Ocean acidification

Story hook

January 2024. A marine scientist named Derek Manzello, head of NOAA's Coral Reef Watch programme, opens a press conference with sentences nobody in his profession ever expected to say in their lifetime: "We are witnessing the fourth global coral bleaching event in recorded history — and it may be the worst." By April 2024, the declaration is official. By December 2024, 77% of the world's coral reef area has been exposed to bleaching- level heat stress in just 18 months — surpassing the 2014-17 event that was supposed to be unimaginable.

The Great Barrier Reef — Australia's $6 billion tourism asset and the world's largest single living structure visible from space — has experienced 5 mass bleaching events in 8 years (2016, 2017, 2020, 2022, 2024). 93% of its corals show signs of stress. Marine biologists who spent careers studying the reef are openly weeping at conferences.

While the world above water debates +1.5°C vs +2°C, the ocean has already done a quiet, parallel violence — its pH has dropped by 0.1 since the Industrial Revolution. That sounds small. On a logarithmic scale, it represents a 30% increase in acidity — the fastest ocean chemistry change in 50 million years. Coral reefs, which took 240 million years to evolve their calcium-carbonate skeletons, may be functionally extinct by 2050 if current trajectories continue. We are, in real time, dissolving the ocean.

Why this matters for UPSC

Syllabus location: GS-I/III — Environment + World Geography. Asked 2-3 times in Prelims over the last decade. Mains 2018 (ocean acidification), 2022 (coral reefs). Topic rising in salience — every COP, every IPCC report leans heavier on ocean-climate coupling.