Toward A New Climate Paradigm – Watts Up With That?

Guest Post by Willis Eschenbach

What got me into investigating climate science a quarter-century ago? The astounding stability of the Earth’s global surface mean temperature (GMST). For example, since the year 1900, a century and a quarter, the Earth’s temperature has gone up by 0.46 ± 0.07 percent.

I’ll say it again. In a century and a quarter the Earth has warmed by less than half a percent

The Earth’s climate system is a curious thing. It is a giant solar-driven heat engine. A heat engine is a device that turns heat into mechanical motion. In the case of the climate, the mechanical motion is the endless, ceaseless motion of the ocean and the atmosphere. Like all heat engines, the climate heat engine is heated at the hot end, and then the heat is transferred to the cold end and leaves the engine.

So I started out to discover why the temperature is so stable. Yes, I know that from our tiny human perspective it seems unstable, but for a heat engine, the temperature varying by less than half a percent over a century and a quarter is very stable. And here’s what I found out.

Like all flow systems far from equilibrium, the climate is ruled by the Constructal Law, one of the most under-appreciated discoveries of modern thermodynamics. The Constructal Law governs the evolution of flow systems.

And as the Constructal Law requires, the climate heat engine is constantly evolving to maximize the flow. The Constructal Law is a sort of Ten Commandments for anything that flows—rivers, blood, traffic, and, yes, the climate itself. The basic idea?

Everything that moves is constantly evolving and morphing to make movement easier. Life, it turns out, is just one big game of “How can I get from here to there with the least amount of fuss?” The Constructal Law is why river deltas look like the branches of a tree, which in turn look like the alveoli in our lungs. They are all controlled by the Constructal Law.

From a Constructal Law point of view, the climate is not a fragile, teetering system on the verge of collapse, but a gigantic, heat-hauling Rube Goldberg machine.

The sun pours energy onto the tropics, the poles are the cold end of the heat engine, and the atmosphere and oceans get busy shuttling all that heat from the equator towards the poles, where it escapes to space far more easily than at the tropics. Here’s a map of what areas lose or gain energy by this flow.

Figure 1. Average of flow of heat which is constantly being exported from the tropics to the poles, March 2000 to February 2024.

According to Bejan, the climate doesn’t maximize temperature, or CO₂, or even the number of climate conferences in Paris.

No, what it’s really maximizing—relentlessly, remorselessly, every minute of every day—is the flow of heat from where it’s hot to where it’s not.

Picture the earth as a planetary HVAC system, always rearranging its ductwork to get the job done faster. The Hadley cells, the jet streams, the ocean currents—none of these are accidents or the result of a committee meeting. They’re the system’s way of morphing itself to maximize that poleward heat flow. The boundaries between the warm and cold zones, the size of the tropical belt, the speed of the trade winds—Bejan’s math predicts them all and the numbers line up with the real world.

And here’s the kicker: when you let the system optimize for maximum heat transport, a bunch of other things fall into place. The average surface temperature, the temperature difference between the equator and the poles, the total amount of heat getting shunted north and south—Bejan’s model nails them all, without the need for fudge factors, hand-waving, or appeals to the climate gods.

How do I know that? I know because I created and ran what I believe is the first actual real-world based exemplar of Bejan’s theoretical climate model on my computer and saw how successful it was. The whole process is described in the post below.