledge in all these areas.

The impact of climate change on our oceans can no longer be described in isolated, individual stories about bleached coral reefs; it involves fundamental changes to ecosystems and marine life on a scale we are only just beginning to imagine. We must act now and put oceans at the centre of our climate efforts. The great interest in the Ocean Conference from all parts of the United Nations system, the science and business sectors, and civil society demonstrates that the international community is ready to take forceful action.  


1    Sydney Levitus and others, "World ocean heat content and thermosteric sea level change (0-2000m), 1955-2010", Geophysical Research Letters, vol. 39, No. 10 (17 May 2012).

2    Richard A. Feely, Scott C. Doney and Sarah R. Cooley, "Ocean acidification: present conditions and future changes in a high-CO2 world", Oceanography, vol. 22, No. 4 (December 2009), pp. 36-47.

3    Ward Appeltans and others, "The magnitude of global marine species diversity'', Current Biology, vol. 22, No. 23 (4 December 2012), pp. 2189-2202.

4    Jean-Pierre Gattuso and others, "Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios", Science, vol. 349, No. 6243, (3 July 2015), pp. aac.4722-1-4722-10.