LESSON 1
What Is Climate Change Doing to the Ocean?
Introduction:
A Changing Ocean
The ocean covers over 70% of our planet—and it’s on the frontlines of climate change. From warming waters to rising sea levels and acidifying seas, Earth’s vast blue engine is undergoing serious shifts.
These changes don’t just affect fish or coral reefs. They ripple outwards—altering weather patterns, shrinking coastlines, threatening food security, and even putting entire island nations at risk. But how does climate change affect the ocean, and why is it happening so quickly?
In this lesson, we’ll dive into the three biggest ways climate change is transforming the ocean: warming, acidification, and rising seas.
1. Ocean Warming: A Heat Trap
The ocean has absorbed over 90% of the excess heat caused by greenhouse gases since the 1970s.
How it happens:
What are the impacts?
Stronger storms & weather disruptions
Warmer ocean temperatures fuel more intense hurricanes and alter global weather patterns.
What are the impacts?
Coral bleaching
Corals expel their symbiotic algae under heat stress, turning white and often dying.
What are the impacts?
Shifting species
Fish and marine animals move toward cooler waters, disrupting ecosystems and affecting fishing industries.
What are the impacts?
Loss of oxygen
Warm water holds less oxygen, which can suffocate marine life in low-oxygen zones.
Did you know?
In 2023, global ocean temperatures hit record highs for months in a row.
2. Ocean Acidification: CO2’s Silent Impact
The ocean doesn’t just absorb heat—it also absorbs carbon dioxide (CO2). About 30% of the CO2 we emit ends up in the sea.
How it happens:
What are the impacts?
Weakened shells and skeletons
Creatures like corals, oysters, and plankton struggle to build and maintain their calcium carbonate structures.
What are the threats?
Threats to food chains
Tiny shelled plankton form the base of many food webs—if they disappear, so do the animals that rely on them.
What are the impacts?
Coral reef breakdown
Acidic waters erode reef-building structures, weakening the habitats of countless species.
Did you know?
Ocean acidity has increased by over 25% since the industrial revolution.
3. Sea-Level Rise: Oceans on the Move
As ice melts and ocean water warms, sea levels rise—slowly but steadily.
How it happens:
What are the impacts?
Flooding of coastal areas
Low-lying cities and towns are more prone to frequent and severe flooding.
What are the impacts?
Saltwater intrusion
Seawater pushes into freshwater aquifers and farmland, making them unusable.
What are the impacts?
Displacement of communities
Island nations and coastal populations may be forced to relocate due to uninhabitable conditions.
What are the impacts?
Loss of land
Erosion eats away at shorelines, and some coastal areas may vanish altogether.
Did you know?
Sea levels have risen about 20 cm (8 inches) since 1900—and the rate is speeding up.
Conclusion
The Ocean Is Sending a Message
The ocean is absorbing the heat, gases, and consequences of human-driven climate change—but it’s reaching its limits. As it warms, acidifies, and rises, marine ecosystems are under pressure, and coastal communities are feeling the effects.
Understanding how climate change is reshaping the ocean helps us prepare, adapt, and most importantly—act. Protecting our ocean means protecting life on Earth.
Key Takeaways:
The ocean is absorbing most of the excess heat caused by climate change.
Carbon dioxide makes the ocean more acidic, which threatens marine life.
Sea levels are rising due to melting ice and warming waters, affecting coastlines and communities.
NEXT LESSON
Overfishing and Bycatch: What Happens When We Take Too Much?
We dive into another human threat to the ocean: what happens when we take more than the ocean can give? Learn how overfishing affects entire ecosystems.
START WITH THE BASICS
