Nature’s Thermometer

One of the most common designs for a thermometer works by measuring the volume of a fluid — one which expands when it heats and shrinks when it cools. The classic example of such a “thermometric liquid” is mercury, a liquid metal. Usually the fluid is enclosed in a container (often, a glass tube) so that when it expands it climbs to a greater height. By the height of the fluid, we can deduce the temperature.

Nature has provided us with a vast quantity of a liquid which expands when it heats and shrinks when it cools: water. Nature has also placed most of this tremendous volume of water into a container we call the ocean basins around the globe. If it heats up, it expands and the level of the water rises; if it cools down, it contracts and the level lowers. We refer to that level as sea level.

Other things can affect sea level, the most important being how much water is in the oceans. A tremendous amount of rainfall can move water from oceans to land, enough to make a noticeable change in sea level. But eventually that water makes its way back to the sea, so any consequent rise or fall is only temporaray. The water from melting of land-based ice also makes its way to the sea and raises sea level, but it takes heat to melt ice so that is yet another indicator of warming. On the whole, the height of the sea surface is an imperfect, but genuine, thermometer for gauging Earth’s temperature.

And what, you may wonder, does the ocean-thermometer tell us about the last few decades? It says this (sea level data based on satellite measurements, from the Univeristy of Colorado):


According to the oceanic thermometer, Earth has been getting hotter. Rather steadily, in fact. There is an annual cycle — highest in October, lowest in May — but we can remove that with a variety of mathematical methods:


No doubt about it — the sea is rising, rapidly, and it has continued to do so with only the occasional, very temporary, stutter.

Which raises an interesting question. I’d like to address this question to senator Ted Cruz (R-TX): you’ve said repeatedly, loudly, insistently, that there has been no warming for 18 years. If that’s true, then do tell us, senator Cruz, why has the sea kept rising rapidly?

I don’t expect senator Cruz to answer. Ever.

26 responses to “Nature’s Thermometer

  1. I would expect an answer along the lines of, “it’s just two inches”.

    [Response: To which I would reply: “Senator, you didn’t answer the question. Please answer the question.”]

    Off topic, any thoughts on when we can first expect someone to claim that there has been no warming since 2015?

  2. Better than even chance we won’t hear no warming since 2015. It will take at least until 2016 until the no warming since 2016 meme gets started.

    Who am I kidding? As soon as we get 5 or 6 months where the temperature is less than last year, we can expect the no warming since talk to start.

    • Perhaps Eli can link to a skeptic blog from January 1999 that claims no warming since 1998….

      • There is a progression. In 2000, the mantra was there is no global warming and “The 1998 temperature surge is attributable to an unusually large Southern Oscillation (El Niño), not to an overall warming trend.”

        By 2005 we were starting to get “the average global temperature had declined since 1998”.

        I have not seen it earlier than that. Bob Carter led the pack on that meme, primarily by basing his claim on a comparison of maximum temperatures rather than the actual trend line.

        Deniers are more desperate now adays, so I expect “no warming since 2015” (or possibly 2016) to kick in within three to five years, rather than the seven it took for 1998.

      • I believe those claims use the NASA satellite data, which measures the troposphere, rather than the surface. Given the heat capacities, and the forcing, one would expect the troposphere to warm, but it doesn’t seem to track the surface as much as theorized. I suspect the lapse rate feedback needs to be focused on. Either that or there’s something wrong with the data sets.

        An additional item for your consideration: sea water properties can lead to a volume increase as energy migrates into a deeper and higher pressure environment. Thus it’s possible to visualize a mechanism whereby energy moves from say 150 meters to 3000 meters below sea level, and the overall volume increases a teensy bit.

        This is useful merely as a mental exercise, and to remind you that sea water does have wonderfully well designed properties. I don’t believe in supernatural gods, but those molecules sure look like just what the doctor ordered to keep things working.

      • Not my area of expertise at all, but to the best of my knowledge it is NOT AT ALL easy “to visualize a mechanism whereby energy moves from say 150 meters to 3000 meters below sea level” on any time scale under millennia.

        Perhaps someone knowledgeable can comment.

      • JGNFLD,

        The thermohaline ocean circulation (and other currents) take large amounts of heat from the surface to deep water. Changes in the currents will change the energy exchanged. A change in the saltiness of the surface water could lead to an increase in the temperature of the sinking cold water. The volume of water is so great that a change of .01 or .02 C would lead to substantial changes in energy at depth.

      • If you know anything about the history of the Internet, you’d know that “blog” was a new thing back in 1999. LiveJournal & were only established in that year. But maybe there’s something on Geocities? :-)

        While climate change denial has been around since the 80s, it REALLY only took root after Gore’s An Inconvenient Truth and truly calcified throughout the right wing upon the election of Barack Obama.

    • Meridional overturning circulation is on the order of ~1000 years with the oldest water being found in the North Pacific at 1400 years.

