By Andy May
A considerable amount of new information on ocean temperature has been gathered since I last wrote about the subject in 2016 here. In my last post on GHCN and the National Temperature Index, it appeared that ocean temperature trends and the thermal energy distribution in oceans dominate climate change. Land-based weather stations are invaluable for weather prediction, but they tell us very little about climate change. The common definition of climate is an overall change in temperature or precipitation over a period longer than 30 years. But even 30 years is a short timeframe, 100 years might be better. On this timescale, ocean temperature trends are more significant.
Oceans cover 71% of Earth and they contain 99.93% of the thermal energy (“heat”) on the surface. Here we define the Earth’s surface as everything between the sea floor to the top of the atmosphere, ~22km. The land is considered below the surface here, we only include the atmosphere, lakes and rivers as part of the surface. The calculation of surface heat storage, and the necessary references, are detailed in this spreadsheet. As an illustration of the huge impact of the oceans, we should consider that Earth’s oceans contain more thermal energy than exists on the surface and in the atmosphere of Venus, where the temperature is 464°C or 867°F. In fact, Earth’s oceans contain four times more thermal energy than the atmosphere of Venus, yet the oceans have an average temperature of less than 5°C. A spreadsheet containing this calculation and the necessary references can be downloaded here.
We still do not have accurate information on the entire ocean, but we do have a lot more than in 2016, more than half the ocean volume is below 3,000 meters. CSIRO has a nice 2009 dataset of temperature data to 5,500 meters here (Ridgeway, Dunn, & Wilken, 2002). The University of Hamburg has multi-year data to 6500 meters here. The CSIRO NetCDF files opened easily, and we can work with their data, even though it only covers one year. Figure 1 is the average global CSIRO ocean temperature from the surface to 5,500 meters.
Figure 1. CSIRO 2009 global average temperature from the surface to 5,500 meters. Data source: CSIRO.
The temperature drops to a minimum of 1°C at ~4,250 meters and then begins to increase. The distribution of temperature at 4,500 meters is shown in Figure 2.
Figure 2. CSIRO ocean temperature at 4,500 meters. The white areas on the map are shallower than 4,500 meters.
Signs of the thermohaline circulation can be seen in these temperatures. It is still unclear how often the ocean water completely overturns. By overturning, we mean the amount of time required for downwelling surface water to make a completely deep-water circuit and then come back to the surface. This process probably takes at least 1,000 years. It is the major long-term heat exchange process on the surface of the Earth. Thus, when the Earth is receiving more thermal energy from the Sun, or CO2 or whatever is causing warming, it takes a thousand years or longer for it to circulate through the oceans. Figure 3 is a map showing the paths the water takes through the deep ocean.
Figure 3. The major paths deep water takes as it moves from the surface into the deep ocean and then emerges a thousand or more years later. Notice Antarctica is in the center of the map. This is because all the oceans only meet in the Southern Ocean, which surrounds Antarctica. Source: By Avsa – Wikimedia, CC BY-SA 3.0.
As we can see in Figure 3, surface water dives into the deep ocean in the North Atlantic and in the Southern Ocean. It then begins to travel around the world, through all the oceans. It upwells mostly in the in the Indian Ocean, Southern Ocean, and in the Pacific. Because deep water moves out of the Atlantic, but mostly upwells in the other oceans, the Atlantic has a slightly lower sea level than the other oceans. Also see (Reid, 1961). Upwelling deep water is more widespread than downwelling. This NASA web page contains a good discussion and animation of the thermohaline circulation.
Figure 2 shows some mixed temperatures in the Southern Atlantic, next to South American and Southern Africa, this suggests some upwelling might be taking place there. But most upwelling appears to be in the Pacific, Southern, and Indian Oceans.
Discussion and Error
Unfortunately, good data on ocean temperature only goes back to 2004. The data we have suggests that the oceans are warming at a rate of 0.4°C per century. However, the ocean cycle-time is over 1,000 years and the record is only 15 years, so this is very speculative. However, if the oceans are truly only warming at a rate of 0.4°C per century, it seems very unlikely that the speculation about rapid and dangerous warming of the atmosphere is anything to worry about.
The Jamstec (Hosoda, Ohira, & Nakamura, 2008) grid, which we’ve used for the shallower (< 2,000 m) portion of our analysis provides us with an estimate of error. It is an estimate of spatial error, which can also be called gridding error. In other words, do we have enough data to make the map accurately? Figure 4 is a map of this error by year and depth.
Figure 4. Jamstec gridding error in degrees C. Data source: Jamstec.
As we can see in Figure 4, the error in 2001 was quite high until a depth of 1400 meters or so was reached. By 2004, depths below 1,000 meters were OK. As Figure 1 shows, depths shallower than 1,000 meters are highly variable and high errors are expected. These shallower waters interact with surface weather, especially in the so-called “mixed layer.” The mixed layer is a shallow zone where turbulence has caused a near constant temperature from the top to the bottom of the layer. The thickness of the mixed layer varies by season and area, but averages about 60 meters. The mixed layer temperature reflects, in a complex fashion, the surface temperature of the previous few weeks.
In our view, the attempts to deduce the magnitude and rate of atmospheric warming using only sea-surface and atmospheric temperature measurements is foolish and doomed to fail. The true “control knob” of long-term temperature change is the oceans. They regulate the surface temperatures through their enormous heat capacity. The mixed layer alone has over 22 times the heat capacity of the whole atmosphere to 22 km. The regulation of atmospheric temperatures by the oceans also gives us a lot of time to determine if global warming is truly a threat. Currently, we only have about fifteen years of ocean temperature data, but in fifteen more years we will have data over a “climatic” period. If the ocean warming trend in 2035 is still less than one degree per century, we have very little to worry about.
