Heating

Earth’s energy imbalance more than doubled in two decades, reaching 1.8 W/m² in 2023. That is twice what climate models predicted.¹

About 89% of the excess heat is stored in the ocean.²

The main cause of the rise is a darker planet: in 2023, planetary albedo hit a record low, mainly because of reduced low-cloud cover.³

Acidification

The ocean has absorbed about a quarter of human CO₂ emissions.⁴

Open ocean surface pH has fallen by 0.017 to 0.027 units per decade since the late 1980s.⁵

By 2020, more than 40% of the surface ocean and up to 60% of the upper 200 m had crossed the ocean acidification planetary boundary.⁶

Lower pH can also reduce the bioavailability of dissolved iron to diatoms and coccolithophores.⁷

Declining marine life

Monitored marine vertebrate populations have declined by 56% on average since 1970.⁸

Oceanic sharks and rays have declined by 71%, driven by fishing pressure.⁹

Satellite data show that net primary production has declined significantly across 48% of the ocean, driven by stronger nutrient limitation.¹⁰