      The highest vertical velocities observed in North Atlantic Deepwater formation (the beginning of the MOC) are <.1 cms^-1, thus are very difficult to resolve. Radiocarbon studies date deepwater formation sites to 200-300 years old since the water started downwelling.

      Depending on the time of the year, mixed layer depth can be below 150 meters making it impossible to move any water mass below those depths.

      Oceanic horizontal scales are far vaster than vertical scales, indeed a lot of GFD actually neglects vertical motion and only looks at horizontal gradients i.e. Thermal Wind.

      • Thanks…that was my for-dummies level of understanding. Water at depths of over 1000 to 2000 meters and greater (the aforementioned 3000 meters) is decoupled from the surface by quite significant periods of time.

  3. David B. Benson

    As a freshman in the CalTech free physics lab I devised a mercury in paraffin thermometer which went down when the temperature went up.

  4. It should be pointed out that water dosnt
    always exhibit thermal expansion due to
    temp rise. It can shrink as well.
    Depends on starting temp.

    [Response: It should be pointed out that at the relevant temperatures, seawater expands when heated.]

    All in all i think sea level change is a great indication of temp change in biosphere.

    Something is going on and its in humanities interest to find out what. As
    quick as possible.
    Some top notch science has given us some damn good ideas.

    [Response: It should be pointed out that we already “found out what.” Ted Cruz just doesn’t want to believe it.]

    I was so heartened by the Montreal Protocol. Things can move fast.

  5. “If that’s true, then do tell us, senator Cruz, why has the sea kept rising rapidly?”


    Senator Cruz: Well, I’m not a scientist, but what about all the droughts we’ve been hearing about? Particularly in California, and probably other places, they have been pumping a lot of ground water out that should raise the oceans a bit. I don’t think anyone really knows how much sea level rise that would generate.
    Well, maybe not. I’m sure whatever Cruz would say you could show he was wrong, but he’ll never talk to you.

  6. In this particular case the senator will seriously doubt the validity of satellite measurements and claim that the data gets distorted/modeled/massaged etc to get the dubious results out.. ;).. Which naturally cannot be the case with satellite based temperature measurements of troposphere which – with all the fits and adjustments and corrections needed – apparently is the denier gold standard…

    Regarding the pause, deniers will be pointing out that apart from short periods of rapid increase the temperature has been essentially flat for 30+ years.. So they will have no problem in stretching their logic to whatever fantasy needed.. ;)..

  7. According to UK Met Office, there is a good chance 2016 will be hotter than 2015.

    So expect a different meme

  8. Playing devil’s advocate, I reply that once the global average temperature reaches a value that causes melting of land ice and warming of oceans, then melting of land ice and warming of oceans will continue each year without further warming of the atmosphere, and global average sea level will continue to rise. And this has been happening since the planet began warming after the last ice age. So increasing sea level by itself can’t prove the global average temperature is rising.

    [Response: If (big “if”) the surface temperature remained constant but heat hadn’t yet penetrated into the oceans, the *rate* of sea level rise would slow. But it hasn’t.

    And of course, if seawater keeps expanding, it’s because it’s still absorbing heat. Perhaps senator Cruz doesn’t include the oceans as part of “Earth.”]

    • No, it has not “been happening since the planet began warming after the last ice age.” The planet has been cooling for the last 6,000 years, and only began heating again with the Industrial Revolution.

      • “The planet has been cooling for the last 6,000 years,”

        So in GOP terms, that’s practically since the dawn of times, right?

    • For the 4-5000 years prior to the Industrial Revolution the global ocean volume was static. This is consistent with the long-term global cooling over that period. So your devil’s advocate approach doesn’t hold water (pun intended).

  9. Well that’s easy. It must be due to The ice sheets melting…no wait

  10. moefamilyannville

    Cruz will also point to the rapidly depleting underground aquifers, the mass loss from which has been measured by the GRACE mission. The key data in my mind is the ocean heat content as linked above by David Lewis, especially the three-month averages which extend from 2005 to the present. The three-month data is based entirely on the relatively new ARGO float measurements, the most accurate ocean measurement system. It is the ocean heat content series that is used to calculate the TOA imbalance – and the imbalance is alive and well. No pause whatsoever.

  11. Obviously it’s inertia! That warmists never know the most basic things of physics.

  12. I expect Ted Cruz would answer, “Look over there! Obama is doing something bad!”

  13. The data is fraudulent.
    Even if the data is real, it’s only a few inches, so it’s not significant.
    Even if it is real and significant, it’s caused by draining lakes.
    Even if it is real, significant, and caused by warming, it is a hangover from warming that happened in the past.
    Even if it is real, significant, and caused by current warming, the warming is not our fault – it’s undersea volcanoes, or the sun getting hotter.
    Even if it is real, significant, and caused by current warming from human activity, doing anything about it would be too costly.
    Even if it is real, significant, caused by current warming, and we could afford to do something about it, we should wait for China and India to do something first.
    And if all China and India are doing something, then it won’t make much difference what we do anyway.