Meridional warming

Update (7/2): I made a silly mistake with normalising the averages. The text and figures have been updated with the correct results.

In this post I am going to present global temperature data in a different way to highlight how the earth cools by transporting heat from the tropics to the poles. This shows that enhanced CO2 warming is mainly concentrated in northern latitudes. To do this I use the latest monthly Hadcrut4 gridded data from 1900 to 2016 and integrate it over longitude and seasons to form yearly meridional temperature profiles.  Here are the results.

Figure 1. All 117 meridional temperature anomaly profiles from 1990 to 2016. They are coloured blue if the annual global anomalies < -0.2C, Blue,-0.2<grey<0.2, 0.2<yellow<0.4, red > 0.4. Traces are 80% transparent to view them all.

There has essentially been hardly any warming (within measurement errors (0.1C)) less warming  between -50 < lat < 50 than at the poles. Much of the  significant warming is concentrated  at latitudes > 50.

Of course it is  real temperatures that  actually affect our lives rather than temperature ‘anomalies’.  So in order to plot the actual temperatures I have used a standard meridional temperature profile based on long term measurements of our climate – see Scotese (Paleomap Project). Here are the resultant temperature profiles relative to the normal, offset by the measured anomalies over  the last 116 years.

Figure 2. Average temperature profiles from 1900 to 2016 calculated relative to a standard profile. Colour scheme is the same as Figure 1.

One sees on this scale just how tiny any relative increase in temperature really is. In a previous post we saw  how most warming actually occurs in winter, when temperatures fall to -40C in the Arctic and to -50C in the Antarctic. Compared to such extreme temperatures, a relative  increase of just 0.5C is tiny. We can see this by looking at more detail in the Arctic region.

Figure 3. Detailed look at changes in absolute temperatures at high latitudes.

The use of anomalies to present global temperatures is confusing because it assumes that all measurement locations are warming by the same amount globally. Instead warming is concentrated towards the Arctic, reflected an increase in heat transport away from the tropics. An increase of 1C at the equator would be far more serious than a 1C rise in the Arctic winter from -50C to -49C.

Over the last 500 million years the earth has been through extreme hot house to severe Icehouse climates. This is what the meridional temperature profiles looked like under extreme climates.

Figure 4. Credits: Christopher R. Scotese. Palemap Project 2015

Such changes as we observe in the Hadcrut4 temperature are totally insignificance when compared to these far larger changes in the past. Warming is concentrated in the coldest places on earth because heat transport by the atmosphere and oceans has increased slightly. Sea levels are rising linearly since 1850 at about 1.3 mm/year probably as a result. However, even at this rate it would still take 1000 years to rise by 1-2 meters.

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21 Responses to Meridional warming

  1. Ron Clutz says:

    Thanks for further explanations on this. On fig. 12 it appears that we are presently on curve #6 with a GMT of 15C.

  2. charplum says:

    Clive

    I really like what you are doing here. Based on what you have posed Bugs Bunny might have asked, “What’s all the hubbub, bub?”

    What does a change in global temperature really mean?

    • pete says:

      “What does a change in global temperature really mean?” About $90,000,000,000,000 over the next 80 years transferred into Big-Wind and Big-Solar oligarchs’ pockets and their politician-godfathers.

  3. Ron Clutz says:

    Scotese shows a modern profile with GMT 14.4, rising from preindustrial at 13.8.

    We are still in a severe ice house and warming (thankfully) very slowly.

  4. erl happ says:

    The concept of a global average temperature has no practical utility. Anomalies in respect of the global average ……..so help me……devoid of meaning altogether.

    High latitudes warm in winter….now, that’s worth knowing.

  5. Ron Graf says:

    Clearly the temperature at the poles are less stable. It would be interesting to quantify the factors: ice sheet albedo, exponentially lower blackbody radiation efficiency at lower temps, lower atmospheric heat transport from transpiration. It sheds light on the degree of the rate of meridonal heat transport (via the global conveyor) if important to the poles.

