how the climate crisis is destroying our oceans

The climate crisis has become tangible. Its effects on the world's oceans remain invisible at first - and yet they are dramatic.

Mother and child by the sea

This year at the latest, we have all noticed: climate change is here. Heavy rain and flooding in large parts of Germany, heat waves in southern Europe, and a new record: July was the warmest month ever recorded worldwide, reports the US climate agency NOAA. What consequences does this have for the oceans - and thus for us?

Current global warming is already 1.2 degrees and in all likelihood we will crack the 1.5 degree mark as early as 2030 - and quickly go beyond. Even a containment to 2 degrees can currently only be achieved with rapid and massive changes.

What consequences does the climate crisis have for us humans?

Basically, it is clear: weather extremes are increasing. Heat waves, rain - all this has happened before, but the intensity and duration is changing. Biodiversity is decreasing, sea levels are rising. People will lose their homes due to climate change. We do not yet know exactly to what extent all this will happen.

Climate crisis: Heavy rainfall events on the rise.

On the one hand, this depends on how global greenhouse gas emissions develop - in other words, how quickly we apply the brakes - and on the other hand, our planet is a very complex ecosystem with many interconnections and interactions. It is difficult to calculate all the consequences.

However, many effects are considered certain. They could be observed in the past decades and/or reproduced in laboratory studies. Based on these results, the Intergovernmental Panel on Climate Change (IPCC ) presents model calculations that depict the probable effects of further temperature increases - depending on how quickly we manage to drastically reduce our CO2 emissions.

Let's first look here at what impact the climate crisis is having on our oceans.

Impacts on the oceans: Rising sea levels

Arctic sea ice and glaciers are melting, causing sea levels to rise. We have already irrevocably set this process in motion and it has developed its own momentum:

For one thing, sea levels will continue to rise even if we contain the global temperature increase to 2 degrees; for another, this process is accelerating.

Currently, sea levels are already about 20 centimetres higher than they were in 1901. The IPCC has calculated several models, and even the most optimistic (and rather unrealistic) assumes a further rise of about 30-50 centimetres by 2100. But with stronger temperature increases, the rise by the end of the century could be as much as a metre - or even more.

Global warming is melting glaciers and raising sea levels.

But even after 2100, the mirror will continue to rise. The Süddeutsche Zeitung writes in August 2021:

"The long-term forecasts are also drastic: over the next 2000 years, sea level rise is likely to be two to three metres if the 1.5-degree target is still achieved. In the other extreme case, with barely curbed emissions and up to five degrees of long-term warming, it could be as much as 22 metres."

"In the extreme case, with five degrees of long-term warming, it could be up to 22 metres of sea level rise."

-Süddeutsche Zeitung

The first, direct consequence is, of course, that large areas of land disappear into the water. This affects shallow coastal regions, for example in Germany and Poland, and threatens entire countries like Bangladesh or islands like the Maldives.

The people who inhabit these regions become climate refugees. This not only represents countless personal fates, but also poses a challenge to the host regions and countries.

Impacts on the oceans: slowing of the Gulf Stream

However, the melted ice from Greenland has other effects: It is fresh water, so it has a different density than the salty seawater and contributes significantly to the slowing down of the Gulf Stream, which supplies Europe with a lot of heat energy - without it, it would be around five to ten degrees colder on our continent.

"Without the Gulf Stream, the Elbe estuary and the North Sea would be iced over for months, much like Hudson Bay in Canada, for example, which lies at the same latitude"


Scientists have long warned that the Gulf Stream could come to a standstill. The latest findings not only confirm this fear, but also suggest that this could happen more quickly than previously expected.

It is not yet possible to estimate exactly what this means for us. It is possible that the heat waves would remain, but that there would also be severe cold spells. "An alternation of dry and rainy seasons in Germany would be possible. That would be a major stress test for the German forests and would pose huge challenges for agriculture - and thus have a direct impact on people," says meteorologist Karsten Schwanke.

Effects on the oceans: Rising temperature

Not only are the air and earth warming, but the oceans themselves are also getting warmer on average. This also leads to more severe severe weather events: "Heated oceans tend to carry away heat via often devastating storms, leading to stronger hurricanes with more rainfall." (Source:

Corals are suffering massively from climate change.

At the same time, the rising temperature has an impact on marine life: many fish species such as mackerel and herring, for example, migrate from the North Sea to cooler waters to follow their food source - small crustaceans. They, in turn, are followed by animals such as turtles and seabirds.

If fish stocks change locally, this does not leave without Consequences for fisheries and economic sectors dependent on them. This is also because pathogens spread more quickly in warmer water. This further decimates animal and plant populations, and can also be dangerous for humans.

The famous coral reefs - ecosystems with many animal and plant species - also suffer massively from the increased water temperatures. Coral reefs first lose their unique colours (this is called coral bleaching ) and eventually die completely. This can also be observed again and again on the famous Great Barrier Reef.

The warming of the oceans is not taking place evenly - especially the water surface is getting warmer and in some places hardly mixes with deeper water layers. The result is a lack of oxygen and so-called "death zones" where hardly any life is possible. From 2008 to 2019 alone, their number has increased from around 400 to about 700, many of which are also in the North Sea and Baltic Sea.

Effects on the oceans: Higher CO2 concentration

Not only the air, but also the oceans absorb a lot of CO2 and thus become acidic. This in turn attacks the calcareous protective shells of mussels, starfish, corals and crabs, whose population is reduced.

This is particularly serious because they are the first link in a long chain: If their population is reduced, an important source of food for many other marine creatures is lost, which in turn serve as food for the next species - the final loss of biodiversity due to CO2 concentration is thus far greater, and entire ecosystems are thrown out of balance.

An increased CO2 concentration in the water attacks the protective shell of starfish.

The ocean as a CO2 sink

Our oceans have always functioned as CO2 reservoirs: part of the carbon dioxide concentration in the air reaches the sea, ocean currents bring the CO2 from the surface deep into the ocean basins, where it accumulates.

So far, the ocean is thus significantly weakening global warming - with the above-mentioned consequences for marine life.
However, this effect is limited, the CO2 concentration will saturate one day. It is impossible to say when this point will be reached. What is clear, however, is that if the ocean ceases to be a CO2 reservoir, the quantities of CO2 emitted will have an even more serious effect on global warming than they already do.


Climate change is already noticeable today, yet we are only experiencing the beginnings. The massive emission of CO2 is having a massive impact on our oceans:

- the sea level rises
- the pH value changes, the seas become acidic
- water temperature rises
- ocean currents, such as the Gulf Stream, slow down

These developments contribute massively to a loss of animal and plant species, upset ecosystems and change the climate on land. Due to weather extremes and flooding, people will lose their homes (climate refugees).

Climate change cannot be stopped, but the effects can still be limited - if politics and society take immediate and effective action.