It Was Never Mankind vs. the Ocean: We Are Overworking Earth’s Largest Climate Regulator

We emit. The ocean absorbs. We get the benefit. The ocean carries the cost.

Marine pollution. Rising sea levels, biodiversity loss.

We often talk about the ocean as a victim of climate change. And it is. But that framing misses half the story.

The ocean is also one reason we have not yet experienced the full force of the climate crisis.

It absorbs heat, stores carbon and moves energy around the planet. It regulates temperatures, rainfall and weather systems far beyond our coastlines. In other words, the ocean is not simply being affected by climate change. It is doing a remarkable amount of the work of buffering us from it.

And it continues to do that work while absorbing the consequences.

The Heat Account

Here is a number worth sitting with:

The ocean has absorbed more than 90% of the excess heat trapped in the climate system by human-caused greenhouse gas emissions.

More than 90%.

We already talk about how rapidly the climate is changing. But it is changing at this pace while the ocean is absorbing the overwhelming majority of that additional heat.

Without that buffering, much more of the excess heat would remain in the atmosphere and on land.

Water can absorb enormous amounts of heat without warming as rapidly as land. Ocean circulation then moves that heat around the planet, including from the tropics towards the poles. In doing so, the ocean influences temperatures, rainfall and weather patterns across the world.

So when we experience the climate as we know it, we are experiencing a climate system in which the ocean is already doing an enormous amount of invisible work.

The Carbon Account

Then there is the other account we keep drawing from: carbon.

The ocean absorbs roughly a quarter of the carbon dioxide emitted by human activities.

CO₂ moves between the atmosphere and the ocean, while phytoplankton and marine ecosystems help move and store carbon through biological processes.

Again, we get the benefit. More of our emissions are kept out of the atmosphere.

But the ocean picks up the bill.

When carbon dioxide dissolves into seawater, it changes its chemistry and makes the ocean more acidic. That makes it harder for organisms such as corals, oysters and some plankton to build and maintain shells and skeletons.

The ocean is helping clean up our carbon mess. But the cleanup is changing the ocean itself.

THE CLIMATE BILL

We emit.

The ocean absorbs much of the excess heat and a significant share of our CO₂.

We get the benefit.

Slower atmospheric warming. Carbon kept out of the atmosphere. A more regulated climate.

The ocean carries the cost.

Warmer waters. Marine heatwaves. Acidification. Sea-level rise. Coral bleaching. Ecosystem stress.

That is the irony at the centre of our relationship with the ocean.

It continues to protect us. But that protection is changing the ocean itself.

A warmer ocean means more frequent and intense marine heatwaves, which can trigger coral bleaching, disrupt fisheries and force marine species into new habitats. Thermal expansion of warming seawater, alongside melting land ice, contributes to sea-level rise and growing risks for coastal communities.

At the same time, ocean acidification puts additional pressure on marine organisms and ecosystems.

And none of these consequences stays underwater.

They move through fisheries and food systems. Through coastal livelihoods and economies. Through weather systems and communities. Through the millions of people whose lives are directly connected to the sea - and the billions more who depend on the climate system it helps regulate.

This is why the ocean cannot be reduced to another environmental issue.

Protecting the Ocean Is Really About Dependence

We often talk about protecting the ocean as though we are doing the ocean a favour.

Protect the whales. Save the coral reefs. Keep plastic off beaches. Preserve marine biodiversity.

All of these things matter. But the framing can obscure something much more fundamental:

We need the ocean functioning because we depend on it.

Our weather systems depend on it. Our food systems depend on it. Coastal economies and livelihoods depend on it. The climate conditions that have allowed human societies to develop depend, in part, on the ocean continuing to move heat and carbon through the Earth system.

Protecting the ocean therefore cannot only mean protecting individual species or keeping beaches clean. It also means addressing the source of the pressure by rapidly reducing greenhouse gas emissions and protecting ecosystems such as mangroves, seagrass meadows and salt marshes that contribute to climate regulation and carbon storage.

Because the ocean is not separate from the climate system.

It is the climate system.

And perhaps our mistake has been thinking about nature as something outside us for so long that we have forgotten how profoundly dependent we are on it.

Human progress is often narrated through what we have managed to overcome, control or make unnecessary. But we exist within a web of interconnections and dependencies that no amount of technological or economic progress has erased.

The ocean is one of the biggest of those dependencies.

It was here before us. It has been regulating temperatures, moving heat, cycling carbon and shaping rainfall throughout human civilization. We have never experienced life on a planet where the ocean was not quietly working in the background.

So perhaps it was never mankind versus the ocean.

We have never lived on a planet where the ocean wasn't quietly working for us.

And protecting its ability to keep doing so isn't simply about protecting the ocean.

It is about protecting us.