Explainer: How tropical oceans and El Niños heat the land worldwide

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; the oceans have a much larger heat capacity than land which means lots more energy is required to change their temperature. But that’s not the whole story.
If we were to warm earth’s oceans by \(1^{\circ}\)C and then stop (in our real world “experiment” we haven’t stopped yet), the land would warm by about \(1.5^{\circ}\)C and then stay warmer than the oceans, even after the ocean has ’caught up’ to the land. This is due to the relationship between the surface and the atmosphere above it; the air in the few kilometers above land is much dryer than the air above oceans. This dryer air is more sensitive to change so its temperature increases more than the air above oceans, leading to a land/ocean temperature contrast. The land and ocean surface temperatures have a similar relationship in the warming and cooling of year-to-year variability.

Observed temperature change in the 20C. Note the increased warming over the continents. Figure from (Compo 2008)