Ocean Warming

What is Ocean Warming?

When we burn fossil fuels—like coal, oil, and gas—we release carbon dioxide (CO₂) and other greenhouse gases into the atmosphere. These gases trap heat, warming the Earth. But did you know that over 90% of this excess heat ends up in the ocean?

This is called ocean warming, and it’s happening faster than ever before. According to NASA, the past decade has been the warmest on record for the world’s oceans.

How Ocean Warming Affect the Reefs

Corals are sensitive organisms that thrive within a narrow temperature range. When the ocean gets too warm—even by just 1–2°C—corals become stressed and undergo a process called bleaching.

Bleaching happens when corals expel the colorful algae (zooxanthellae) that live inside their tissues. These algae provide corals with most of their energy through photosynthesis—and also give reefs their vibrant colors.

Without these algae:

  • The coral turns white (hence "bleached")

  • It becomes weak and vulnerable

  • If the stress continues, the coral can die

Bleaching doesn't kill coral instantly, but repeated or long-lasting warming prevents them from recovering.

The Great Barrier Reef

Before

After

Australia’s Great Barrier Reef has experienced three major mass bleaching events—in 2016, 2017, and 2020—due to heat waves linked to climate change. In some areas, up to 50% of corals died.

This isn’t a local problem. Coral bleaching is now reported in reefs across the globe—from the Caribbean to the Indian Ocean.

According to the IPCC (Intergovernmental Panel on Climate Change):

At 1.5°C of global warming, 70–90% of coral reefs could be lost.

At 2°C, that number rises to 99%.