5 ways climate change is affecting our oceans

Rod Fujita

Editor’s note: This post was updated on Aug. 23, 2018

Climate change is taking a toll on forests, farms, freshwater sources and the economy – but ocean ecosystems remain the epicenter of global warming.

Even with their vast capacity to absorb heat and carbon dioxide, oceans were 0.17 degrees Celsius (0.3 degrees Fahrenheit) warmer in 2017 than in 2000, and the warming trend appears to be accelerating. More than 90 percent of Earth’s warming since 1950 occurred in oceans, so it’s easy to see why scientists are concerned.

Here are five ways these ever-warmer temperatures are affecting our oceans:

1. Coral bleaching

As early as 1990, coral reef expert Tom Goreau and I pointed out that mass coral bleaching events observed during the 1980’s were probably due to anomalously warm temperatures related to climate change.

It’s now evident that many coral reefs, including Australia’s Great Barrier Reef, are dying. Mass coral bleaching results in the starvation, shrinkage and death of the corals that support the thousands of species that live on coral reefs.

Coral reefs are particularly sensitive to increases in temperature. And new research shows that oceans are now experiencing longer and more severe “marine heat waves” that could push even more ocean animals and ecosystems to their limits.


2. Fish migration

In addition, many fish species are moving toward the poles in response to ocean warming, disrupting fisheries around the world.

A recent study predicts that climate change will force hundreds of ocean fish northward, hitting North American fisheries that depend on Pacific rockfish, Atlantic cod and black sea bass especially hard.

3. Drowning wetlands

Rising sea levels, partly the result of heat absorbed by the ocean, is also “drowning” wetlands. Such areas normally grow vertically fast enough to keep up with higher water levels. But recently, this rise has accelerated to the point where wetlands can no longer keep their blades above water.

Coral reefs and sea grass meadows are also in danger of “drowning” since they can only photosynthesize in relatively shallow water.

Whether wetlands, coral reefs and seagrass meadows can keep up with rising seas will depend on many factors, however, including how healthy they are and how clean the water is.

4. Ocean acidification

Oceans today absorb about one-third of the carbon dioxide humans send into the atmosphere, about 22 million tons a day.

This great service, which has substantially slowed global warming, has been accomplished at great cost: The trend in ocean acidification is about 30 times greater than natural variation, and average surface ocean pH, the standard measure of acidity, has dropped by 0.1 unit.

That’s a 25-percent increase in acidity, which is significant.

Higher acidity is damaging many ocean species that use calcium carbonate to form their skeletons and shells. Studies have shown that calcium carbonate formation is disrupted if water becomes too acidic.

Ocean acidification also appears to be affecting whole ecosystems, such as coral reefs, which depend on the formation of calcium carbonate to build reef structure, which in turn provides homes for reef organisms.

5. A disastrous positive feedback loop

Finally, acidification also appears to be reducing the amount of sulfur flowing out of the ocean into the atmosphere. This reduces reflection of solar radiation back into space, resulting in even more warming.

This is the kind of positive feedback loop that could result in run-away climate change – and of course, even more disastrous effects on the ocean.

Oceans are at the brink

For decades, the ocean has been absorbing carbon dioxide dumped into the atmosphere by burning fossil fuels, faithfully capturing the extra heat that elevated atmospheric carbon dioxide levels produce.

But even the ocean has limits. We are bumping up against them now, with damaging consequences for the whole world.


When fossil fuels are burned heat is released (that's why we burn them). In addition carbon dioxide is released as a by-product. The heat emitted by our energy use is four times the amount required to account for the measured rise in atmospheric temperature and is a more rational explanation for the heat effects we see than models based on CO2 concentrations. As to the acidification of the ocean, I offer without proof, the possibility/probability that acid rain from burning of coal with its sulfur content is the cause of lowered pH. The change in hydrogen ion content is so low that an equivalent increase in sulfate ion could not be detected with accuracy.

Philip Haddad
October 8, 2013 at 9:46 pm

Does not help me at all.

May 16, 2018 at 6:10 pm

If this doesn't help you then go somewhere else. You don't need to tell people this didn't help you when it is simply informing you on how climate change is affecting our oceans, IN WHICH OVER 70% OF OUR EARTH IS OCEAN. So why don't you go to another website. Your ignorance is not needed here.

November 19, 2018 at 2:07 pm

In reply to by Alvena

We need to save the Earthhhhhhhhhhhhh.

May 21, 2018 at 9:12 pm

Yeah we do

September 19, 2018 at 11:38 am

In reply to by vanessa

Sort of sad how many animals die due to climate change and its all our fault.

May 26, 2018 at 8:27 pm

this was very helpful, we need to save our oceans !

May 28, 2018 at 12:19 am

I would like the EDF to challenge President Trump on his denial of anthropogenic climate change. To ask him on what basis of fact does he base his belief that it is not caused by mankind.

Tom Cowart
June 12, 2018 at 10:40 pm

I would like you to tell them.

Joel Cunningham
August 8, 2018 at 12:11 am

In reply to by Tom Cowart

I want that to happen. I also want him to get impeached.

November 7, 2018 at 4:54 pm

In reply to by Tom Cowart


Kikimi Bottom
July 16, 2018 at 1:30 pm

A point of interest…it is said that the world will go this direction: 1/3 of all living creatures on the land, sea and earth will perish. Man’s disregard for Mother Earth and desire to have more will bring disaster. So if you haven’t yet looked into scripture maybe it’s time. Just a thought… Let’s hope there is a solution though…

Bobby G
August 13, 2018 at 1:04 pm

I don't see how reading the scripture is a help, much of the problems we face are a direct result of greed. Greed is a result of the scripture's message. We'd be much better off if we quit acquiring 'stuff'.
Less is more.

September 9, 2018 at 3:36 pm

In reply to by Bobby G

Explain how the melting ice can cause the weather to worsen and expand the ocean?

How is the weather getting more extreme? Explain.

Does climate change affect plants and animals? Give some details in your explanation.

What is the relation between global warming and the ocean?


November 8, 2018 at 10:28 am

A lot to explore here — and this is a start! https://www.edf.org/climate/climate-change-and-extreme-weather

Karin Rives
November 9, 2018 at 10:33 am

In reply to by RealNXGGAXXL

ITS ALL OUR FAULTS!!! SAVE THE OCEANS!!!! Sea creatures lives matter too, y’know.

hailey smith
November 9, 2018 at 1:06 pm

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