How Climate Change Affects Oceans : A Review Of The IPCC Report


The Intergovernmental Panel on Climate Change (IPCC) last month released a new report, one of three special reports, the other being the land and climate report and the special report on 1.5 degrees as decided upon in 2016.  The report titled The Oceans And Cryosphere in a Changing Climate examines the effects of climate change on the world’s oceans and the cryosphere. The cryosphere is the frozen component of the earth i.e. mountaintop glaciers, polar ice caps, sea ice and icebergs as well as permafrost.
An iceberg


It starts by noting that 71% of the Earth surface is covered by oceans which also hold 97% of all the water on the planet. Now, oceans have a huge role in supporting life on Earth. They regulate gases, regulate heat and regulate climate. They also support a huge number of species and biodiversity, a good number of which are still undiscovered. They provide food and water, support tourism, trade and culture among other myriad uses.

According to the authors, the ocean will continue changing, due to the emissions in the atmosphere and their effects. It also mentions that everyone is directly or indirectly dependent on the above.

With the advent of the industrial era, increase in greenhouse gas emissions has led to higher global temperatures, something which has also affected the ocean. Oceans have absorbed about 90% of all extra heat in the atmosphere. Of note is that the ocean is actually one, but divided by land into several ‘sections’.

Herein, I explore some of the findings of this long and exhaustive report.

For a start, climate change is increasing the occurrence of marine heat waves. Marine heat waves are areas of extra hot water that spread over quite a long distance. It is just like a heat wave on land, except it’s in the ocean, over water. This extra hot water partially contributes to other effects such as oxygen loss.

The hotter or warmer the water gets, the less its capacity to dissolve oxygen. This means that marine animals dependent on oxygen to respire are gravely affected and have to migrate.

Hotter water also increases ocean stratification. The ocean is naturally stratified according to density and temperature. But as it absorbs more heat, the upper layers becomes warmer than usual. This warmer water settles on top of the colder denser water and there’s less vertical mixing. Lack of mixing prevents the spread of oxygen and other gases as well as nutrients into all of the ocean. Animals and plants dependent on such will therefore be negatively impacted.

The other effect of climate change is that some species of algae flourish in warmer water. Such algal blooms are harmful and can be poisonous when consumed[1] or when in contact with the human skin.

Sea level rise  is also another consequence of climate change that portends danger. Sea level rise is caused by thermal expansion of water in the ocean as well as the addition of freshwater from melting polar ice caps. This rise has several consequences. One is coastal erosion. Beaches are being swallowed up by rising waters. Rising waters also submerge mangroves which are important in mitigation of climate change. Mangroves are a habitat for unique fauna and flora especially rare butterflies.

Mangroves grow in brackish water, the boundary between fresh and saline water, and in waterlogged soil.  As mangroves are increasingly swallowed up by the sea, they continue to creep inland and colonize areas previously occupied by herbaceous land plants. This displacement negatively affects the animals (fauna) that used it as a habitat

Sea level rise also threatens low lying coastal areas and island states. As a matter of fact, their very survival is at stake as invading water reduces their acreage. As per the report, more than half a billion people live in these areas. Large cities throughout the world such as New York and Lagos are under threat from the rising seas.

 Climate change also leads to higher ocean waves, which worsens erosion and causes flooding.

Higher sea surface temperatures also contribute to stronger and more intense tropical cyclones which cause damage to infrastructure and loss of lives.

As the ocean absorbs more carbon dioxide, the gas dissolves in the water and creates weak carbonic acid, thus changing ocean chemistry and affecting many species, among them corals. This is known as ocean acidification. The loss of corals due to climate change is collectively known as coral bleaching 

Higher water temperatures coupled with these changes in ocean chemistry make it near impossible for corals to survive, affecting their ability to form skeletons, as well as the calcification process. Coral reefs are important because of their ability to house a very diverse ecosystem. Coral reefs protect coastal areas from dangerous wave action, cyclones and erosion. 

Corals also support the fisheries sector. They are also a major tourist attraction and support the economy of neighboring communities.

Sea water is saline, and its intrusion inland affects freshwater aquifers which provide drinking water. It also turns previously fertile agricultural lands toxic to plants.

Hotter oceans affect the fishing industry in several ways. They decrease maximum catch potential[2]. Hotter waters are devoid of oxygen and nutrients and fish will tend to move away from such areas in search of cooler and nutrient rich areas. This is poised to alter the global fishing industry, especially for coastal communities. This will also affect the provision of seafood and it subsequent effect on human dietary needs. Countries whose economic mainstay is the blue economy[3] will be gravely affected.
A whale

Higher sea temperatures will also cause instability of Greenland and Antarctic ice sheets, thus adding more water into the oceans.

Now, when it comes to land, glaciers provide water during the hotter seasons (summer) but global warming is causing glacier retreat. This means water availability and seasonality is affected As glaciers melt, plants will colonize the empty spaces and move upwards. This will change the availability and distribution of plant and dependent animal species in alpine areas[4]

Permafrost thaw is another result of the current climate change and not only does it affect communities living in the Arctic, but also adds to the levels of carbon dioxide and methane gases in the atmosphere.

As mountain glaciers melt, snow covered peaks which are a major touristic attraction will (are) become (ing) bare. This has been witnessed in East Africa especially with the mountain tops of Mt Kenya and Kilimanjaro. This affects the livelihoods of communities dependent on it.

Glacier retreat also affects the integrity and stability of previously frozen slopes.

However, the IPCC report notes that summertime transport in the Arctic has increased in the last two decades. Is there a possibility of an ice free summer in the Arctic?

Some of the solutions proposed to the problem include:-

Creation of networks of protected areas. Apart from being climate action, it also guards against overfishing. Another solution would be the rebuilding of over exploited fisheries

Assisted species relocation is recommended for species which cannot adapt or migrate fast enough.

Coral gardening could also be a veritable response to repopulate coral reefs.

Vegetated coastal ecosystems which are gravely affected by the vagaries of a warming ocean (especially erosion) can be restored.

When put in place, early warning systems gives people time to put safety measures and structures place, and avoid preventable loss and damage, as well as save their lives.

It is also necessary to know how to climate proof infrastructure, and especially flood proof buildings.

On a larger scale, educating people on the vagaries of climate change is necessary if we are to yield any result when it comes to climate action. When people know how they are affected, they are more likely to be interested in the solutions as well.

At the same time, it is necessary to equip people with skills and capacities to mitigate as well as adapt to the ever worsening effects of climate change.

Renewable energy in the form of tidal, wave and offshore wind is also another way to mitigate climate change as well as provide energy that is clean.

However, a good number of this responses require multi- sectorial and international or regional effort in order to be effective. Cooperation among governments and organizations is a must for these policies to yield good result.

In its conclusion, the IPCC urges the overarching goal of climate action – to reduce emissions.

According to the Paris Agreement, emissions still need to peak, reach net zero[5] and then net negative[6]




[1] When sea food containing algal content is eaten – it is poisonous to human beings
[2] the amount of sea food that can be caught given the conditions
[3] The exploitation of ocean resources for economic gain without negatively affecting ocean health
[4] Places up in the mountains which are normally snow covered and there’s no plant life.
[5] Amount of emissions released equals those absorbed
[6] More emissions are absorbed than are released.

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