How does the ocean affect climate and weather on land?

The ocean influences weather and climate by storing solar radiation, distributing heat and moisture around the globe, and driving weather systems.

This map of sea surface temperature illustrates how heat is distributed across the global ocean.

We live on a blue planet, with oceans and seas covering more than 70 per cent of the Earth’s surface. Oceans feed us, regulate our climate, and generate most of the oxygen we breathe.

They also serve as the foundation for much of the world’s economy, supporting sectors from tourism to fisheries to international shipping.

But despite their importance, oceans are facing unprecedented threats as a result of human activity. Every year, an estimated 8 million tonnes of plastic waste end up in the world’s oceans. At the same time, climate change is damaging coral reefs and other key ecosystems; overfishing is threatening the stability of fish stocks; nutrient pollution is contributing to the creation of dead zones; and nearly 80 per cent of the world’s wastewater is discharged without treatment.

One way that the world’s ocean affects weather and climate is by playing an important role in keeping our planet warm. The majority of radiation from the Sun is absorbed by the ocean, particularly in tropical waters around the equator, where the ocean acts like a massive, heat-retaining solar panel. Land areas also absorb some sunlight, and the atmosphere helps to retain heat that would otherwise quickly radiate into space after sunset.

The ocean doesn’t just store solar radiation — it also helps to distribute heat around the globe. When water molecules are heated, they exchange freely with the air in a process called evaporation. Ocean water is constantly evaporating, increasing the temperature and humidity of the surrounding air to form rain and storms that are then carried by trade winds. In fact, almost all rain that falls on land starts off in the ocean. The tropics are particularly rainy because heat absorption, and thus ocean evaporation, is highest in this area.

Outside of Earth’s equatorial areas, weather patterns are driven largely by ocean currents. Currents are movements of ocean water in a continuous flow, created largely by surface winds but also partly by temperature and salinity gradients, Earth’s rotation, and tides. Major current systems typically flow clockwise in the northern hemisphere and counterclockwise in the southern hemisphere, in circular patterns that often trace the coastlines.

Ocean currents act much like a conveyor belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics. Thus, ocean currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. Without currents in the ocean, regional temperatures would be more extreme — super hot at the equator and frigid toward the poles — and much less of Earth’s land would be habitable.

How climate change relates to oceans

Oceans are a global force of nature that form the foundation of the blue planet on which we live. They cover 71% of our planet’s surface and make up 95% of all the space available to life. They are a life-support system for Earth and a global commons that provide us with free goods and services, from the food we eat to the oxygen we breathe.

The oceans also regulate the global climate; they mediate temperature and drive the weather, determining rainfall, droughts, and floods. They are also the world’s largest store of carbon, where an estimated 83% of the global carbon cycle is circulated through marine waters.

But the interaction between these two natural forces is altering, and the exchange is intensifying. We’re seeing the consequences of this around the world. In the last 200 years, the oceans have absorbed a third of the CO2 produced by human activities and 90% of the extra heat trapped by the rising concentration of greenhouse gases.

The ocean has greatly slowed the rate of climate change. It is a powerful carbon sink. Absorbing a quarter of the carbon dioxide (CO2) released since humans started burning fossil fuels, it has also trapped an estimated 90% of the excess heat created by climate warming gasses.  

But at a cost. The ocean has also warmed, lost oxygen and acidified, currents are changing, and sea levels are rising. To continue along this path not only threatens marine ecosystems, but also the future ability of the ocean to indirectly support life. The ocean is not only a victim of climate change, it is also a vital part of the solution. 

As the climate responds to decades of increasing carbon emissions, the store of energy and heat from the atmosphere builds up in the ocean. If we reach a tipping point, we will likely see more extreme weather events, changing ocean currents, rising sea levels and temperatures, and melting of sea ice and ice sheets—all of which aggravate the negative impacts of overfishing, illegal fishing, pollution, and habitat degradation.

But perhaps of greatest concern is that the basic chemistry of oceans is changing faster than it ever has over the past 65 million years. The continual absorption of CO2 increases acidity levels, and—when combined with the warming of our oceans—more coral reefs are dying off and can no longer offer a healthy ocean habitat for the species that rely on them for food and protection. Scientists estimate if the current rates of temperature increase continue, the oceans will become too warm for coral reefs by 2050.

But even though the challenge of addressing climate change seems immense, solutions are possible to secure a living ocean for a healthy global climate.

We’re off to a good start: more than 100 countries responsible for 90% of global emissions have already made national climate commitments to slash their carbon pollution. World leaders gathered in Paris in 2015 to work together in drafting next steps to act responsibly on climate change. By taking this head-on, we can ensure the security and resilience of the most vulnerable people, places, and wildlife. WWF has and will continue to actively participate in these climate negotiations, urging leaders, businesses, and communities to take the necessary steps to save our planet.

Today, governments at COP26 look to the water, ocean and coastal seas for climate solutions. A healthy ocean can play a key role in reducing CO2 emissions and limiting global warming to 1.5 °C. To do this, governments, NGOs, companies, financial institutions and other non-state actors need to scale up their action in protecting the ocean, its ecosystems, species and resources.  

And there are options available. These include scaling-up action at national levels and including ocean-related measures in their nationally determined contributions (NDCs), strengthening ocean science, increasing the share of climate finance for ocean-based mitigation and adaptation strategies, and expanding marine protected areas. Acting at scale, we can secure a healthy and productive ocean that contributes to a resilient, nature-positive and net-zero future. 

Resources

oceanexplorer.noaa.gov, “How does the ocean affect climate and weather on land? The ocean influences weather and climate by storing solar radiation, distributing heat and moisture around the globe, and driving weather systems.”; unep.org, “Why do oceans and seas matter?”; worldwildlife.org, “How climate change relates to oceans.”; liveocean.com, “A HEALTHY OCEAN IS OUR BEST ALLY AGAINST CLIMATE CHANGE.”;