Ocean Land Temperature Differential

Since there is a discussion on what "Fixed" lapse rate really means, I thought I would break out this comparison.  In orange is the temperature differential between the southern hemisphere oceans and land mass.  There is less than 50 million kilometers squared of land in the southern hemisphere and nearly 15 million of that is covered with 2000 meters of ice.  The southern hemisphere is water dominate.

In blue is the northern hemisphere oceans and land temperature differential.  There is about 100 million kilometers squared of land in the northern hemisphere and a much small fraction is covered by ice of any depth.  It should be pretty obvious that the two hemispheres respond differently to all forcing.  Assuming that the "Global" temperature will respond uniformly to all forcing would appear to be a fantasy over time period less than thousands of years.

If you would like to estimate how much impact there will be with increased CO2, it would seem to be wise to consider the MAJORITY of the surface of the Earth.

Using CO2, both directly measured at Mauna Loa and estimated based on fossil fuel land use to 1800 AD, this chart indicates that with the exception of the northern hemisphere land, the "sensitivity" to CO2 forcing is approximately 1.6C per doubling using my Redneck CO2 Tracer simple "fit".  That "fit" does not include longer term change in climate.  Since prior to the modern instrumental era it is rumored that there was a little ice age, some portion of that "sensitivity" could be due to a long term "persistent" increase in ocean heat capacity.

The real question should be how much and how long has there been long term persistence since regional paleo indicates that there has been throughout history.  "Globally" the surface temperature may be stable, but mankind lives mainly in the northern hemisphere. 

Sea level rise appears to indicate that there is considerable long term persistence.  Unfortunately, with statistical massaging you can find anything you would like.  Selecting an anomaly baseline that is too short or on an upslope/downslope skews your results to that period.  If you select an anomaly baseline that is too long, you lose most of the information.  When you compare too short with too long you get fruit salad.  This chart uses the full global mean sea level data with an anomaly baseline from 1880 to 2006, the full length of the CMAR data set then it is "normalized" by dividing by the standard deviation for that baseline period.  Using the same procedure on the ERSST data and Hadley Center CRU4 Global data set, this is what you get.  Sea level, SST and Global Mean Temperature Anomaly all indicate that there is long term persistence. 

Of course if I select an different shorter baseline, the results vary considerably.

Here by using the 1955 to present baseline I get a nice hockey stick.  The hockey stick market is cornered, so I doubt that I can make any money trying to scare the little kiddies of the world with this, though it is a great method to use for Cli-Fi fiction.  This post outlines the methods and should provide any links I have missed.

There is a wealth of real science published that deals with the long term ocean driven climate pseudo-cycles which I find much more fascinating and believable than the Cli-fi hockey sticks. To each his own though. 

Adjusting the CO2 Tracer Signal

CO2 is one of the few atmospheric forcing components we have a reasonable handle on.  A doubling of CO2 will produce about 3.7Wm-2 of atmospheric forcing, which based on a temperature 255K degrees (240Wm-2) a temperature increase of approximately 1 C degree.  If you live in an area that has an average temperature of -18C degrees (255K), then you can expect about one degree of warming per doubling of CO2.  Anything more or less requires help in the form of amplifying or dampening feedbacks.

Since zero C is the freezing point of water, that other greenhouse gas, if you live in an area that has an average annual temperature of zero C can can expect a little bit more warming due to CO2.  As temperature and water vapor increase, the impact of CO2 decreases.  This is the reason for the polar amplification often mentioned and the less than expected warming over the oceans and in the tropics.  If you don't want to take my word for it, you can find a number of sources, but that is not the main point of this post.

The Carbon Dioxide Information Analysis Center (CDIAC) has a ton of information on CO2.  There have been direct measurements since 1959 at Mauna Loa in Hawaii, but longer term CO2 measurements are generally dismissed for some reason or another.  Since Fossil fuel use is the culprit that is supposed to cause the CO2 increase, there are good estimates of fossil fuel use going back to 1880 available at CDIAC plus some data of land use contributions to atmospheric CO2.  Using that data I have piece together an approximation of Anthropogenic contributions to CO2.

The typical formula used to calculate CO2 impact is T=5.25*ln(Cf/Ci) where T is temperature in C or K, Cf is the final CO2 concentration and Ci is the initial CO2 concentration.  Ci is generally assumed to be 280 ppmv based on various paleo exidence, primarily ice cores.  Other paleo proxies for CO2 indicate that Ci could be closer to 300 ppmv and there is some uncertainty.