I used R to do the calculations plotted in the figures, but Excel to make the graphs. If you want to check the details of my calculations, you can download my CSIRO R source code here.
None of this is in my new book Politics and Climate Change: A History but buy it anyway.
You can download the bibliography here.
It looks like some people think that because the time constants of the deep ocean are very, very long, they dominate the climate change time lags. I have carried several simulations over shorter time periods from 5 to 20 years. In these simulations, I have used the time constant of about 1 month for the land and about 3 months for the ocean. The time responses of these simulations are very good. Process dynamics used to be my speciality. I know that these time constant dominate in the so-called climate change. If there were long time constant prevailing these changes, we could not observe so quick changes in the global temperature.
This has been my argument for time eternal. ( the bias is from my dad who from my first memory would always talk about how the tropics gave the weather.. joe Bidens dad may have told him what he did when little Joey saw what he saw, my dad would always talk to me about the meaning of tropical cyclones in the overall pattern) Oceans run the shooting match. Its increase in WV not co2 that is causing the warming as can be seen where the greatest warming is taking place and when, in colder, drier areas or in the case of the US in night time lows due to higher wet bulbs. In addition warming oceans outsource co2 which may be the reason for much of the increase until such time an equilibrium is reached. Now is co2 causing the oceans to warm by not allowing the air above to cool, Doubtful given the distribution of warming away from the equator and mainly over polar or dry areas. So what is causing the warming, I have. 2 ideas on that. 1) hydrothermal warm vents, which we know precious little about and in fact when one considers the amount of water in the southern hemisphere and the depths how can we have knowledge of that, But another aspect that I am sure the skeptics on my ideas out there will love to hammer so have at it: A rogue wave type intersection of multi century imperceptible cycles, that are intersecting now. Mariners are acquainted with rogue waves, when an event or set of events many miles and days away can intersect producing, seemingly out of nowhere, a giant wave. While we are acquainted with single event caused monster waves ( example the so called perfect storm had a giant wave come into Nassau from the northeast on a clear day with no wind, putting the city under 3 feet of water or a tsunami caused wave, these other waves may not be seen as the causes can be so far away) . Well think of the warming now. Suppose there are large scale multi century cycles at work here, the action and reaction of other lesser time scale events. Perhaps that is a cause. In any case the shooting match is in the oceans. Until such time they can start to cool, the solar min lovers will have to take a back seat. in fact. the reduction of easterlies due to lower incoming radiation from solar mins may make weak to moderate el ninos. more prominent releasing even more heat. But it was heartening to see this as that is where the shooting match is and the warmer the ocean, the greater the input. Peace out
I have carried temperature simulation from 2001 to the end of 2019. The major driver is shortwave radiation change +1.68 W/m2. Compare this to the RF of CO2 1.6 W/m2 from 1750 to 2011! The mean absolute error of my model is 0.075°C in respect to UAH and 0.082°C in respect to GISTEMP. The rapid temperature changes like ENSO effects are in place. This is would not be possible without pretty accurate time constants.
The earths oceans extend far below the sea bed. They extend into the mantle, until they reach the point where they are turned to high pressure steam. Rhis steam peessure is what hold the oceans in place.
Otherwise, without internal heat, all the water on earth would have long ago dissapeared into the rocks. This can clearly been seen by examining how the water table behaves under the surface.
“The data we have suggests that the oceans are warming at a rate of 0.4°C per century”
I have looked at the data for the past 40 years, which I think is a reasonable time period. See:
https://woodfortrees.org/plot/hadsst3gl/from:1979/to:2021/trend/plot/uah6/from:1979/to:2021/trend/plot/hadsst3nh/from:1979/to:2021/trend/plot/hadsst3sh/from:1979/to:2021/trend
I am getting it at ca. 0.8 K/ 40 = 2K/century (NH)
I am getting it at ca. 0.3K/ 40 = 0.7K /century (SH)
Average, if indeed you can take an average from such data – since they are obviously from different populations – is then 1.3K/century.
Obviously, the warming of the oceans is causing the warming of the air. Not the other way around. If it were the CO2 causing a drop in cooling, the rate in the SH should be the same as in the NH, since CO2 is a diffused more or less equal in the atmosphere.
Note that in the arctic area itself, there is even more variation in the data, showing much more than 2K warming per century.
Inter alia, the warming in the arctic is probably the main cause for the continuing increase in CO2 in the atmosphere as the sink area, where the reaction: CO2 + 2H2O + cold => HCO3- + H3O+ takes place,
has become much smaller.
One effect is not often discussed – the “coke bottle effect”…open a bottle of cold pop, look down, and see a few bubbles of CO2. Open that same bottle, when it has been sitting outside for a while, and watch the coke boil out, and rather swiftly, as the dissolved gas comes out of solution. During the last 5 decades or so, the sun has been more consistently warmer, than in the early 1900s. So there appears to be at least some correlation between this warmth, and increased CO2.
This certainly has been ignored now, for decades, as a contribution to atmospheric CO2….
Joe
That is how life came into being….
CO3 2- + H2O => HCO3- + OH-
HCO3- + heat = > CO2 (g) + OH –
Rise of CO2 in the atmosphere follows heat. It does not cause heat. At least not much.
One reason for the increased heating from the sun is due to the removal of S02 emissions from coal fired power plants required by the 1980 Clean Air Act Amendments. Couldn’t believe some suggesting that we start emitting SO2 again to slow down warming.
There could be others. What about oil contamination on water?