I am a climate scientist, a computer modeler studying the things we put in the atmosphere. On first glance, my work seems confined to a realm wholly above and separate from the underwater world. But the ocean and the air are the great conspirators of our climate. The motions of the atmosphere, the rise and fall of air above us, are dictated by the temperature of the sea surface. Much of our weather is shaped by the back-and-forth slosh of water in the tropical oceans.

Some years, around Christmas, the waters of the Eastern equatorial Pacific become abnormally warm. This El Niño, an imaginary visitation from the Christ child, feeds violent tropical thunderstorms above the warm pool of water. The tropical East floods; drought comes to the West. Indonesia and Australia burn.

The atmosphere is listening, and it carries the sea’s messages far afield. The trade winds weaken, barometers measure drops and rises in pressure, and air currents are re-directed. El Niño brings rain to the American Southwest, mild winters to southern Canada, reduces hurricanes in the north Atlantic. The average temperature of the entire planet increases. We, all of us, are at the mercy of the ocean.

Before we existed, and after we are gone, the ocean will continue to whisper to the atmosphere. Weather patterns will change back and forth with the natural oscillations of air and water. But we do exist, and we are treating the atmosphere as a limitless dumping ground. A signal of our handiwork is emerging against this cacophony of noise. Things are changing.

A chart showing where all the extra heat is being absorbed by the Earth. (Credit: Katherine Hayhoe)

Dive into the ocean and there is no immediate impediment to progress. At some point your ears pop. Stray too deep or too long and gases make bubbles that pop in your joints. To dive into land requires mechanical assistance: dirt beneath fingernails, shovels in sweaty hands, a screw turned by internal combustion. Deep in the ocean you may find a wrecked ship, tarnished gold, dissolved clothing threaded through buried skeletons. Deep in the earth we find fossils, the compressed detritus of primeval death. Burning these gives us light and energy and heat. Some of this is deliberate and localized. Some, however, is not.

We find greenhouse gases difficult to understand. Accepting that gas means danger is a sad condition of modernity. But we imagine rancid air that tickles then chokes, yellow clouds on a battlefield in Flanders. We accept that burning is warmth, but that its byproducts may linger and mix without color, odor, or taste seems too strange. Linger they do though. They trap the thermal effluence of the planet and, in so doing, warm the planet.

The warming is not immediate. Delays are built into the system: there are different forms of inertia here. The air warms first, then the land, then surface winds mix the shallow surface layer of the sea and finally the abyssal reaches of the ocean. The heat slowly trickles down to the deep, churned by slow overturning ocean currents. The ocean is slow to warm, but it will receive the message in time.