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SDG 14 – Oceans, our Climate Buffers

“Conserve and sustainably use the oceans, seas and marine resources for sustainable development.”

Understanding the Goal

SDG 14 addresses many important aspects of why it is necessary to treat our oceans, their animals, and plants fairly and sustainably. What the goal does not address at all is the importance of the oceans for our global weather and the reduction of greenhouse gases. 

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Now, of course, one could say that compliance with the 7+ action sub-measures will ultimately ensure that the oceans can continue to do their “jobs” as weather gods and climate protectors par excellence. 

But it is not that simple! And this is precisely where the immaturity of SDG 14 lies. People do realise that there are animal and plant species worth protecting in the ocean, and that it should not be polluted or overfished. But one very most important thing is missing – the all-encompassing framework of why exactly the oceans themselves are vital for the survival of all living being on the world. 

The world’s oceans are an important buffer in the climate system.

Currently, oceans cover 71% of our planet, represent 95% of the living biosphere and contain 97% of all water on our planet. Without the complex structure of the world’s oceans consisting of water bodies and current systems, without their productivity, their cycles and interactions with the atmosphere, our life today would be unimaginable. 

Our global climate is influenced by the oceans in several respects:

  1. they balance the temperatures
  2. they are our most important CO2 buffer

Oceans as Temperature-Balancers and Climate-Directors

Oceans and their various surface currents, together with the circulation system of the atmosphere, form our global climate circulation system. Together they are the most important factors for global temperature exchange. They ensure that it does not get too cold in the higher latitudes and too warm in the lower. 

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Dr. Michael Pidwirny

The surface currents of the oceans (e.g. the Gulf Stream), mostly driven by the wind, are deflected by the Coriolis force to the right in the northern hemisphere and to the left in the southern hemisphere in order to flow back along the edges of the continents. They transport warm water from the radiant lower latitudes to the higher latitudes, where it cools down and flows back again. 

An example: Due to the sinking of large water masses in the north, the North Atlantic leads to a subsequent transport of warm water in the North Atlantic Current to Western Europe. This leads to much higher temperatures there than corresponds to the mean value of these latitudes. For centuries, this has had a major impact on humans and their development as well as on vegetation. 

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Global warming, however, is causing our oceans to change. They are heating up. If the temperature in the air and water rises, the polar ice caps melt. This causes the water level to rise and, more important, leads to a decrease in the salinity of the oceans. The oceans change their PH value and become “sweeter”. According to researchers, this could slow down, redirect, or even paralyse ocean currents. We can already see that the observed weakening of the Atlantic circulation has led to a cooling of sea surface temperatures in parts of the North Atlantic. In Europe, it is getting colder.

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The number and intensity of hurricanes could also increase, as they draw their energy from warm surface temperatures. Likewise, continental weather patterns, meaning the formation of high-pressure and low-pressure areas, are significantly influenced by the behaviour of ocean currents. Extreme weathers are the result, bringing droughts, floods, or strong winds. In many parts of the world, these changes have become more and more frequent in recent years.

Oceans as Carbon Buffers 

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In addition to balancing the temperature, our oceans also serve as carbon dioxide reservoirs. They are the largest we have. Since the industrial revolution, our oceans have absorbed 11.8 billion tonnes of human-made CO2. 

But how do oceans absorb CO2? Specifically, in two steps: First, the CO2 dissolves in the surface water. Ocean currents and mixing processes then ensure that the dissolved CO2 is transported from the surface deep into the ocean basins. There, the carbon can remain for long periods of time and accumulate. Therefore, deep water is considered a crucial carbon sink for the Earth – and an important counterpart for anthropogenic greenhouse gas emissions.

Riccardo Pravettoni, UNEP/GRID-Arendal

Without the oceans, atmospheric CO2 would be higher today and human-made climate change would be correspondingly stronger.

Now, however, CO-emissions and thus atmospheric CO2 levels have risen considerably since measurements were taken in the early 1990s. Nevertheless, according to Nicolas Gruber, head of a research team at ETH Zurich, the oceans have been able to keep pace. During numerous measuring trips between the years 1994 and 2007, he found out that the oceans absorbed 34 billion tonnes of CO2 from human production in this period. 

Between 1997 and 2007, the oceans swallowed about 2.6 gigatonnes of CO2 per year – 31% of the total man-made CO2 emissions during this period.

(Nicolas Gruber, ETH Zurich)

The amazing thing: Despite the massive increase in CO-emissions, the percentage absorbed by seawater was roughly the same as in the decades since industrialisation. So, we can say that this CO2 reservoir is still functioning quite well. 

So far, the ocean’s performance as a CO2 sink has developed in proportion to the atmospheric concentration of CO2.

But it is uncertain how long this will remain the case. This is because the warming of the oceans is creating fewer cold-water masses that could sink to the depths. This reduces the transport of carbon into the deeper ocean through the so-called “physical pump”. Thus, the measurements show that although in percentage terms the oceans are still absorbing as much CO2 as they did 100 years ago, a large part of the absorbed CO2 now remains in the upper water layers: Only about 7% of anthropogenic carbon is present in great water depths below 2000 metres. Our oceans could therefore soon be “saturated”.

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In sum, there is justified criticism of the formulation of SDG 14. In addition to the protection of living creatures in the water, the protection of the oceans, as our climate regulators, must also be addressed. If these systems collapse, the weather will go mad, and the most reliable and sustainable CO2 reservoir will be destroyed. Here, improvements must be made, creating an understanding of how important our oceans are for climate change and the continued existence of all life on earth.

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