This is what my little comparison of CO2 forcing extended back to 1880 looks like.  The CO2 cocentration from 1959 to present is just the Mauna Loa.  From 1880 to 1959 I used the ratio of the CDIAC fossil fuel plus land use to extrapolate CO2 concentration.  That required an exponential factor (Cf/Ci)^.075 to fit the 1959 CO2 to an approximate preindustrial 280 ppm.

To "fit" the ln(Cf/Ci) to the ERSST data required one main adjustment, I had to use 2.25 instead of the 5.25 multiplier.  I also adjusted the preindustrial concentration to 285 instead of 280 ppm to tweak the fit.   Since pre-industrial is assumed to be normal, I used a 1880 to 1900 baseline for the temperature anomaly.  You can see how the Northern Hemisphere land which has plenty of areas between -18 and 0 C warmed better than the SH and ocean temperature data.  Generally, the more alarmist of the CO2 aficionados will use the most noisy NH land data in an effort to make their case that CO2 is a danger to the world.  CO2 may be a danger, but it appears the danger is a good bit overly stated.

Now for the interesting part,  the 2.25 versus 5.25 is a pretty big difference.  A little less than half of the expected value.  Instead of 3C per doubling the value would be 1.55 C per doubling.  This seems to be the more popular current estimated range for transient climate sensitivity to a doubling of CO2.

Please note that this estimate did not consider any recovery from past ice ages and assumes that 1880 to 1900 is "average". Allowing to amplification due to recovery from a little ice age should reduce the "sensitivity" to 2XCO2 since there would be less of that -18 to 0 C land to warm up. 

Just thought I would share. 

UPDATE:

If you are a fan of the higher sensitivity,

 You can see that the 5.25 multiplier can be useful.  The correlation is not as good, but it does make a nice visual. 

The Elusive Global Surface Temperature

Have I found it?  Likely not.  Since the average altitude of the land mass is 680 meters above sea level and sea level likes to change, there is likely not a meaningful global surface temperature that everyone could agree with.  I personally would like a better estimate of some surface temperature, so I made my own using NOAA's Extended Reconstructed Sea Surface Temperature and the Berkeley Earth Surface Temperature project data to date.  BEST is putting together a combined Land and Ocean data set, but I just could not wait.

Using the Reynold's Optimally Interpolated SST data version 2, so hopefully this version is actually optimum with a baseline from November 1981 to March 2013 I "adjusted" the ERSST data from 1880 to present for 90S to the equator and for the equator to 90N.  Of course as you approach the 90s, data quality gets worse.  I haven't bothered with error bars, but I came up with some numbers.  I did the same thing with the ER land data using a 1951 to 1980 baseline that matched the BEST absolute temperature estimate for the hemisphere land masses.

Tah Dah!  It will probably be obsolete by some time tomorrow, but there it is.  That puts the "average" absolute temperature at about 15.25C with the average SST at about 17.85 C degrees.  Depending on what you would like for your "average" period to be, you can fudge one way or the other.  Since the Land estimate uses the BEST Tave estimated absolute value, this is a mix of some average at some altitude for land with the approximate actual SST instead of some temperature 5 meters or so below the surface.  The numbers in the ledgend are million kilometers square that I used, more precise values are likely available.

The reason I did this nonsense is for this;

This is the meridional differential temperature using the Redneck Physics absolute hemispherical land and ocean absolute approximate average temperature.  For the period 1880 to 2013, the "average" differential temperature between the hemispheres is about 1.1 C degrees which is based on a mean surface temperature of ~15.25 C degrees.  If I smooth out some of that noise, the range is about 0.8 to 1.35 C degrees.  There is a nice swoop or hump from 1880 to 1980 which is the ~ 100 year pseudo cycle I have been trying to isolate a little more accurately.

The reason that is so interesting is that the radiant forcing down or "back radiation" at the upper troposphere to turbopause is the same for both hemispheres.  Corriolis effect tend to isolate the hemispheres somewhat in the atmospheric circulation but forces ocean heat flow north from the Antarctic Circumpolar Current.  There is mechanical pump action messing with the oh so sickeningly sweet ideal radiant "greenhouse effect".

You may notice, if you are a savvy climate fan, that the end swoop starting at about 1985 just happens to correspond with the shift in "global" diurnal temperature trends. 

I just wanted to get this posted since the BEST combined Land and Ocean is supposedly due out any day now and I figure this might be interesting to compare with their results.