From a climate point of view, protecting the oceans is like building solar panels and taking cars off the road. 

Climate change conjures images of traffic-choked cities and power station chimneys, or bedraggled polar bears and oil spills.

But we often forget about the enormous power of natural systems like oceans that help keep the climate stable – and that means we don’t look after them as well as we should. 

Whether we choose to protect or plunder the oceans will go a long way to deciding how climate change plays out, so let’s dive in and find out how it’s all connected.

Microscopic marine plants guzzle CO2

Healthy oceans are amazing at taking carbon dioxide out of the air and locking it away in its depths. This process starts when tiny floating plants called phytoplankton suck carbon dioxide out of the air as they grow.

As animals (like krill) eat the phytoplankton, and other animals (like whales) eat those animals in turn, that carbon moves through the food chain until an animal dies and sinks to the bottom of the sea. (Sadly the circle of life doesn’t always involve cute lion cubs).


Although they’re invisible to the naked eye and probably won’t ever star in multiple Disney movies, phytoplankton have strength in numbers. Globally, they absorb billions of tonnes of CO2 each year – that’s a huge slice of our emissions cancelled out, all thanks to the oceans. And because healthy oceans support more life, creating ocean sanctuaries can help to maximise this carbon-busting effect.

And seawater carries it away

But that’s just the start. CO2 naturally dissolves into seawater, is pulled by ocean currents down to the depths and kept out of the atmosphere for the long term.


Because the process happens slowly and over a huge area, the effect is harder to measure than phytoplankton’s hard work. And because there’s already too much carbon in the atmosphere, it causes problems for ocean life by making seawater more acidic, so we shouldn’t be too quick to celebrate it. But there’s no question that it’s locking away a huge amount of CO2 that would otherwise be causing trouble up in the atmosphere. 

This process is a powerful example of how the climate and oceans relationship is a two-way street: tackling climate change is good for the oceans, and protecting the oceans is good for the climate.

But we can’t take it for granted

Without these currents, and phytoplankton absorbing carbon, the world would be too hot to inhabit. We can’t take their help for granted – if the oceans’ natural systems breaks down far enough (and we’ve already pushed them way too close to the edge), they’ll stop storing carbon and start releasing it, at which point we’ll be in all kinds of trouble.

The oceans store extra heat from global warming

The oceans absorb huge amounts of heat from the atmosphere, keeping the land much cooler than it would be otherwise. Scientists think that of all the extra heat generated by climate change, more than 90% has been absorbed by the oceans. 

But that comes at a cost too

Humans have been spared a huge amount of suffering through avoided droughts and heatwaves, but it can’t go on forever – and already it comes at a cost. Adding such an enormous amount of heat and carbon to the ocean system is already hurting sea creatures, supercharging storms, destroying natural wonders like the Great Barrier Reef, and messing up other crucial life-support systems. And because water expands as it warms up, more heat means rising sea levels, putting low-lying islands and coastal cities in danger. 


Many of us are motivated to protect the oceans because we care about whales, turtles, dolphins and other wildlife – and of course that’s a good enough reason by itself – but knowing how much the oceans do to keep our climate stable makes this work we’re doing together even more important.

Like nearly everything to do with the environment, the story of oceans and climate change is full of connections and overlaps but the moral of the story is clear. To protect the oceans, we need to tackle climate change. And to tackle climate change, we need to protect the oceans. 


Let’s get to work.

Malachi Chadwick is an Oceans Campaigner at Greenpeace UK.