The evolution of industrial-era warming across the continents and oceans provides a context for future climate changeand is important for determining climate sensitivity and the processes that control regional warming. Here we use postad1500 palaeoclimate records to show that sustained industrial-era warming of the tropical oceans first developed duringthe mid-nineteenth century and was nearly synchronous with Northern Hemisphere continental warming. The earlyonset of sustained, significant warming in palaeoclimate records and model simulations suggests that greenhouse forcingof industrial-era warming commenced as early as the mid-nineteenth century and included an enhanced equatorialocean response mechanism. The development of Southern Hemisphere warming is delayed in reconstructions, but thisapparent delay is not reproduced in climate simulations. Our findings imply that instrumental records are too shortto comprehensively assess anthropogenic climate change and that, in some regions, about 180 years of industrial-erawarming has already caused surface temperatures to emerge above pre-industrial values, even when taking naturalvariability into account.