Earth’s climate has changed many times over the planet’s geological history. The alternation of cold periods—marked by ice sheets reaching even low latitudes—and warm periods—marked by rising temperatures and sea levels—stems from cyclical astronomical movements of the planet and its position relative to the Sun. Evidence of these long-term, periodic shifts (on the order of roughly ten thousand years) is preserved in fossils, landforms, rocks, and ice.

Since the Industrial Era, however, greenhouse gases from human activities have risen steadily, triggering a rapid, profound climate crisis—the greatest emergency the planet faces today. Forecasting weather patterns and how the climate is changing is complex, and managing the resulting impacts is challenging. What is certain, though, is that the single most important element helping to regulate Earth’s climate—and to buffer the effects of human activity—is the Global Ocean.