/. That graph shows an estimate of a total of about 500 ZJ added to the the upper 2 km of the oceans since 1955. Aside: Actually, the first 50 years of the graph are nothing but guesses. OHC is estimated by models, informed by temperature measurements, made by Argo floats. The first Argo float was deployed in 2000. They didn't reach 3000 units (i.e., one float per 120,000 km²) until 2007. So the part of their graph prior to about 2005 is 100% codswallop. The kindest thing you can say about it is that it's a plausible guess, consistent with (but you can't say based upon!) convenience samples of sea surface temperatures. It is not data, in any sense. But never mind that, because that graph also has another problem...

/. Does it seem odd to you that, even though all the measurements are of temperature, rather than heat content, THEY NEVER REPORT TEMPERATURES? You should calculate what 500 ZJ means in terms normal people can grok: average water temperature change. If you do that simple exercise, it will be obvious why they do not report it.

/. I know you won't do it, so I'll do it for you. (You're welcome.) Total volume of water in the oceans is 1,338,000,000 cubic-km = 1.338e9 km³. Volume of water in the upper 2000 meters of the oceans: 3.6e8 km² × 0.95 × 2.0 km = 6.84e8 km³ = ≈50% of total ocean volume. The density of seawater is about 1027 kg/m³ = 1.027 tonne/m³ = 1.027 Gt/km³. 6.84e8 km³ of seawater weighs: 1.027 × 6.83e8 = 7.0e8 Gt 1 Gt = 1e12 kg, so the top 2 km of the world's seawater masses: 7.0e8 Gt × (1e12 kg/Gt) = 7.0e20 kg So, let's calculate how much energy it takes to warm that much water by 1°C. Everyone knows 1 cal of energy will raise one gram of fresh water by 1°C, and 1 kcal (1000 cal) warms 1 kg of water by 1°C. 1 cal = 4.184 J, so 4.184e3 J warms 1 kg of pure, fresh water 1°C. Seawater has an 8% lower specific heat of 3.850e3 J / (kg °C). So: It takes 7.0e20 kg × 3.850e3 J/kg = 2.695e24 Joules to raise the average temperature of the top 2 km of the oceans by 1°C. So 500 ZJ (= 5.0e23 J) warms the top 2 km of seawater by an average of (5e23 / 2.695e24) = 0.185 °C, or almost 1/5 of 1°C.

/. That's right, one-fifth of a degree, in about 65 years. Is that supposed to be frightening? And now you know: the reason they don't report it in terms normal people can grok, like water temperature, is to prevent the sniggering when they call it a "crisis."