    Clive, do you think that the cooling over the last 50ma has anything to do with continental interference with meridonal ocean currents. Or, is it all CO2, as Hansen and Sato(2012) postulates?

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  7. Pingback: Meridional Warming – Climate Collections

  8. Michel says:

    Why do you write This shows that enhanced CO2 warming is mainly concentrated in northern latitudes.?
    Any other cause of warming would have the same effect of latitudinal distribution..
    And: data availability and quality for the poles is quite poor. The analysis cannot be better than the data.

    • Clive Best says:

      The reason is that the earth cools mainly by moving heat polewards from the tropics to colder regions which then radiate that excess heat (relative to solar) out to space. The main effect of increasing CO2 is to increase this heat transport process. The effect is that most warming occurs in those colder place.

      Data availability in Antarctica is almost non-existent. There are more stations in Arctic regions because of the vicinity of inhabited continents. Having observed that the Arctic is indeed warming the temptation of climate ‘scientists’ has been to infill those areas without direct measurements so as to accentuate the effect. Meanwhile they ignore Africa where coverage is appalling and the southern hemisphere which is not warming because it is dominated by oceans.

  9. Eric Barnes says:

    Awesome Clive. Thanks!

  10. erl happ says:

    Clive, the transport of heat from the equator to the poles is dependent non the oceans and secondly the atmosphere via ‘wind’. As surface pressure falls at the pole and rises at the equator and mid latitudes so the wind heading in a polar direction grows stronger. By far the most dramatic change in pressure occurs at the Antarctic circumpolar trough……a steady decline over the last seventy years. The atmosphere moves in a south easterly direction across both hemispheres and the rate of movement changes over time.

    This is driven not by CO2 change but by the strength of polar cyclone activity that is generated at Jet stream altitudes by big differences in air density….related directly to the ozone content of the air. CO2 is well mixed. Ozone is not.

  11. frankclimate says:

    I reproduced the figure 2 of Scotese with the data of ERA int. and C/W for the warming from 1950…2016:

    Urgent action is needed!! 🙂

  12. Andrew Carey says:

    Does this mean that average global wind speeds should be declining? The logic ( to me ) is that the differential between the tropics and the temperate regions has declined, and so the driving force behind wind on this planet has reduced a little. If the prediction is reasonable, then does the last couple of decades data on global wind speed support the predicted effect?

    • Perhaps, but probably not significant.

      These are surface temperatures, not higher in the troposphere, where kinetic energy is maximal.

      The size of change is small.

      And when considered jet streams, not pole-to-equator gradient, but 35-to-55 degrees gradient which is less.

      Weakening is part of the Francis hypothesis, of course, but there is a wide variety of equally valid wave patterns for any given gradient.

  13. Ron Graf says:

    I notice that there is more variability at -70 latitude than -80 or -90, where it also warmer on average. What is the physics that is causing -70 to be the global minimum? Is it the high albedo of fresh seasonal sea ice causing both variability and lower temp?

    • My first guess would be simply the sparsity of stations around Antarctica.

      Waves tend to mean warmer in one area, but cooler in another.
      These waves change, not just from synoptic ‘weather’, but also in the statistical averages from year-to-year, decade-to-decade, and century-to-century.

      Were there a hundred stations rather than just a few stations at 70S, I suspect there would not be as much variability in the latitudinal band average there.

    • erl happ says:

      Variability at 60-70° south latitude is tied to stratospheric phenomena that determine the strength of polar cyclone activity. It is here that surface pressure attains a planetary minimum but highly variable on all time scales. The surface air converges in polar cyclones.

  14. Steven Mosher says:

    If you want absolute temperatures, just use our land ocean. duh.

    anomalies are only confusing to folks who cant add and subtract

    • what’s to add and suntract, Stevooo? Temp is different on every 2km2 – and changes every 15 minutes INDEPENDENTLY – our planet is a big, big place. Also is different on every 50m altitude; give us all the variations – so ”we can add up and subtract” please?!?!

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