From KlimaNachrichten

By Frank Bosse

Let´s look at the trends in ground temperatures (that is, the data from land and the surface temperatures of the oceans) from 1980 to 2024:

It is noticeable that land masses generally warm up more than oceans, the factor is 2.3 overall. You can also see immediately that the most warming is far in the north. This is the consequence of the “Arctic amplification” of warming. The earth receives most of the sun’s power all year round in the tropics, it radiates most of the heat over the poles. The area involved in this heat transport decreases more and more towards the North Pole and so the higher heat flux also “condenses” and the areas there warm up more strongly on the ground. Antarctica in the south is also a different case due to its height above sea level.

But why do surface land masses warm up so much faster than the oceans?

The simple explanation: “The thermal inertia of water is much greater than that of land” sounds very plausible, but it is very erroneous. Why?

If the SST (surface temperatures of the oceans) are determined, this is done at a water depth of 3-8m. As the name suggests, you only scratch the surface. You find the temperature of a layer of water that is in contact with the atmosphere and is well mixed, hence the name: Mixed Layer. How deep does this layer reach?

You can see that this layer is only about 15-60 m thick in large parts. In the northern hemisphere (“boreal”) summer, it reaches much deeper in the Southern Ocean, in winter it is the other way around in higher latitudes. This is achieved by a lot of wind (“Roaring forties”) in the corresponding seasons. In the large areas of the tropics, the layer remains at about 15-50 m all year round. This is the measured layer when the SST is determined, by far not the entire ocean in its depth. Look at the actual warming rates in Fig. 1: Depending on the location, it is 0.01-0.02 °C per year. The mixed layer of the ocean has a much higher thermal inertia than land areas, but this does not play a role with the low warming rates of 1-2 hundredths of a degree per year. It is about as if you heated a water pot with a volume of 1 litre and another with a volume of 10 litres in a room by 0.5 degrees in 24 hours. Both volumes will end up being half a degree warmer, despite the higher thermal inertia of 10l of water. Water and land areas can also follow the warming caused by climate change without much effort. The global ocean also constantly follows an annual cycle at the surface, which even accounts for about 0.4°C every year.

This is logical applied physics. Unfortunately, not even some climate scientists take this into account today.

A very recent post on X (formerly Twitter) illustrates this:

In the 2nd sentence it says: “Due to the much higher heat capacity of water than that of land, the ocean warms with a lower trend than the land”

It should be noted that Ms. Makiko Sato has a PhD in physics, has done a lot of climate research (now retired) and is co-author of a new paper with James Hansen (also retired, until then head of NASA’s climate division, GISS). One should assume that it is well aware of the causes of the difference in land-ocean warming. She obviously doesn’t know it, otherwise she wouldn’t have published such a, sorry, nonsense.

We now know what it is not. Now let us know what the real cause is!

A true pioneer of climate research and Nobel Prize winner, Syukuro Manabe, made a first and decisive contribution to the solution. In this paper, he found as early as 1991 using an early climate model that land and ocean warm differently due to increasing CO2 content in the atmosphere. However, this remained the case even when a steady state was reached after doubling, an equilibrium. So it could NOT be a question of heat capacity, because nothing changed in the model over time.

Rather, Manabe concluded that it must be the different evaporation rates. There is always enough water available over the ocean to evaporate. This works even better with warmer water, 7% more can be evaporated per degree of warming. The situation is different over land: Especially in dry areas, there is very soon simply no more water to evaporate. This cools by changing the state of matter. Place a bottle of water and a second, which you surround with a textile and soak with water, in the sun with a little wind. You will notice that the wrapped bottle is much cooler than the dry one on the outside. It is evaporation that accomplishes this. If the wrapping has become dry, this bottle will also heat up quickly.

So you can put it another way: The steepness of the warming depends on the drought. The drier it is, the faster it heats up because there is less water available for evaporation. Oceans are zero dry, by definition, they warm the slowest. Now it also becomes clear in Fig.1 why (very dry) desert areas, e.g. in the Middle East, warm up faster than very humid areas, e.g. in India. As a first approximation, the steepness of the warming trend is inversely proportional to soil moisture. If you want to read it in more detail, this article is recommended.

Was that too difficult? If not, you are now ahead of a “top climate author” and graduate physicist. Perhaps it would be better for Sato to first master some elementary basics for understanding the effects of climate change that have been known for over 30 years before she participates in current “groundbreaking studies”? Good question!