The ocean is more than a backdrop for sunsets and surf — it’s the origin and engine of all life on Earth, responsible for regulating our climate, absorbing heat, circulating currents and producing oxygen.
But human-driven climate change is pushing the ocean past its limits. As waters heat up and currents shift, a delicate balance is starting to wobble — with consequences that reach far beyond the waves.
Here are five ways the ocean keeps our climate in check — and what we can do to help keep these systems running.
1. It soaks up heat. The ocean is Earth’s ultimate climate buffer. Since the 1970s, it has absorbed more than 90 percent of the extra heat trapped by greenhouse gases, along with about a third of all human-driven carbon emissions since the Industrial Revolution. Imagine how much hotter the planet would be if all of that heat were in the atmosphere.
But the ocean can’t keep absorbing unlimited heat. As humans pump more carbon into the atmosphere, ocean temperatures are continuing to rise, straining the systems that have kept Earth’s climate stable. In fact, as waters continue to warm, they’re beginning to actually release carbon dioxide back into the atmosphere — turning this crucial buffer into a potential amplifier of climate change.
Only by cutting emissions now and protecting nature can we begin to ease this pressure and keep the ocean working in our favor.
Further reading: Heal our planet: Protecting nature for climate
© Comstock Images
2. It shapes climate shocks on land. What happens in the ocean shapes how climate change is felt on land. This is because virtually every drop of rain begins in the ocean. The ocean holds about 97 percent of all the water on Earth, making it the primary source for evaporation into the atmosphere. This constant exchange between sea and sky fuels storms, fills rivers and sustains the freshwater systems that all life depends on.
But warming oceans are shifting this ancient rhythm . Hotter seas speed up evaporation, sending more moisture into the atmosphere — which means heavier downpours in some regions and longer dry spells in others. From the Mongolian steppe to the shrublands of southern Africa and the mangrove forests of India , the climate shocks on land often have their roots in record ocean heat.
3. It keeps global temperatures in balance. Ocean currents act like a giant conveyor belt, carrying warm water from the tropics toward the poles and sending colder water back again. This steady circulation evens out temperatures across the globe, making much of the planet habitable. Without it, the equator would be far hotter, the poles even colder, and life as we know it would look very different.
One of the most important currents is the Gulf Stream, which transports warm water from the tropics to the North Atlantic, regulating the climate of Western Europe. But as melting ice sheets pour fresh water into the sea, that delicate balance of heat and salinity is being disrupted — pushing the system toward a critical tipping point .
We know it can happen: Around 13,000 years ago, a shutdown of the Gulf Stream plunged Europe into a sudden ice age. Today, scientists warn that human-caused climate change could trigger a similar collapse within our lifetime .
Further reading: 5 things you didn’t know about sea-level rise
© Levi S. Norton
4. It produces oxygen. The ocean is full of tiny marine plants known as phytoplankton that are responsible for generating about half of the world’s oxygen supply .
This isn’t a new role. Billions of years ago, microscopic organisms in the ocean began releasing oxygen, gradually transforming Earth’s atmosphere into one that could support complex life. Without them, neither humans nor many of the species we know today would exist.
Now, that life-support system is under pressure. Rising ocean temperatures and acidification are threatening species of plankton, which are also the base of the marine food web. Heatwaves can trigger massive die-offs, while excess carbon in the water makes it harder for plankton and other marine life to thrive. If these organisms disappear, the effects on the food web ripple all the way up — through marine ecosystems, into human economies and even into the air we breathe.
Luckily, science shows that healthy and diverse ecosystems are more resilient and tend to recover better from climate stressors like heatwaves and acidification. Through the Blue Nature Alliance , Conservation International and partners have launched an unprecedented effort to double the amount of ocean area under protection — from the glacial waters of Antarctica’s Southern Ocean to the teeming tropical shores of Costa Rica.
5. It locks away carbon in coastal ecosystems Where land meets sea, coastal ecosystems like mangroves, seagrass meadows and tidal marshes act as powerful carbon sinks. They absorb massive amounts of carbon from the atmosphere and lock it away in waterlogged soils, keeping it out of the air and slowing climate change. These “blue carbon ” ecosystems also protect coastlines from storm surges and sea-level rise, support fisheries and sustain livelihoods for local communities.
In Costa Rica — a country whose ocean territory is ten times larger than its landmass — Conservation International is helping develop the world’s first national blueprint for mangrove protection and management.
This “national blue carbon strategy ” is guiding restoration in places like the Gulf of Nicoya, on the country’s Pacific coast. Years ago, huge swaths of mangroves were cleared to make way for sugar plantations and shrimp farms. To bring them back, Conservation International and the local community are digging channels — by hand — to restore the natural flow of tidal water. The idea is that by creating the right ecological conditions, the mangroves will come back on their own. The approach is catching on — Mexico has already taken note .
© Francisco Azofeifa
Community members dig channels by hand to restore the natural flow of water.
In the Gulf of Nicoya, mangroves provide roughly US$40,747 per hectare annually in combined benefits: food, coastal protection and climate regulation. As climate change accelerates, these coastal forests are more important than ever, giving communities a fighting chance.
Want to support work that protects oceans, coastlines and the people who depend on them? Here’s one way .
Further reading:
Will McCarry is the content director at Conservation International. Want to read more stories like this? Sign up for email updates . Also, please consider supporting our critical work .
