A robust feature of global warming is that the surface of the land warms more than the   surface of the oceans. We call this the land/ocean temperature contrast.

The reason is partly because the oceans are slow to warm up compared to land,   but that's not the whole story.

If we were to warm earth's oceans by 1℃ and then stop (in our real world "experiment" we haven't stopped yet), the land would warm by about 1.5℃ and then stay warmer than the oceans, even after the ocean has 'caught up' to the land. The land and ocean surface temperatures have a similar relationship in the warming and cooling of year-to-year variability.