What heats the oceans?

Direct solar heating or back-radiation from CO2?

If you want to understand what the IPCC says about climate science, you spend a lot of time reading Chapter 9: Ocean, Cryosphere and Sea Level Change. Which I’m sure you do — right? If you really want to understand what drives our climate, you’ll need to single out section 9.2.2. But you already knew that, so let’s get into it.

Here is the summary paragraph on ocean heat content and transport. I’m going to break it into single sentences in bold with comments:

Ocean warming — that is, increasing ocean heat content (OHC) — is an important aspect of energy on Earth: SROCC (Bindoff et al., 2019) reported that there is high confidence that ocean warming during 1971–2010 dominated the increase in the Earth’s energy inventory, which is confirmed by the Box 7.2 assessment that the ocean has stored 91% of the total energy gained from 1971 to 2018.

This surprises no one. Temperatures have been going up for 200 years, mostly driven by the PDO and the AMO, not CO2:

It would be strange if 1971–2010 showed a decrease in temperature, since 1950–1971 DID show a decrease in temperature that the IPCC failed to mention. As I showed last week, the Atlantic Decadal Oscillation and other ocean oscillations ensure that temperatures don’t march linearly up or down.

As reported in Sections 2.3.3.1, 3.5.1.3 and 7.2.2.2, Box 7.2 and Cross-Chapter Box 9.1, confidence in the assessment of global OHC change since 1971 is strengthened compared to previous reports, and extended backward to include likely warming since 1871.

Again, this makes sense, though data quality is generally poor, and the 1871 number is laughably arbitrary. Before 2004, all ocean-temperature data is essentially worthless. Back in 1871 sailors threw thermometers off the sides of ships and wrote down temperatures in a log book when they had time. Once in a while, they even threw it on the shady side, not the sunny side of the ship. The technical term for this is “grasping at straws.”

Since 2004, we have better data from the Argo and Triton floats that show a slow, gradual warming. This chart, from Woods Hole, is based on Argo data and is very politically motivated ...

This graph has the data, but the colors are obviously designed for the news cycle. The blue on the upper left is the so-called “pause,” because there was no El Nino then, and that threw the computer models off. This gorgeous bit of Rothko-inspired science shows the surface warming about 0.2 degrees C since 2004, with a high at the 2016 El Nino and some El-Nina cooling over the last three years. It also shows how sluggish the deep ocean is in changing temperature.

At 1,800 meters, even though the graph goes from light blue to golden, the temperature hardly budges at all, it’s well within the error range of the instrument, which is at least 0.4 degrees plus/minus. So all the color in this chart above 200 meters is misleading at best, from 200–400 meters is dishonest, and below 400 meters is meaningless, bordering on fraudulent. The Woods Hole people know this. It’s designed to show a dramatic “transition” from dark blue to dark red in the mixed layer of the ocean that represents a range of 0.3 degrees, which is well within the margin of error of measurement. The data do not show anything dramatic, but the public only sees colors, and journalists don’t understand the visual display of quantitative information, so this kind of chart is money in the bank for fundraisers. Feynman called this “Cargo cult science.”

The average temperature of the oceans is between 3 and 8 degrees C (no one knows exactly - not enough data). Whatever the number is, moving it up 0.1 degree C would take a huge amount of energy — more than many many nuclear explosions — that only direct heating by incoming shortwave radiation from the sun can provide. No amount of downwelling infrared radiation from water vapor or H2O can heat the oceans significantly, as we’ll learn below.

Overall, the entire ocean has gained about 40 zettajoules of heat energy in the last 20 years (all measurements before 2005 are worthless), and there are error bars around that number that get bigger the deeper you measure.

Wait. 40 zettajoules! That sounds like a lot of zettajoules!

Is it? The oceans contain at least 1,000,000 zettajoules of energy (probably much more), so the oceans have warmed about 40/1,000,000 = 0.00004 percent.

Wait. 0.00004 percent in 20 years? That’s negligible. That’s a rounding error. At this rate, it would take tens of thousands of years to warm one percent.

Keep that in mind as you read how dramatically the oceans are warming. Journalists have no idea what a zettajoule is.

To continue following the IPCC trail, we need to look at section 3.5.1.3, which I’m sure you’re familiar with. Here is the key cookie:

Observed ocean heat content changes are discussed in Section 2.3.3.1, where it is reported that it is virtually certain that the global upper ocean (0–700 m) and very likely that the global intermediate ocean (700–2000 m) warmed substantially from 1971 to the present.

Starting in 1971 gives them an excuse to say the warming has been rising as CO2 has been rising, but the data from 1971 to 2005 are worthless — you can choose any trend you like from that period and substantiate it using “evidence.” As we have seen, the global ocean has warmed a microscopic amount since 2005. It almost certainly warmed the same amount from 1871 to 1920, but we don’t have the data to show that.

Most of this section is based on simulations, but one of their claims is:

Since AR5, the attribution of ocean heat content increases to anthropogenic forcing has been further supported by more detection and attribution studies. These studies have shown that contributions from natural forcing alone cannot explain the observed changes in ocean heat content in either the upper or intermediate ocean layers, and a response to anthropogenic forcing is clearly detectable in ocean heat content (Gleckler et al., 2016; Bilbao et al., 2019; Tokarska et al., 2019).

The dog that didn’t bark

I want readers to understand that this is impossible. No amount of CO2 in the atmosphere can have much influence on ocean temperatures, because downwelling infrared radiation can’t penetrate the ocean skin layer (Singer 2006). Even the IPCC knows this, but in chapter 9, they don’t mention that directly, you have to follow the reference papers to see it.

Shortwave radiation coming from the sun has far more energy than reflected longwave radiation coming back down. The shortwave radiation has enough energy to penetrate the water, which you know from snorkeling as the water in the first ten meters really warms up. On the other hand, the longwave radiation reflected back down doesn’t generally go past 2 microns, where it mostly powers evaporation, which actually cools the water below. Longwave radiation can mix a bit of heat down into the top layer if it heats the atmosphere above the ocean, but that effect is dwarfed by both the evaporation effect and by the shortwave energy penetrating the water.

Jim Steele explains:

This is what the IPCC has decided not to understand. The scientists know it, but the “lead authors” decide what goes into the publications. The report shows how the oceans have warmed and don’t explain that this has to be a solar trend, not an atmospheric trend. Read chapter 9 carefully and you’ll see that it’s what they don’t say that is important.

Summary

Shortwave energy from the sun penetrates and heats the oceans down to depths of 350 meters, where the warm water gets mixed in and can heat the oceans directly. Downwelling infrared radiation heats the atmosphere above the oceans but doesn’t penetrate beyond a few microns. Sunlight heats the oceans. The greenhouse effect does not.